Childhood cigarette smoking heightens COPD risk in adulthood

Key takeaways:

• COPD prevalence was higher among adults who started smoking during childhood vs. at age 15 years or later.
• Childhood smoking was linked to an increased risk for COPD in adults aged 40 years or older.

In adulthood, the risk for COPD rose with regular cigarette smoking starting before age 15 years, according to results published in American Journal of Respiratory and Critical Care Medicine.

“In this sample, the developmental window for increased risk due to childhood smoking ended at about age 20 years, which coincides with the time [FEV₁] reaches its peak during adolescence,” James D. Sargent, MD, Scott M. and Lisa G. Stuart Professor, as well as professor of pediatrics, professor of biomedical data science and professor of community and family medicine at Dartmouth Geisel School of Medicine, and colleagues wrote.

Using data from the 2020 National Health Interview Survey, Sargent and colleagues assessed 22,374 adults (52.8% women; 75% white) aged 40 years or older to determine how COPD risk is linked to the age of smoking initiation (< 15 years old vs. ≥ 15 years old).

Researchers used multivariable analysis that accounted for current smoking, cigarette pack-years and covariates to find this relationship.

Over half of the total cohort never smoked (60%), and researchers observed more former smokers than current smokers (28% vs. 13%).

Within the study population, 7.1% of adults self-reported a COPD diagnosis, and this diagnosis was reported more frequently in the cohort who started smoking regularly before age 15 years vs. the cohort who started smoking regularly at age 15 years or older and the cohort who never smoked (23.1% vs. 11.6% vs. 2.6%).

Compared with the cohort of regular smokers at age 15 years or older, researchers found more median pack-years in the cohort of regular smokers before age 15 years (29 vs. 15).

In terms of smoking intensity, the median number of cigarettes per day was 20 for those reporting early-onset/childhood smoking, whereas this number was smaller for those reporting later-onset smoking (10 cigarettes per day).

Between these two sets of adults, researchers found that childhood cigarette smoking raised the risk for COPD (adjusted RR = 1.41; 95% CI, 1.22-1.63).

Based on smoking status, the risk for COPD was elevated among current smokers vs. former and never smokers (aRR = 1.18 for each 10 additional pack-years).

Among those reporting current smoking, researchers divided the cohort based on smoking intensity (light, < 10 cigarettes per day; medium, 11-19 cigarettes per day; heavy, ≥ 20 cigarettes per day) and observed a significant elevated risk for COPD among childhood smokers reporting medium intensity (< 15 years, aRR = 6; 95% CI, 4.4-8.17 vs. ≥ 15 years, aRR = 4.09; 95% CI, 3.18-5.26) or heavy intensity (< 15 years, aRR = 4.03; 95% CI, 2.95-5.5 vs. ≥ 15 years old, aRR = 2.59; 95% CI, 2-3.36).

Notably, the link between childhood smoking and COPD risk was unchanged after using pack-years instead of smoking duration in sensitivity analysis. In contrast, this switch meant current smoking was no longer related to COPD risk, according to researchers.

In terms of smoking duration, the longer the amount of time smoking, the greater the risk for COPD (RR = 1.39; 95% CI, 1.32-1.46 for each 10 additional years of smoking).

As a final measure, researchers evaluated the risk for COPD among those who started smoking between the ages of 15 and 19 years and observed an increased risk vs. those who started at age 20 years or later (RR = 1.27; 95% CI, 1.05-1.53). This risk was slightly lower than the elevated risk found for those who started smoking before age 15 years vs. at age 20 years or later (RR = 1.7; 95% CI, 1.37-2.11).

“Although it would be worthwhile to replicate the findings in other studies of COPD, this study gives child health providers and public health officials reason to be very concerned about future chronic disease among patients who begin smoking during early adolescence, both because of the increased risk of nicotine addiction and perhaps because of its impact on lung development,” Sargent and colleagues wrote.