Association between depression and mortality in persons with asthma: a population-based cohort study

Background The relation between depression and mortality in patients with asthma is not well known. This study aimed to assess the impact of depression on mortality in asthmatic patients in US adults. Methods This observational study used data from the 2005 to 2014 National Health and Nutrition Examination Survey (NHANES). Depression was measured using the Patient Health Questionnaire-9 (PHQ-9). We used survey-weight adjusted Cox proportional hazard models to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for the association between depression and all-cause mortality. Results A total of 1865 participants with asthma were included in this study. Among them, 264 (14.16%) had depressive symptoms. During 9970 person-years of follow-up, there were 24 (9.1%) deaths in 264 patients with depression compared with 100 (6.3%) deaths in 1601 patients without depression. For unadjusted analyses, depression was associated with an increased risk of all-cause mortality (HR, 2.22 [95% CI 1.32-3.73]). This association was persistent after adjustment for age, sex, race/ethnicity, and body mass index (HR, 2.71 [95% CI 1.58-4.66]). However, we did not observe a significant association between depression and mortality after controlling for extensive co-morbidities (HR, 1.92 [95% CI 0.82-4.45]). Subgroup analyses further revealed that depression was an independent risk factor for mortality only in the females (HR, 3.78 [95% CI 1.17, 12.26]) but not all asthmatic patients. Conclusions The present study suggested that depressive disorder was common in asthmatic patients and depression in asthmatic patients was associated with a higher mortality rate. Depression was an independent risk factor for mortality in female patients.