TY - JOUR T1 - Lung function decline in former smokers and low-intensity current smokers: a secondary data analysis of the NHLBI Pooled Cohorts Study. JF - Lancet Respir Med Y1 - 2020 A1 - Oelsner, Elizabeth C A1 - Balte, Pallavi P A1 - Bhatt, Surya P A1 - Cassano, Patricia A A1 - Couper, David A1 - Folsom, Aaron R A1 - Freedman, Neal D A1 - Jacobs, David R A1 - Kalhan, Ravi A1 - Mathew, Amanda R A1 - Kronmal, Richard A A1 - Loehr, Laura R A1 - London, Stephanie J A1 - Newman, Anne B A1 - O'Connor, George T A1 - Schwartz, Joseph E A1 - Smith, Lewis J A1 - White, Wendy B A1 - Yende, Sachin KW - Adult KW - Aged KW - Case-Control Studies KW - Ex-Smokers KW - Female KW - Follow-Up Studies KW - Humans KW - Lung KW - Male KW - Middle Aged KW - National Heart, Lung, and Blood Institute (U.S.) KW - Non-Smokers KW - Respiratory Physiological Phenomena KW - Smokers KW - Smoking KW - Spirometry KW - United States KW - Young Adult AB -

BACKGROUND: Former smokers now outnumber current smokers in many developed countries, and current smokers are smoking fewer cigarettes per day. Some data suggest that lung function decline normalises with smoking cessation; however, mechanistic studies suggest that lung function decline could continue. We hypothesised that former smokers and low-intensity current smokers have accelerated lung function decline compared with never-smokers, including among those without prevalent lung disease.

METHODS: We used data on six US population-based cohorts included in the NHLBI Pooled Cohort Study. We restricted the sample to participants with valid spirometry at two or more exams. Two cohorts recruited younger adults (≥17 years), two recruited middle-aged and older adults (≥45 years), and two recruited only elderly adults (≥65 years) with examinations done between 1983 and 2014. FEV decline in sustained former smokers and current smokers was compared to that of never-smokers by use of mixed models adjusted for sociodemographic and anthropometric factors. Differential FEV decline was also evaluated according to duration of smoking cessation and cumulative (number of pack-years) and current (number of cigarettes per day) cigarette consumption.

FINDINGS: 25 352 participants (ages 17-93 years) completed 70 228 valid spirometry exams. Over a median follow-up of 7 years (IQR 3-20), FEV decline at the median age (57 years) was 31·01 mL per year (95% CI 30·66-31·37) in sustained never-smokers, 34·97 mL per year (34·36-35·57) in former smokers, and 39·92 mL per year (38·92-40·92) in current smokers. With adjustment, former smokers showed an accelerated FEV decline of 1·82 mL per year (95% CI 1·24-2·40) compared to never-smokers, which was approximately 20% of the effect estimate for current smokers (9·21 mL per year; 95% CI 8·35-10·08). Compared to never-smokers, accelerated FEV decline was observed in former smokers for decades after smoking cessation and in current smokers with low cumulative cigarette consumption (<10 pack-years). With respect to current cigarette consumption, the effect estimate for FEV decline in current smokers consuming less than five cigarettes per day (7·65 mL per year; 95% CI 6·21-9·09) was 68% of that in current smokers consuming 30 or more cigarettes per day (11·24 mL per year; 9·86-12·62), and around five times greater than in former smokers (1·57 mL per year; 1·00-2·14). Among participants without prevalent lung disease, associations were attenuated but were consistent with the main results.

INTERPRETATION: Former smokers and low-intensity current smokers have accelerated lung function decline compared with never-smokers. These results suggest that all levels of smoking exposure are likely to be associated with lasting and progressive lung damage.

FUNDING: National Institutes of Health, National Heart Lung and Blood Institute, and US Environmental Protection Agency.

VL - 8 IS - 1 ER -