Analysis Reveals Smoking Cessation’s Impact on Lung Function
Former smokers and low-intensity current smokers have accelerated lung function decline compared with individuals who have never smoked, according to a new analysis of the National Heart, Lung, and Blood Institute (NHLBI) Pooled Cohorts Study.
“These results suggest that all levels of smoking exposure are likely to be associated with lasting and progressive lung damage,” the researchers wrote.
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The study authors used data on 6 US population-based cohorts from the NHLBI Pooled Cohort Study to reach this conclusion. Patients who had had valid spirometry at 2 or more examinations between 1983 and 2014 were included in the analysis. In all, data on 25,352 participants aged 17 to 93 years who had completed 70,228 valid spirometry examinations were analyzed.
After adjusting for sociodemographic and anthropometric factors, forced expiratory volume in one second (FEV1) decline among former smokers, current smokers, and never smokers were compared. Based on the duration of smoking cessation as well as on the cumulative (number of pack-years) and current (number of cigarettes per day) cigarette consumption, differential FEV1 decline was also assessed.
Over a median follow-up of 7 years—and at the median age of 57 years—sustained never smokers had FEV1 decline of 31.01 mL per year. Meanwhile, FEV1 decline was 34.97 mL per year among former smokers and 39.92 mL per year among current smokers.
After adjustments, former smokers had an accelerated FEV1 decline of 1.82 mL per year compared with never smokers. According to the study authors, this was approximately 20% of the effect estimate for current smokers.
Compared with never smokers, former smokers experienced accelerated FEV1 decline for decades after smoking cessation. Current smokers with low cumulative cigarette consumption (<10 pack-years) also experienced accelerated FEV1 decline compared with never smokers.
Current smokers who reported having fewer than 5 cigarettes per day had an effect estimate for FEV1 decline that was 68% of that among current smokers consuming 30 or more cigarettes per day (7.65 mL per year vs 11.24 mL per year). Additionally, the effect estimate for FEV1 decline was 5 times greater among low-intensity current smokers who had fewer than 5 cigarettes than among former smokers (1.57 mL per year).
“Among participants without prevalent lung disease, associations were attenuated but were consistent with the main results,” according to the researchers.
Oelsner EC, Balte PP, Bhatt SP, et al. Lung function decline in former smokers and low-intensity current smokers: a secondary data analysis of the NHLBI Pooled Cohorts Study. Lancet Respir Med. 2020;8(1):34-44. https://doi.org/10.1016/S2213-2600(19)30276-0.