Inhaled medication usage in post-menopausal women and lifetime tobacco smoke exposure: The Women's Health Initiative Observational Study

Objective: While active smoking is a causal agent in respiratory disease, the independent role of secondhand smoke (SHS) merits further investigation. We investigated associations between lifetime active smoking and exposure to secondhand smoke - studied independently - and current use of 1 or more inhaled medications as a surrogate for prevalent pulmonary disease in post-menopausal women.

Study design: Information on lifetime active and passive tobacco exposure and inhaled pulmonary medication usage at enrollment was collected from 88,185 postmenopausal women aged 50-79 enrolled in the Women's Health Initiative Observational Study from 1993 to 1998 at 40 centers in the United States. Participants were recruited from localities surrounding the study centers using a variety of methods, including informational mailings and mass media campaigns.

Main outcome measures: Multivariate adjusted regression models were used to estimate odds ratios and 95% CI according to levels of active smoking and SHS exposure, and trends were tested across categories.

Results: Ever active smokers had an overall OR of 1.97 (95% CI 1.58-2.45) for having one or more prescribed inhaled medication compared with never-smoking women not exposed to active or passive smoke. The overall OR for using inhalers for never-smoking women exposed to any SHS compared with the same reference group was 1.33 (95% CI 1.07-1.65). In a quantified analysis of SHS, never-smoking women with the highest levels of lifetime SHS exposure had an estimated risk of inhaled medication usage of 1.74 (95% CI 1.32-2.30).

Conclusions: The risk of requiring one or more prescribed inhaled medications for pulmonary disease was significantly higher in post-menopausal women who ever smoked or who had lifetime exposure to SHS.