Light smokers more likely than past heavy smokers to develop lung disease
Long-term light smokers were at greater risk for obstructive lung disease, emphysema and lung function decline than heavy smokers who quit, according to findings recently presented at the American Thoracic Society 2018 International Conference.
“Current literature is limited by a reliance on imprecise measurement of smoking exposure,” according to the abstract.
Researchers, led by Amanda R. Mathew, PhD, a research assistant professor of the preventive medicine department at Northwestern University Feinberg School of Medicine, prospectively analyzed annual smoking behavior assessments and six spirometry measurements during a 30-year period from 3,140 participants of the Coronary Artery Risk Development in Young Adults (CARDIA) study.
They found stable-heavy smokers (10-20 cigarettes per day) had the greatest drop in FEV1 (–42.2 mL per year) as well as the largest increase in disease risk relative to nonsmokers, including emphysema (OR = 24.1; 95% CI, 12.6-46.2) and obstructive disease (OR = 7.7; 95% CI, 4.1-14.7).
Mathew and colleagues also found that among stable-low-rate smokers (0-5 cigarettes per day) vs. quitters, the quitters had less FEV1 decline vs. stable-low-rate smokers (–33.8 mL/year vs. –35.7 mL/year) and lower odds for emphysema (OR = 2.8, 95% CI 1.2-6.3 vs. OR = 7.7, 95% CI, 4.2-14.2), even though they had greater mean pack-years at year 25. In both groups, the number of years smoking (area-under-the-ROC curve = 0.78) was superior to lifetime pack-years (area-under-the-ROC curve = 0.62) in foretelling the risk for emphysema.
“We were surprised that quitters had a lower disease risk than stable low-rate smokers, although stable low-rate smokers actually had a higher amount of lifetime smoking exposure,” Mathew told Healio Family Medicine. “This underscores the message that it is never too late to quit smoking, and quitting is associated with lung health benefits, even among people who have been heavy smokers.”
“Our main take-home point is that there is no safe threshold of smoking on lung disease risk,” she continued. “Many smokers start by cutting down (reducing the number of cigarettes per day) and this may be a useful strategy in preparing to quit. However, as our findings show, any level of sustained smoking is harmful to lung health, even at a low rate. Our findings are consistent with the message that quitting, and not cutting down, is the most effective method of reducing lung disease risk.”
Mathew suggested a way that primary care physicians can discuss the findings with patients during the interview.
“PCPs should underscore the lung health benefits of quitting at any stage, and the availability of new treatment strategies that may help people who have been unable to quit in the past,” she said. – by Janel Miller
References: Mathew A, et al. Life course cigarette smoking and lung health from young adulthood to middle age: findings from the CARDIA lung study. Presented at: American Thoracic Society 2018 International Conference; May 18-23; San Diego.
Disclosures: Healio Family Medicine was unable to determine relevant financial disclosures prior to publication.