Long-Term Lung Damage Found In Ex-Smokers, Light Smokers

People who are former smokers or who smoke fewer than 5 cigarettes a day were shown to have long-term damage to their lungs, which can increase the risk of developing chronic obstructive pulmonary disease (COPD), according to a study published in The Lancet Respiratory Medicine.

Researchers sought to determine whether lung function, the amount of air a person can breathe in and out, was compromised among former smokers and light smokers (those who smoke fewer than 5 cigarettes per day). These groups now outnumber current smokers in many developed countries, with some data suggesting that lung function decline ceases and normalizes after smoking cessation. There is information in mechanistic studies that shows the continued decline of lung function among these populations, and the authors hypothesized that former and light smokers could have accelerated lung function decline compared to those who have never smoked.

The analysis included information on 70,228 spirometry exams completed in 6 US population-based cohorts included in the National Heart, Lung, and Blood Institute study. Two cohorts recruited young adults of 17 years or older, 2 recruited middle-aged and older adults of 45 years or older, and 2 recruited elderly adults of 65 years or older, representing an overall 25,352 participants studied from 1983 to 2014. They analyzed forced expiratory volume (FEV₁) decline in sustained former smokers and current smokers compared to that of never smokers through mixed models adjusted for sociodemographic and anthropometric factors, as well as differential FEV₁ decline according to duration of smoking cessation, number of pack-years, and current cigarette consumption.

After adjustment, former smokers were shown to have an accelerated FEV₁ decline of 1.82 mL per year (95% CI; 1.24-2.40) compared to never-smokers, which was 20% of the effect estimate for current smokers (9.21 mL per year; 95% CI, 1.24-2.40). This accelerated FEV₁ decline persisted in former smokers for decades after smoking cessation, as it did in light smokers (those with fewer than 10 pack-years). The effect estimates for FEV₁ decline in light smokers was 68% of that in current smokers consuming 30 or more cigarettes per day (light smokers: 7.65 mL per year; 95% CI, 6.21-9.09; current smokers: 11.24 mL per year; 95% CI, 9.86-12.62).

Estimates of FEV₁ in light smokers represented a 5-fold greater decline when compared to former smokers (1.57 mL per year; 95% CI, 1.00-2.14).

Lead study author Elizabeth Oelsner, MD, Herbert Irving assistant professor of medicine at Columbia University Vagelos College of Physicians and Surgeons, stressed that while “many people assume that smoking a few cigarettes a day isn’t too bad,” the study findings show that the “difference in loss of lung function between someone who smokes 5 cigarettes a day versus 2 packs a day is relatively small,” said Oelsner. “Smoking a few cigarettes a day is much riskier than a lot of people think...everyone should be strongly encouraged to quit smoking, no matter how many cigarettes per day they are using,” said Oelsner.

The lasting impact that smoking has on lung function represents a greater risk for light and former smokers of developing COPD. As light smokers were shown to have an accelerated decline in lung function, Oelsner notes that risk assessments need to be expanded to account for and improve treatment within these at-risk populations. “In the future, if we find therapies that reduce the risk of developing COPD, everyone at increased risk should benefit,” said Oelsner.

Reference

Oelsner EC, Balte PP, Bhatt SP, et al. Lung function decline in former smokers and low-intensity current smokers. [published online October 9, 2019]. Lancet Respir Med. doi: 10.1016/S2213-2600(19)30276-0.