Can doctors tell if you smoke from a blood test

Contents

PMC

Cost arguments

An argument made to support the discriminatory non-treatment of smokers is that increased complications lead to additional expenditures that could be avoided if smokers would simply stop smoking. But why focus our cost saving concerns on smokers in the context of surgery? Do patients have a general obligation to get healthy as a condition of receiving treatment? Patients are not required to visit fitness clubs for eight weeks, lose 25 pounds, or take drugs to lower blood pressure before surgery.

Many non-smokers cost society large sums of money in health care because of activities they choose to take part in. “Baby boomers” in the United States lost 488 million days of productivity in 2002 because of sports injuries. From 1991-8 sports related injuries in this age group increased 33% and cost about $18.7bn (£9.6bn; €14bn) a year in medical costs alone.3 We could reduce healthcare expenditure by simply refusing to pay for treating any injuries related to voluntary participation in sports. Let them suffer their painful knee condition which is entirely their fault. Indeed, if we treat a sports injury that person is likely to risk incurring future costly sports injuries. But we don’t even think this let alone suggest it.

Discriminating against smokers has become an acceptable norm. Indeed, at least one group of authors who believe smokers should be refused surgery blithely admits that it is “overtly discriminatory.”4 The suggestion that we should deprive smokers of surgery indicates that the medical and public health communities have created an underclass of people against whom discrimination is not only tolerated but encouraged. When the World Health Organization announced that it would no longer employ anyone who smokes, public health and medical communities did not respond to this act of blatant bigotry.5 6 Similarly, it is shameful for doctors to be willing to treat everybody but smokers in a society that is supposed to be pluralistic and tolerant. Depriving smokers of surgery that would clearly enhance their wellbeing is not just wrong—it is mean.

How Long Does Nicotine Stay in Your System?

Nicotine is the addictive chemical found in cigarettes and other tobacco products. When you smoke, your body breaks down nicotine and turns it into cotinine. Cotinine is the chemical metabolite that lab technicians look for when screening for nicotine use.

The length of time that a drug remains in your body depends on the drug’s half-life, which is the amount of time it takes for 50 percent of the substance to leave your system. Mayo Medical Laboratories states that cotinine has a half-life of about 15 hours, while nicotine has a half-life of about two hours.

In general, nicotine stays in the body longer than LSD, Adderall and methamphetamine. Cotinine can be detected in various test samples, including urine, blood and saliva. But the time it remains detectable in each sample type varies.

How Long Does Nicotine Stay in Your Urine?

Cotinine levels in urine begin to return to normal about seven to 10 days after you last smoked, according to the University of Rochester Medical Center. If you smoke regularly, it may take up to three weeks for the cotinine to clear your system.

Testing urine samples for cotinine is the most widely used method of detection. According to a 2016 study published in the Journal of Clinical & Diagnostic Research, four to six times more cotinine can be found in urine than in blood or saliva.

How Long Does Nicotine Stay in Your Blood?

Nicotine can appear in the bloodstream about an hour after inhalation. A 2017 article reviewed by the College of Medicine at the University of Illinois stated that cotinine can be detected in your blood for up to 10 days after you quit.

Although a blood test is an invasive procedure, measuring cotinine in blood is the most reliable way to detect nicotine use. It is also the preferred method for determining nicotine exposure among nonsmokers.

How Long Does Nicotine Stay in Your Saliva?

Cotinine can be traced in saliva for up to four days after last use, according to a report by Smith County, Texas.

Measuring cotinine in saliva is a noninvasive approach that is well-tolerated by patients. A 2011 study published in the journal Therapeutic Drug Monitoring stated that saliva tests minimize the risk for tampering.

How Long Does Nicotine Stay in Your Hair?

Various drugs, including nicotine, can be found in your hair for up to 90 days after ingestion. Some tests can identify nicotine in your hair for up to a year after last exposure.

Testing for nicotine in hair is not as common as testing urine, saliva or blood. Hair examinations generally cost more. But hair tests have longer drug detection windows than tests of urine, blood or saliva.

Can Secondhand Smoke Show Up On a Drug Test?

Secondhand smoke is exposure to the smoke from someone else’s cigarette. According to the National Institute on Drug Abuse, inhaling secondhand smoke can lead to breathing problems, heart disease and a variety of cancers.

Cotinine can be traced in nonsmokers exposed to secondhand smoke. It can be detected in saliva, blood and urine, according to the Centers for Disease Control and Prevention.

A 2012 study published in the Archives of Pediatrics and Adolescent Medicine examined the prevalence of secondhand smoke exposure in nearly 500 children and infants in a city with a 12 percent smoking rate.

Using plasma testing, evidence of cotinine was detected in 55 percent of the children. Researchers also identified 70 children in the sample who experienced wheezing and possibly developed asthma caused by secondhand smoke.

Factors That Influence How Long Nicotine Stays in Your Body

People break down nicotine at different rates. The time it takes to clear the chemical and its metabolites from the body depends on many factors, including age, sex, diet, type of tobacco product used and history of nicotine use.

The Type of Tobacco Product Used

Some tobacco products introduce more nicotine into your system than others. For example, a 2003 study published in the Indian Journal of Medical Research indicated that cigarette smokers had higher levels of nicotine and cotinine in their system than hookah and bidi smokers.

History of Nicotine Use

Regular smokers break down nicotine more slowly than nonsmokers because tobacco smoke may contain substances that slow down the metabolism of nicotine. Compared to nonsmokers or occasional smokers, it takes people with nicotine addiction longer to eliminate the chemical.

Diet

Food affects nicotine metabolism. A 2005 study published in the American Society for Pharmacology and Experimental Therapeutics found that meals can decrease nicotine concentrations in tobacco users. In fact, 40 percent of nicotine clears from the body after a meal.

Age

The older you are, the longer it can take for nicotine to leave your system. People 65 and older do not metabolize the chemical as quickly as younger people. Reduced blood flow in the liver might contribute to this slower metabolism of nicotine.

Sex

An American Society for Pharmacology and Experimental Therapeutics study indicated that the half-life of cotinine was shorter in women than in men, which suggests that it clears more quickly in women. Pregnancy also speeds up the elimination of nicotine from the body.

If you are addicted to nicotine, the drug may not clear from your system for many weeks. Smoking has a number of health, social and financial consequences, and it can lead to premature death. It is never too late to quit. If you’re ready to commit to a nicotine-free lifestyle, learn more about ways to quit smoking.

Nicotine Tests

Topic Overview

A nicotine test measures the level of nicotine-or the chemicals it produces-in your body. It’s usually done by testing a sample of your blood or urine. The test is used to see if you smoke or use other forms of tobacco.

All forms of tobacco have nicotine. This includes pipe tobacco, cigars, cigarettes, chewing tobacco, and snuff. It also includes e-cigarettes and quit-smoking aids like nicotine gum and nicotine patches.

Your body breaks down nicotine into several chemicals, such as cotinine, that can be found by these tests.

You may be asked to have a test when you apply for a job. And some health and life insurance companies require a test before they take you as a client. This is because people who smoke tend to have higher health costs over the long run.

One type of test can help tell the difference between a person who uses tobacco, a person who recently quit, and a person who doesn’t use tobacco but has been exposed to a lot of secondhand smoke.

If you no longer smoke but are using a quit-smoking aid like gum or a patch, your test result may be positive. But you may be able to get another test that can show that you are using quit-smoking aids and not tobacco.

When you stop using nicotine, it can take more than 2 weeks for the levels of nicotine and cotinine in your blood to drop. It takes a few more weeks than that for the levels in your urine to drop.

Is yearly chest x-ray screening helpful in reducing mortality for smokers?

EVIDENCE-BASED ANSWER

For current and former smokers, the evidence does not support yearly chest x-rays to decrease lung cancer mortality (strength of recommendation : A, based on multiple randomized controlledtrials). Even with the addition of sputum cytology and more frequent chest x-rays, lung cancer mortality was unchanged (SOR: A).

CLINICAL COMMENTARY

Reduce morbidity and mortality by helping patients quit smoking

The bottom line is that morbidity and mortality are not reduced when we use chest x-rays, sputum cytology, or a combination of the 2 in screening for lung cancer. One thing we can do for our patients is counsel them about the ill effects of tobacco use and support them in their smoking cessation efforts. Although there is no guarantee that those who quit will not get lung cancer, cessation certainly reduces the risk and brings other health and financial benefits.

Of interest is the ongoing National Lung Screening trial, which compares screening spiral CT scans with chest x-rays in the detection of lung cancer. This large trial, sponsored by the NCI, will compare both modalities over 8 years and should help determine if either test is better at reducing morbidity and mortality from this disease.

Evidence summary

Five randomized controlled trials have examined lung cancer mortality after screening chest x-rays. In the first trial—the only one that included former as well as current smokers and nonsmokers—subjects were randomized to undergo chest x-ray studies every 6 months, or at baseline and again at the end of the 3-year study. After 3 years, there was no statistically significant mortality difference with more frequent chest x-rays.1,2

Another trial involved male smokers who were randomized to undergo chest x-ray and sputum cytology either every 6 months or after 3 years. After 3 years, both groups were screened annually with chest x-ray alone for an additional 3 years. There was no significant difference in lung cancer mortality at any point, including at a 15-year post-trial follow-up.3Both studies showed earlier detection and longer survivorship of lung cancer among screened vs nonscreened groups due to lead-time bias (because the cancer was detected earlier from screening vs clinical diagnosis, it falsely appears to prolong survival). Overall mortality was the same in both groups.

The National Cancer Institute (NCI) sponsored 3 randomized controlled trials on lung cancer screening for male smokers involving 3 major medical centers. The studies were designed to determine the incremental benefit of adding sputum cytology to chest x-ray screening. In 2 of the NCI studies, participants were randomly assigned to receive annual chest x-ray only or a dual screen with annual chest x-ray and sputum cytologies every 4 months. In both studies, there was no statistical difference in lung cancer mortality between the 2 groups.4-6The third NCI study randomized participants to chest x-ray and sputum cytology either every 4 months or annually. Again, there was no significant difference in lung cancer mortality,4even after an extended follow-up of 20.5 years.7Adding sputum cytology to chest x-ray only improved lung cancer detection rates over chest x-ray alone.

A significant limitation of the 5 studies presented is that no true control or non-screening groups determined the real efficacy of screening chest x-rays vs no screening. The goal of a study of a screening program is to detect a disease early enough so that treatment can alter mortality. These uncontrolled studies of routine screening chest x-rays, no matter how frequently performed, do not meet this criteria for current and former smokers.

Recommendations from others

The US Preventive Services Task Force does not recommend for or against screening asymptomatic or high-risk persons for lung cancer with either low-dose computed tomography (CT), chest x-ray, sputum cytology, or a combination of these tests.8 The American Cancer Society and American Academy of Family Physicians recommend against the use of chest x-ray or sputum cytology in asymptomatic high-risk persons.9,10The American College of Chest Physicians recommends against the use of serial chest x-rays for individuals without symptoms or without a history of cancer.11 They do not comment about high-risk groups—that is, current or former smokers.

Lung structure in healthy neversmokers and smokers assessed by CT-densitometry and chest X-ray

Abstract

Background: Smoking causes inflammation in the lungs, which may lead to structural changes and irreversible airways obstruction, characteristic for COPD. By computered tomography (CT), areas with Hounsfield units (HU) below -950 have been considered as emphysema, while increased attenuation may indicate inflammation. We investigated changes in smokers compared to neversmokers.

Materials and methods: 40 current smokers (35±12 pack-years; mean ± SD) with normal lung function and 36 healthy neversmokers performed chest X-ray and CT. Age was 45-65 years with equal sex distribution. Lungs were defined as voxels with attenuation between -300 to -1024 HU, further divided into eight intervals. Chest X-rays were evaluated according to 4 criteria: depressed diaphragm, irregular radiolucency, abnormal retrosternal space and sternodiaphragmatic angle >90°. Two or more criteria’s was considered as emphysema.

Discussion: Increased lung density in smokers may indicate inflammation but this has to be correlated to other signs of local inflammation. Females may be more vulnerable than males to the effects of smoking. Despite normal lung function, a considerable number of subjects had emphysema on plan chest x-ray. Further analyses are in progress including patients with COPD.

Who Should Be Screened for Lung Cancer?

This decision aidexternal icon from the Agency for Healthcare Research and Quality will help prepare you to talk with your doctor about whether lung cancer screening is right for you.

Lung cancer screening has at least three risks—

  • A lung cancer screening test can suggest that a person has lung cancer when no cancer is present. This is called a false-positive result. False-positive results can lead to follow-up tests and surgeries that are not needed and may have more risks.
  • A lung cancer screening test can find cases of cancer that may never have caused a problem for the patient. This is called overdiagnosis. Overdiagnosis can lead to treatment that is not needed.
  • Radiation from repeated LDCT tests can cause cancer in otherwise healthy people.

That is why lung cancer screening is recommended only for adults who are at high risk for developing the disease because of their smoking history and age, and who do not have a health problem that substantially limits their life expectancy or their ability or willingness to have lung surgery, if needed.

If you are thinking about getting screened, talk to your doctor. If lung cancer screening is right for you, your doctor can refer you to a high-quality screening facility.

The best way to reduce your risk of lung cancer is to not smoke and to avoid secondhand smoke. Lung cancer screening is not a substitute for quitting smoking.

When Should Screening Stop?

The Task Force recommends that yearly lung cancer screening stop when the person being screened—

  • Turns 81 years old, or
  • Has not smoked in 15 or more years, or
  • Develops a health problem that makes him or her unwilling or unable to have surgery if lung cancer is found.

Blood test to help smokers ‘find best way to quit’

Image copyright Thinkstock Image caption Although smoking is becoming less popular in many parts of the world, the total number of smokers is growing

A blood test could help people choose a stop-smoking strategy that would give them the best chance of quitting, research in a Lancet journal suggests.

Studies show as many as 60% of people who try to give up start smoking again in the first week.

But researchers argue measuring how quickly a person breaks down nicotine could boost the chances of success.

Other experts say the cost-effectiveness of these extra tests would need to be assessed.

Patches or pills

Nicotine is one of the most addictive substances in cigarettes – smokers crave more nicotine when their body’s levels drop, prompting them to smoke again.

But different people break down nicotine at different rates.

Some scientists suggest people who break it down more quickly may crave more cigarettes and in turn find it harder to quit.

In this study, researchers from the University of Pennsylvania in the US enlisted some 1,240 people on different smoking cessation programmes.

They checked each volunteer’s blood to see if nicotine was broken down at a normal or slow rate.

Volunteers received either a nicotine patch, a drug called varenicline or treatment with a dummy pill.

Varenicline is a non-nicotine based drug that is available on prescription . Doctors balance potential side-effects – including the risk of depression and suicide – against the harms of continued smoking.

Everyone in the trial had access to behavioural counselling too.

Image copyright SPL Image caption Nicotine replacement can be in the form of patches and sprays

Scientists found people who broke down nicotine at a normal rate had a better chance of quitting while using varenicline than those using nicotine replacement patches.

Though volunteers who broke nicotine down more slowly had similar success rates whichever method they used, they reported more side-effects with the varenicline.

Prof Caryn Lerman, one of the lead researchers, said: “If these tests are used, people could have a sizeable chance of success.

Wider use

“For some people, with normal metabolism of nicotine, the chance of success might be low on the patches but could double if they take the pill while for a third of the population with slower breakdown, cheaper patches might be best.”

Blood tests to check for nicotine breakdown speed are currently used in research but scientists say they could be easily developed for much wider use.

Dr Neil Davies, of the University of Bristol, provided an independent comment: “The results are an important scientific advance.

“If the findings can be replicated they could lead to changes in practice. But there are still questions that need to be answered.

“The cost-effectiveness of these tests would need to be taken into account.”

Prof Robert West, from University College London, who was not involved in this paper, said: “We know that if people try to quit unaided their chance of success for a year is about 4%.

“The way to succeed is to keep trying. It is like rolling a dice. If you keep rolling it you will succeed but if you stop rolling you will fail.”

The University of Pennsylvania research was published in the the Lancet Respiratory Medicine journal.

To perform this study, we received a large administrative dataset of anonymized blood biochemistry and cell count results linked to individuals’ chronological age, sex, and confirmed smoking status. The dataset was representative of the entire Alberta population, both rural and urban, with proportional representation of individuals of all ethnic origins. We then trained a set of supervised feed-forward deep neural networks (DNNs) on the nonsmokers to predict the chronological age (Fig. 1B). Subsequently, we calculated the age of the smokers and nonsmokers excluded from the training. To further investigate the effect of smoking on age prediction, we included smoking status as one of the input features and performed feature importance (FI) analysis. Finally, we trained a set of supervised feed-forward deep neural networks to predict the smoking status of patients using only their blood profiles and sex.

Figure 1

Deep learning-based blood-biochemistry clocks accurately predict chronological age. (A) Prediction accuracy of the best-performing model. The model trained on 24 parameters achieved an R2 of 0.57 and an MAE of 5.7 years. (B) The design of the deep learning study that used blood-biochemistry data to predict an individual’s age. Blood samples of nonsmokers were first preprocessed and normalized as previously described8. Next, arbitrage ranking based on 320 RF models was applied to facilitate the selection of the most appropriate feature space with maximum samples available. Afterward, missing values were reconstructed using an autoregressive model with a view towards increasing the training sets, and the resulting feature sets were used to train and test DNNs for predicting patient age and smoking status. (C) Feature importance plot. Fasting glucose, sex, and RDW exhibited higher relative importance scores than other features used in model training. Note High-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol. RDW for red blood cell distribution width, RBC for red blood cell counts, MCV for mean corpuscular volume, ALT for alanine transaminase, MCHC for mean corpuscular hemoglobin.

Data overview and preprocessing

We obtained data from 149,000 fully anonymized individual records linked to smoking status (49,000 smokers), sex, and age, with up to 66 blood biochemistry and cell count markers (Supp. Table 1). Of the 66 markers, 36 were among the 41 features used to train our previous Aging.AI 1.0 system10. The number of females, males, smokers and non-smokers within each age group was comparable (Supplementary Fig. 1). The median age was 55 years.

DNNs require large training datasets. To obtain a sufficiently large training sets we first selected samples with the same blood test date, that is, datasets consisting exclusively of blood-based biomarkers measured on the same day, so that our DNN could be trained consistently, relevantly, and accurately.

Although deep learning models can automatically extract features from the data and usually outperform shallow machine learning at this task, it is a good practice to select a set of relevant features before training the network. We optimized the feature spaces that were used to train the models for age prediction first excluding smoking status using a multifactorial adaptive statistical arbitrage model13 for subsets of samples with various numbers of measured markers. We trained 320 random forest (RF) models on distinct feature spaces and subsequently extracted FI values from each model. The features were ranked by their relative importance to age prediction according to the scores of the models (Formula 1, Supplementary Fig. 2). The accuracy of any predictor depends on the sample size and the feature space on which it is trained. To supplement the number of features used to train our predictors, we applied linear regression to fill missing values for 30–60% (depending on the feature type) of the samples in the dataset. This reconstruction successfully increased the number of available features from 14, 15, and 18 to 18, 20, and 23 features, respectively.

The blood marker with the largest contribution to the age-prediction model is glycated hemoglobin (hemoglobin A1c), followed in descending order by blood urea, fasting serum glucose, and serum ferritin (Supplementary Fig. 2). Fasting glucose was among the most important features in our previous studies on deep learning-based hematological aging clocks10,11.

Interestingly, the most important markers (as selected by the arbitrage FI method) demonstrate independent weak biweight mid-correlation, which shows the strength of a linear association between blood markers and age. The arbitrage FI method is more robust than the Pearson correlation coefficient, being a median-based measure that is less sensitive to outliers (Supplementary Fig. 3, Table 2).

Deep-learned blood-biochemistry clocks can effectively predict biological age

Using the FI ranking determined by the RF models, we selected three different sets of blood biochemistry and cell count markers (Supplementary Table 3). Input feature sets were chosen to contain the maximum number of available samples that displayed the features selected via RF-based arbitrage feature selection previous section).

To predict individual age, we trained three DNNS on selected blood test input features of nonsmoking subjects. The predictive performance of each model was evaluated using the Pearson correlation coefficient (r), the standard coefficient of determination (R2), and the mean absolute error (MAE) (Formulae 2–4).

All three models achieved a relatively high correlation between predicted and actual chronological age. The best-performing model was the deep neural network trained on 23 blood test input features (MAE = 5.72 years, R2 = 0.56). The deep neural network trained on 20 blood test input features achieved an MAE of 5.78 years and an R2 of 0.578, followed by the deep neural network trained on the 18 available blood test input features, which achieved an MAE of 5.898 years and an R2 of 0.55 (Fig. 1A, Supplementary Fig. 4A,B, Table 1). Samples from the tail ends of the distribution (individuals younger than 35 years and those older than 75 years) exhibited a higher error rate for age prediction. Fasting glucose, sex, and red blood cell distribution width (RDW) were predicted to be the most important markers (Fig. 1C, Supplementary Fig. 4C,D).

Deep-learned biochemistry clocks reveal differences in the biological ages of smokers and nonsmokers

To investigate the effect of smoking on age prediction, we used neural networks trained on nonsmokers to calculate the age of the smokers and nonsmokers excluded from the training set. Model demonstrated R2 of 0.57 in predicting non-smokers and R2 of 0.55 in predicting smokers. We also calculated the log2 aging ratio (Formula 5) as proposed by Hannum et al.14. Compared with nonsmokers, smokers showed an accelerated rate of aging through to age 55 years regardless of sex (Figs 2B and 3, Supplementary Fig. 8). After age 55, these differences disappeared and perhaps even reversed themselves for the most elderly subjects (Figs 2B and 3, Supplementary Table 4). In the context of biological aging, this suggests that the contribution of tobacco smoking as an external factor of aging may eventually be masked by the intrinsically stochastic and physiologically deleterious nature of the aging process. Alternatively, the people most affected by smoking may have died at an earlier age and thus were be excluded from the old-age smoking group.

Figure 2

Deep learning-based hematological clocks demonstrated accelerated aging rates in smokers and revealed patient smoking status. (A) The prediction accuracy of the best-performing model trained on feature space extended with smoking status. The model, trained on 24 parameters, achieved an R2 of 0.60 and an MAE of 5.42 years (B) The log2 aging ratio of smokers to nonsmokers by age and sex groups for the best-performing model. Smokers demonstrated a higher aging rate regardless of sex. However, these differences plateaued after 55 years of age. A log2 aging ratio of 1 means the sample was predicted to be twice as old as a chronological age, and a log2 aging ratio of −1 means the sample was predicted to be half as old as a chronological age. (C) The most important features in the classification of smoking status selected by the PFI method. HDL cholesterol, sex, and hemoglobin exhibited higher relative importance scores than other features used in model training. (D) The model trained on 23 parameters achieved an F1 score of 0.67 and an accuracy of 0.84. Note High-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol. RDW for red blood cell distribution width, RBC for red blood cell counts, MCV for mean corpuscular volume, ALT for alanine transaminase, MCHC for mean corpuscular hemoglobin.

Figure 3

Confusion matrices. (A) Confusion matrices for the best-performing smoking status classifier, trained on 23 features, in number of samples (left) and percentage (right). Row values show predicted smoking status, and columns show actual smoking status. Most of the error smoking predictions occurred in individuals older than 55 years. (B) Confusion matrices for age prediction by age groups for the best model, trained on 24 parameters, in number of samples (left) and percentage (right). Row values show actual chronological age group, and columns show predicted age group. Smokers of age groups < 30 and 30–40 were mostly predicted to be older.

To further evaluate the importance of smoking status in age prediction we included smoking status as an input feature along with blood test values and trained the new set of DNNs on the three extended sets of input features. Smokers were included in the training set for this round. To robustly compare the performance of these models with models trained on nonsmokers, we used the same number of samples in the training sets. The best-performing deep neural network, which was trained on 24 blood test input features, performed better than the model trained on 23 input features (without smoking status) and achieved an R2 of 0.60 and an MAE of 5.42 years (Fig. 2A, Table 1). Deep neural networks trained on 21 and 19 blood test input features also exhibited higher age-prediction accuracy than the models trained on 20 and 18 blood test input features, respectively (Supplementary Figs S5A and S5B, Table 1). These results suggest that smoking status plays an important role in predicting age. However, this feature was not among the five most important features (Supplementary Figs S5C, S5D and 5E). To evaluate the dependence between age prediction as a target function and smoking status, we conducted a partial dependence analysis that confirmed predicted age increase with a smoking status of 1 (smokers) (Supplementary Figs 7–9). The same analysis of sex as an input feature showed that predicted age increases slightly with a sex of 1 (male) (Supplementary Fig. 9).

Table 1 Prediction accuracy of the three top-performing models after rounds of optimization.

Deep-learned biochemistry clocks as biomarkers of lifestyle

To explore whether the smoking status of patients could be assessed using only patient sex and their blood test values we trained three DNNs on the same input feature sets used in the prior models to classify smokers and nonsmokers. The best-performing smoking status classifier, which was trained on 23 blood test input features, achieved an accuracy of 0.83 and an F1 score of 0.67, followed in descending order by the model trained on 20 blood test input features, and the model trained on 18 blood test input features (Fig. 2D, Supplementary Figs 6A,B, Table 1). High-density lipoprotein (HDL) cholesterol, hemoglobin, RDW, and mean corpuscular volume (MCV) were consistently the most important factors in determining a patient’s smoking status (Fig. 2C, Supplementary Fig. 4C,D).

Curiously, most of the false-positive and false-negative smoking status predictions occurred in individuals older than 55 years (Fig. 3A). This observation was consistent with the increased error rate that accompanied predictions of the ages of smokers and nonsmokers who were chronologically younger than 40 years. Furthermore, the majority of smoker samples for individuals younger than 30 years were predicted to be within the range of 31–40 years (35%) and 41–50 years (36%), whereas the ages of most of the nonsmokers (62%) were predicted correctly (Fig. 3B). The same trend was observed for the 31–40 age group, in which the ages of 43% of the smokers were predicted to be 41–50, and only 23.43% of nonsmokers were predicted to fall within the 31–40 age group. This trend was not observed in subjects older than 51 years and was therefore consistent with the observation made above.

Cardiovascular disease risk and smoking status

To assess the cardiovascular risk values, we examined the cholesterol ratio, which was calculated by dividing total cholesterol by HDL cholesterol (cholesterol ratio = total cholesterol/HDL cholesterol). We classified the blood samples into four groups based on their cholesterol ratios and fasting glucose levels, using the following reference ranges: (1) cholesterol ratio > 4 and fasting glucose >5 mmol/L; (2) cholesterol ratio > 4 and fasting glucose ≤ 5 mmol/L; (3) cholesterol ratio 4 and fasting glucose > 5 mmol/L; and (4) cholesterol ratio ≤ 4 and fasting glucose > 5 mmol/L. As shown in Fig. 4, smokers had a higher log2 aging ratio than did nonsmokers regardless of their cholesterol ratio and fasting glucose levels. On average, female smokers were predicted to be twice as old as their chronological age as compared to non-smokers. Male smokers, on average, were predicted to be one and a half times as old as their actual chronological age compared to nonsmokers. However, females with cholesterol ratio > 4 and fasting glucose < 5 mmol/L tended to be predicted as being older. Interestingly, our results also suggest that smokers from the age groups 60–70 years and >70 years with a normal glucose level (<5 mmol) are predicted to be younger than their chronological age. This phenomenon is not observed in smokers with a high blood glucose level.

Figure 4

Log2 aging ratios for the four groups Cholesterol ratio > 4 and Fasting Glucose > 5 mmol/L, Cholesterol ratio > 4 and Fasting Glucose <= 5 mmol/L, Cholesterol ratio <= 4 and Fasting Glucose > 5 mmol/L, and Cholesterol ratio > 4 and Fasting Glucose > 5 mmol/L. Smokers of age groups < 30 and 31–40 are predicted older regardless their Cholesterol ratio and Fasting Glucose level. Log2 aging ratio of 1 means that sample is predicted two fold older than a chronological age and log2 aging ratio of −1 means sample is predicted half as old. Bars indicate standard deviation.

How long does nicotine stay in your system?

As a smoker, finding insurance can be frustrating because the lowest rates go to nonsmokers. Smokers are classified as high-risk applicants, and they’ll most likely charge you higher premiums. One solution is to simply quit smoking. However, that’s easier said than done.

Here’s how long you’ll need to wait until nicotine fully leaves your system, opening up the possibility of passing your provider’s test.

How long can I expect nicotine to show up on a test?

It takes at least three days for nicotine to leave your blood, however, providers test for another compound — cotinine — that’s formed after nicotine enters your body. Cotinine can stay in your body for up to three weeks or longer.

Different tests are used to determine whether you have nicotine or cotinine in your system. Some are more sensitive than others, measuring the concentration of compounds in your system to determine whether you’re a smoker or simply live with one.

Types of nicotine tests

For a typical test, a medical professional takes a bodily sample to test for nicotine or cotinine. Here are four tests you might encounter.

  • Urine test. The most common, this test is used to gauge cotinine levels, detecting nicotine for up to a week after it was absorbed into your bloodstream.
  • Saliva test. Less common, a saliva test can detect nicotine over a longer period of time. Your medical professional may ask you to take this in conjunction with the urine test for more accurate results.
  • Hair test. A highly accurate test, this one’s expensive. Your insurer may ask you to take it only in special circumstances. It can detect nicotine one to three months after you’ve stopped smoking — and sometimes longer.
  • Blood test. Very rarely, your insurer will ask you to take a blood test. It’s extremely accurate as long as it’s given within its detection window — one to three days for nicotine and one to 10 days for cotinine.

Nicotine may stay in your system longer depending on your age, your health, how long you’ve been smoking and other factors.

Certain the nicotine is out of your system?

Find a life insurance policy that will offer you the best rates today.

Your information is secure.

Is there a way to guarantee I’ll pass a nicotine test?

Unfortunately, the only way to guarantee passing is to quit smoking.

Let us remind you: Quitting your nicotine habit before applying for life insurance does not mean that you’ll pass a nicotine test. Your ability to pass depends on many factors that include your health, how long you’ve been smoking, your smoking frequency and your overall diet.

If you’re committed to staying tobacco-free, you might be able to help your body rid itself of nicotine and cotinine faster by embracing a few key changes to your diet and lifestyle.

For example, consuming Vitamin C can help flush nicotine from your bloodstream. Plus, eating more fruits and vegetables might help decrease your cravings for cigarettes. Broccoli, spinach, kiwis and oranges are fine choices.

Can I test my own nicotine levels?

Yes. You can buy nicotine test kits to use at home. They’re fairly easy to use, because they just need samples of your urine. They also tend to be fairly inexpensive.

Though home test kits may not give you a definitive reading, they can give you more confidence that a medical exam won’t detect nicotine in your system.

What if I don’t pass a nicotine test?

If you have a strong feeling you won’t pass a nicotine test, consider applying later. If you can manage, waiting a month or more will greatly increase your odds of passing a nicotine test. That increases your chances of a better health profile.

You’re never obligated to purchase a life insurance policy. So if you do take the health exam and you’re classified as a smoker, you can pass and buy insurance when you’re more certain your body is clean.

Compare rates from these life insurance companies

Like all businesses, life insurance companies are designed to make a profit. They can’t escape basic math: They have to pull in more money than they lose.

Let’s say an insurer collects $20 million in premiums for the year. If it pays out claims that year totaling less than that amount, it makes a profit. If it pays out more than $20 million, it’s in the red — a net loss.

That’s a constant concern for life insurance companies — considering how much they should charge in premiums, balancing that with the likelihood they’ll have to pay out death benefits.

What is a death benefit?

“A death benefit is the money paid out by a life insurance policy when a policyholder dies. This money is paid to the policy’s beneficiaries — or the people designated to receive the death benefit.”

The biggest question a life insurer considers is the likelihood a policyholder will die. Providers calculate this likelihood using multiple health and lifestyle factors.

Advanced age is just one — older people are statistically more likely to pass away. So are people who have cardiovascular disease, high cholesterol or dangerous hobbies.

The same goes for smokers, whose average life expectancies can be some 10 years shorter than nonsmokers.

Insurance companies typically administer nicotine tests to identify those who use tobacco products, and they often charge these individuals higher premiums.

No-medical-exam life insurance

What if your life insurance provider doesn’t require a medical exam? Couldn’t you get a policy without having to admit you’re a smoker?

You might find a policy called no-exam life insurance. Unfortunately, these policies may still require you to complete a questionnaire about your health.

That includes whether you smoke — and it’s best to tell the truth.

Ultimately, you shouldn’t buy no-exam insurance to hide the fact that you’re a smoker. More likely, you’d buy it because you’re in poor health and have difficulty getting a policy that requires a medical exam.

With no-medical-exam insurance, your premiums are often higher because your insurer has less information about your health to work with. Also, there’s a good chance your death benefit will be less than $100,000.

No-medical-exam life insurance providers

Medical exam required? Medical records from doctor required? Coverage
5 Star Life Insurance Company None for policies of $150,000 and under. No $10,000–$100,000
American National No May be required $50,000–$250,000
Assurity No May be required $50,000–$350,000
Fidelity Life No No Up to $250,000
North American Company No No $50,000–$500,000
Phoenix No May be required $50,000–$500,000
Sagicor No No $50,000–$500,000
Transamerica No May be required $25,000–$249,999
Mutual of Omaha None for policies under $250,000. May be required $50,000–$250,000
Lincoln Financial Group No, generally — but depends on your health profile May be required $100,000–$500,000

How upfront should I be about my nicotine use?

It’s understandable to want the lowest premium possible. But it’s always a good idea to tell the truth about your smoking.

First, it’s illegal to lie about your smoking when applying for life insurance. And second, you don’t want the awkward situation of a nicotine test giving you away after you’ve said you were tobacco-free.

One of the biggest reasons to be truthful, however, is because it could affect your beneficiaries. If your insurer later discovers that you were a smoker when you claimed you weren’t, it could deny paying out your death claim benefit to the loved ones you’ve designated to receive it.

Alternatively, your insurer could choose to pay the death benefit that your premium payments would have purchased at the smoker’s rate.

Do “celebratory cigars” affect my health insurance premium?

As the term implies, a celebratory cigar is a cigar you smoke on a special occasion — for example, at a wedding or New Year’s party. If you puff a cigar once in a while, you might wonder whether that makes you a smoker to your insurer.

Some insurers will give you the smoker’s rate if you consume cigars. However, others will classify you as a “non–tobacco user” as long as you smoke under a specified number of cigars a month. For some companies, that’s one a month.

Insurers like ING and AIG tend to offer low rates to people who admit to smoking celebratory cigars. As always, compare quotes among insurers to find the best rate. You may find that an insurer offers a better rate for your age and health.

Bottom line

Buying insurance as a smoker can be frustrating because insurers are more likely to charge you higher premiums. There’s little you can do about that if you keep receiving the “smoker” classification.

However, you can wait to apply when you have a better health profile. By consuming food and beverages high in vitamin C, you can flush out nicotine quicker. And if you’re unsure about your ability to pass a nicotine test, you can buy home test kits to increase your confidence. To find out more, read our guide on life insurance for smokers.

Find a life insurance policy that will offer you the best rates today.

Your information is secure.

Frequently asked questions

  • Where can I learn more about no-exam life insurance?

    Read our guide on no-exam life insurance, which includes types you might encounter and how to apply.

  • Where can I find the best life insurance rates as a smoker?

    Banner and Transamerica tend to offer strong rates for smokers. Consider comparing multiple providers to find the best premiums.

Smokers, It’s Later than You Think

Smokers often believe the damage smoking does to lungs is years away. The results from a new study paint an entirely different picture.

Researchers report that physical exams, lung function tests and chest x-rays are not sensitive enough to pick up early damage from smoking. In the study, 31 smokers who tested normal in every other way showed genetic changes in their lungs similar to those found in people with lung cancer. The findings suggest that lung damage is occurring much earlier than it is generally thought to be in smokers.

When you smoke a cigarette, some of the genetic programming of your lung cells is lost. Your cells take on the appearance of a more primitive cell. It doesn’t necessarily mean you will develop cancer, but that the soil is fertile to develop cancer.

Cells lining the airways of the smokers’ lungs, human embryonic stem cell genes had, according to the scientists, been turned on. These genes are normally active (turned on) in the developing embryo before cells are programmed with their specific assignment. The genes are then turned off as cells become specialized and normally will remain turned off for the rest of a person’s life. But in all major lung cancers they are turned back on.

ADVERTISEMENT “The study doesn’t say these people have cancer, but that the cells are already starting to lose control and become disordered,” Dr. Ronald G. Crystal, the study’s senior investigator and professor of genetic medicine at Weill Cornell Medical College said in a statement. “The smoker thinks they are normal, and their doctor’s exam is normal, but we know at the biologic level that all cigarette smokers’ lungs are abnormal to some degree.”

To paraphrase Yogi Berra — it gets late real early once you start smoking.

In the study, 21 healthy nonsmokers were compared to 31 smokers who had no lung disease symptoms and had normal X-rays, as well as normal chest examinations. By sending a thin tube called a bronchoscope and a fine brush into the lungs, investigators gently brushed the inside of the airways to collect cells from the airway’s epithelium (lining), the lungs’ frontline defense against all invaders, including smoke particles. Researchers then genetically analyzed these cells, which are where lung cancer often begins. And they found noticeable changes.

“When you smoke a cigarette, some of the genetic programming of your lung cells is lost,” Dr. Crystal explains. “Your cells take on the appearance of a more primitive cell. It doesn’t necessarily mean you will develop cancer, but that the soil is fertile to develop cancer.”

One reason younger people smoke is that they think they have time to quit later on before smoking does any significant damage. But research continues to find good reasons for quitting early. A study published earlier this year in the New England Journal of Medicine found that quitting smoking between the ages of 25 and 34 will add an average of ten years to your life.

ADVERTISEMENT Even if you happen to be over 60, there are still many health benefits awaiting you after you stop smoking.

The study is published online in Stem Cells and will also appear in a future print issue of the journal.

A low-dose spiral CT scan is a type of medical test. It is used to look for early signs of lung cancer. If the test finds cancer, treatment can start early.

But the test is not helpful for light smokers or people who quit smoking more than 15 years ago. And it’s not usually recommended for people younger than age 55 or older than 80.

Even heavy smokers get only a small benefit from the test. So you should think twice before you get the test. Here’s why:

The test may help people at high risk.

Studies show a slight benefit from CT scans for:

  • People ages 55 to 80 who smoke heavily (about one pack per day for at least 30 years or 2 packs per day for at least 15 years) AND are either still smoking or have quit within the past 15 years.

If 1,000 high-risk smokers get the test, about three will find lung cancer early enough to receive treatment and not die from lung cancer. Eighteen others will also find lung cancer, and will die even though they had the screening test.

The test doesn’t help people at low risk.

CT scans have no benefits for people with low risk. Research has not shown that the test helps save lives in low-risk groups.

The test creates false alarms.

CT scans cause many false alarms, even in high-risk people. If 100 high-risk smokers get the test, about 40 will show something that can cause concern. But only two or three actually have lung cancer.

The false alarms often lead to follow-up tests. Usually, you need to get several more CT scans. Or you may need a biopsy, or even surgery. This can sometimes cause complications, like bleeding or a collapsed lung.

If your risk is low, a false alarm causes unnecessary worry.

CT scans expose you to radiation.

A low-dose spiral CT scan uses about 20 times more radiation than a standard chest X-ray. The more radiation you get, the higher your risk of getting cancer. So, it’s good to avoid radiation when you can, even if a single dose is low.

The test is expensive.

A spiral CT scan costs $300 or more. Insurance usually pays for the test for lung cancer screening only if you have a very high risk for developing lung cancer. And the test often leads to other costs. Many people have false alarms that lead to more tests and procedures.

When is a CT scan worth the risks?

You should consider getting a CT scan if:

  • You are 55 to 80 years old AND
  • You have smoked heavily for years (about one pack a day for at least 30 years, or two packs a day for at least 15 years) AND
  • You are still smoking or have quit less than 15 years ago.

In high-risk smokers, the benefits of CT scans may be greater than the risks.

The best way to prevent lung cancer.

If you want to prevent lung cancer, quit smoking. Quitting greatly reduces your risk of lung cancer. Your doctor can help you quit, or you can call 1-800-QUIT-NOW. Avoid secondhand smoke, which also increases your risk.

This report is for you to use when talking with your health-care provider. It is not a substitute for medical advice and treatment. Use of this report is at your own risk.

© 2018 ABIM Foundation. Developed in cooperation with the American College of Chest Physicians/American Thoracic Society.

None of the studies included people who never smoked. Although non-smokers can develop lung cancer, there is not enough evidence to know whether screening them would be helpful or harmful. Likewise, it is not known if screening would help people who were lighter smokers than those in the studies, or those of different ages. That’s why the American Cancer Society guideline doesn’t recommend screening for these groups.

High-risk patients should consider getting screened

There are risks associated with low-dose CT scanning, and the possibility of doing more harm than good for people who are less likely to have lung cancer. Because of this, the American Cancer Society recommends people who are at highter risk for lung cancer talk to their doctor who can help them make an informed decision about whether to get screened. If people do decide to get screened, they should get screened every year through age 74, as long as they are still healthy.

One drawback of this test is that it also finds a lot of abnormalities that have to be checked out with more tests, but that turn out not to be cancer. (About 1 out of 4 people in the NLST had such a finding.) This may lead to additional tests such as other CT scans or more invasive tests such as needle biopsies or even surgery to remove a portion of lung in some people. These tests can sometimes lead to complications (like a collapsed lung) or rarely, death, even in people who do not have cancer (or who have very early stage cancer).

LDCTs also exposes people to a small amount of radiation with each test. It is less than the dose from a standard CT, but it is more than the dose from a chest x-ray. Some people who are screened may end up needing further CT scans, which means more radiation exposure. When done in tens of thousands of people, this radiation may cause a few people to develop breast, lung, or thyroid cancers later on.

American Cancer Society Guideline

The American Cancer Society recommends yearly lung cancer screening with LDCT scans for people who are 55 to 74 years old, are in fairly good health, and who also meet the following conditions:

  • Are current smokers or smokers who have quit in the past 15 years.

and

  • Have at least a 30 pack-year smoking history. (This is the number of years you smoked multiplied by the number of packs of cigarettes per day. For example, someone who smoked 2 packs per day for 15 years has 30 pack-years of smoking. A person who smoked 1 pack per day for 30 years also has 30 pack-years of smoking.)

and

  • Receive counseling to quit smoking if they are current smokers.

and

  • Have been told by their doctor about the possible benefits, limits, and harms of screening with LDCT scans.

and

  • Have a facility where they can go that has experience in lung cancer screening and treatment.

Medicare covers screening

The Centers for Medicare and Medicaid Services (CMS) decided low-dose CT will be reimbursed once a year for Medicare patients who are eligible for lung cancer screening. People must be 55 to 77 years old, have at least a 30 pack-year history of smoking, and currently smoke or have quit within the past 15 years.

Because lung screening is recommended by the US Preventive Services Task Force (USPSTF), private insurers have also begun covering the tests. However, the criteria for screening eligibility are slightly different. For example, USPSTF guidelines call for screening up to age 80.

Quitting is still best

Screening is not a substitute for quitting smoking. The most effective way to lower lung cancer risk is to stay away from tobacco.

Signs and symptoms of lung cancer

Although it is not common, lung cancer sometimes causes symptoms in the early stages. Most of the symptoms are more likely to be caused by something that isn’t lung cancer. But it’s important to go to the doctor so the cause can be found and treated. And if it does turn out to be lung cancer, it might be diagnosed at an earlier stage, when treatment is more likely to be effective.

The most common symptoms of lung cancer are:

  • A cough that does not go away or gets worse
  • Chest pain that is often worse with deep breathing, coughing, or laughing
  • Hoarseness
  • Unexplained weight loss and loss of appetite
  • Coughing up blood or rust-colored sputum (spit or phlegm)
  • Shortness of breath
  • Feeling tired or weak
  • Infections such as bronchitis and pneumonia that don’t go away or keep coming back
  • New onset of wheezing

An easy scan for past and present smokers can detect lung cancer while it’s still treatable

If you smoke, quit! It is the single best thing you can do for your health. If you already quit, keep up the good work.

Whether you’re a past or present smoker, the habit has put you at a higher risk for lung cancer. Therefore, you might want to consider a quick, easy screening test.

Past and current smokers can benefit from an easy CT scan that detects lung cancer early.

Susan Edwards is the Imaging Center manager at Regional One Health’s East Campus. Her team offers a CT scan for smokers to check the lungs for possible red flags.

“It’s a low-dose lung screening,” Edwards said. “It’s great for early detection, which can allow for early treatment.”

She said the test is the best option for early screening. Chest X-rays are not considered as effective in looking for lung cancer.

And screening is important:

“Lung cancer often doesn’t cause symptoms until it is advanced and hard to cure,” Edwards explained. Screening can identify a problem early when treatment is more effective.

“We suggest patients who smoke or who used to smoke talk to their doctor about it,” Edwards said. “Your doctor has to order the test for you, and you need to meet certain criteria in order for your insurance to potentially cover it.”

Generally, those criteria include:

  • You are or were a regular smoker (defined as the equivalent of smoking a pack a day for a year)
  • You currently smoke or quit within the last 15 years
  • You’re between age 55 and 80

    Radiologists read the scan to look for concerning nodules. They pass along the results to the ordering physician to discuss with the patient.

  • You currently have no signs or symptoms of lung cancer

Your physician will do a lung cancer screening prior to ordering the test. He or she will counsel you about your lung cancer risks.

If your doctor does order the test, here’s what to expect:

The test itself is quick and easy. “It takes maybe 5 minutes, and it’s completely painless. There’s no contrast to take orally or by IV,” Edwards said.

Like with any CT scan, patients lie flat and still on a table. The machine passes over them to take detailed pictures of the lungs. A radiologist reviews the images to look for nodules.

“If the radiologist sees something, that information is sent back to the ordering physician, who then manages your care,” Edwards said.

The East Campus Imaging Center has appointments available for CT lung cancer screenings.

A “positive” test means the scan showed a nodule of a concerning size. Your doctor may order additional screening or other tests, like a biopsy.

The test can also be “indeterminate.” Your doctor might recommend monitoring and additional imaging at a later time.

A “negative” test means your lungs appear normal. Still, high-risk patients should be screened annually, Edwards said. The screening is discontinued once it has been more than 15 years since a patient quit smoking.

Edwards said patients who are screened at the East Campus can expect their results to be read by their doctor within 48 hours.

A test called CT lung cancer screening could save the lives of tens of thousands of American smokers and former smokers every year, but only only 4% of those eligible are getting it.

One such patient, a 58-year-old woman I’ll call Marie, battled cigarette smoking for over three decades before finally quitting on her 50th birthday. A few years later, Marie had the test, and the radiologist found an 8 millimeter nodule in her right lung, which proved to be a small cancer. She had the tumor removed, and now she is five years out from surgery, with no signs of cancer. In two months, she will welcome her first grandchild.

Marie’s story is not unusual. While U.S. smoking rates have fallen to a historic low, 38 million Americans still smoke. Men who currently smoke have a risk of lung cancer about 23 times that of nonsmokers, while the risk for women is about 13 times higher. Naturally, the best thing smokers can do to lower their risk of lung cancer is to quit, but the increased risk of cancer does not disappear immediately. It gradually declines over decades.

Battling lung cancer matters, because it is the number one cancer killer in the U.S., causing an estimated 154,000 deaths a year – more than all colon, breast and prostate cancer deaths combined. The American Lung Association estimates that 234,000 Americans will be diagnosed with lung cancer this year, 85% of whom will have been cigarette smokers.
Five-year survival rates are about 19%, which is relatively poor compared to most other cancers, such as breast and prostate. Until recently, this has meant that the only highly effective means of combating mortality is smoking avoidance. But now there is a new tool for reducing death rates even among smokers.

CT screening

As a radiologist, I am familiar with CT lung cancer screening. CT stands for computed tomography, a sophisticated type of X-ray imaging. When lung cancer is diagnosed at an early stage, long-term survival is 70%, compared to only 5% when it has spread to other parts of the body. Its value was established in the National Lung Screening Trial, a US$300 million National Cancer Institute study launched in 2002 that followed 53,000 current or former smokers for five years. Investigators found a 20% mortality reduction among those screened by CT. A more recent Japanese study showed a 51% reduction in mortality.

CT scanning is not new. It was invented in the 1960s by a British engineer, Godfrey Hounsfield, who shared the 1979 Nobel Prize in Physiology or Medicine for it. Unlike standard X-ray imaging, which sends X-rays through the patient in only one direction, CT transmits and detects X-rays in many different directions, dramatically improving imaging of the body’s interior.

A type of lung cancer cell reflective of adenocarcinoma, one of many types of lung cancer cells. David Litman/.com

Like any cancer, lung cancer consists of abnormal cells that proliferate in an uncontrolled fashion, do not obey normal signals to die and cannot repair their DNA. Normal lung cells become cancerous through exposure to tobacco smoke, radon gas, asbestos or airborne pollutants.

In recent years, low-dose CT has begun to be used to screen for lung cancer. Regular chest X-rays detect lung cancers only when they measure centimeters in diameter – the size of a penny or bigger – but CT can find them much earlier, when they are only millimeters wide. As with any cancer, early detection is key to improved survival. Unfortunately, once lung cancer causes symptoms – such as persistent cough, coughing up blood, and weight loss – it has already reached an advanced stage. These newer CT scans also use a lower dosage of X-rays, lowering the risk of causing other health problems.

Saving lives

The U.S. Preventive Services Task Force recommends annual low-dose CT screening in adults between the ages of 55 and 80 who have a 30 pack-year smoking history – meaning that they have smoked the equivalent of one pack a day for 30 years, two packs per day for 15 years, and so on. This includes current smokers and those who have quit within the past 15 years.

The benefits of CT lung cancer screening depend on the population in question. There appears to be no benefit to screening people who do not have an increased lung cancer risk, such as nonsmokers. On the other hand, the benefits of screening appear to be highest in those at highest risk for lung cancer – in other words, those who have smoked the most cigarettes. With more research, it is possible that these screening guidelines will be modified.

So why are only 4% of patients being screened? One barrier is cost: Some patients lack insurance, and others may face high deductibles and copayments. Depending on location, costs can range from hundreds of dollars to a few thousand dollars. Another factor is the anxiety associated with a positive result. Yet another is education – many patients and even some physicians simply don’t know about the test, and even patients who do may decline to undergo it.

By spreading the word about CT lung cancer screening, my colleagues and I hope to save many more lives like Marie’s. By and large, lung cancer is only curable when detected early. Current and former smokers wondering if this test is right for them should talk with their doctor.

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