Asthma and smoking status in a population-based study of California adults

Objective. Because they experience respiratory symptoms, adults with asthma might be expected to avoid cigarette smoking. However, previous studies have not adequately addressed whether adults with asthma have a lower prevalence of smoking than the general population. The authors sought to determine whether adult asthmatics are less likely to smoke cigarettes than members of the general population. Methods. The authors used data from a random sample of 2,902 California adults ages 18 years or older, with oversampling of African Americans, Asian/Pacific Islanders, adults with disabilities, and adults aged 45 to 70 years. Sampling weights were used in all analyses. In this cross-sectional study, 217 participants (7.5%) reported a physician diagnosis of asthma. Results. The prevalence of "ever smoking" was similar among adults with asthma (48.3%) and those without asthma (43.0%) (risk difference 5.3%; 95% Cl -1.6%, 12.2%). There was also no difference in the prevalence of "current smoking" among adults with asthma (20.2%) compared with the non-asthmatic subjects (18.8%) (risk difference 1.4%; 95% Cl -4.2%, 6.9%). After controlling for age, gender, race, and education, there was no evidence that adults with asthma were less likely to ever smoke. Although the confidence intervals did not exclude "no association," asthma was actually associated with an increased risk of ever smoking (OR 1.3; 95% Cl 1.0, 1.8). There was also no association between asthma and the risk of current smoking after controlling for covariates (OR 1.1; 95% CI 0.8, 1.6). Moreover, there were no differences in "age of smoking initiation," "duration of smoking," or "intensity of smoking" after adjusting for demographic characteristics. Redefining the referent group to exclude respondents with other chronic lung diseases did not appreciably change study conclusions. Conclusion. Adults with asthma do not appear to selectively avoid cigarette smoking, Specific smoking prevention and cessation efforts should be targeted to adults with asthma.