Women who said they were exposed to environmental tobacco smoke as children were nearly twice as likely to have COPD as those who were not exposed (OR 1.9, 95% CI 1.0 to 3.7), according to Ane Johannessen, PhD, of Haukeland University Hospital in Bergen, Norway, and colleagues.
The relationship did not reach statistical significance among men, although early-life exposure to smoke was associated with greater odds of certain COPD-related symptoms, including morning cough, cough with phlegm, and chronic cough (ORs 1.6 to 1.7), the researchers reported online in Respirology.
“Although active smoking is still the most important risk factor for COPD, reduction of childhood environmental tobacco smoke exposure could contribute to the prevention of COPD and respiratory symptoms,” they concluded.
Johannessen and colleagues looked at data from the Bergen COPD Cohort Study, which was conducted from 2006 to 2009. The analysis included 433 patients with COPD and 325 controls ages 40 to 79. All underwent spirometry and completed questionnaires about respiratory symptoms and risk factors for COPD.
The patients with COPD had a smoking history of more than 10 pack-years.
Overall, 61% of the patients and controls reported being exposed to environmental tobacco smoke for at least one year of their childhood.
After adjustment for several variables, including age, smoking status, and pack-years smoked, smoke exposure in childhood was associated with a higher likelihood of having COPD among women, but not men.
Other predictors of COPD among the women included occupational dust or gas exposure, a family history of COPD, and lower educational achievement (ORs 1.9 to 3.7). In addition, family history was associated with all of the respiratory symptoms, current exposure to tobacco smoke in the home was associated with morning cough, and lower educational achievement was associated with dyspnea (ORs 1.7 to 3.0).
Among the men, the risk factors for COPD included occupational dust or gas exposure, family history and level of education (ORs 2.2 to 3.6). Dyspnea was predicted by occupational dust or gas exposure and family history (ORs 2.2 and 2.4, respectively).
“In the present analyses, both the magnitude and precision of the risk estimates were modest,” the authors wrote. “However, this is to be expected for a risk factor study of a complex chronic disease such as COPD, particularly when looking at childhood exposures and a long latency of effect.”
One other study — the Chinese Guangzhou Biobank Cohort Study — has examined the association between childhood smoke exposure and COPD risk in adults; it did not find a relationship between the two.
Johannessen and colleagues said the discrepancy could be the result of differences between the study populations. In the Chinese study, 88% of the participants were female. According to the World Health Organization, only 4% of Chinese women smoke.
In contrast, 43% of the participants in the Norwegian study were female. The prevalence of smoking among men and women in that country is 19%.
In addition, the Chinese study was comprised of people who had never smoked, whereas only 6% of the participants in the Norwegian study had never smoked.