Depressive symptoms, social support, and risk of adult asthma in a population-based cohort study.

OBJECTIVE: To investigate the association between depressive symptoms, social support, and prevalent as well as incident asthma. Depressive symptoms and social support may affect the development of asthma. This relationship could be mediated by health behaviors and/or inflammatory processes. Evidence from prospective cohort studies on depressive symptoms and social support in relation to asthma risk in adults remains sparse.
METHODS: Between 1992 and 1995, a population-based sample of 5114 middle-aged adults completed questionnaires covering depressive symptoms, social support, self-reported asthma, and potential confounders. Among those alive in 2002/2003, 4010 (83%) were followed-up by questionnaires. Associations with prevalent and incident asthma were estimated by prevalence ratios (PR) and risk ratios (RR) along with corresponding 95% confidence intervals (CIs), using Poisson regression. PRs and RRs were adjusted for demographics, family history of asthma, smoking, alcohol consumption, body mass index, and physical exercise.
RESULTS: Cross-sectional analyses indicated that the prevalence of asthma was positively associated with depressive symptoms and inversely related to social support. Prospective analysis suggested a 24% increased risk of asthma with each 1-standard deviation increase in depressive symptoms (RR, 1.24; 95% CI, 1.02, 1.50), whereas the social support z score showed an inverse association with asthma incidence (RR, 0.71; 95% CI, 0.58, 0.88). Analyses with tertiles suggested similar, but nonsignificant, associations. Omitting health-related life-style variables from the multivariable models did not substantially alter these associations.
CONCLUSIONS: Risk of adult asthma was found to increase with depressive symptoms and to decrease with social support. These associations do not seem to be explained by health-related life-style factors.