Joint effects of depression and social determinants of health on mortality risk among US adults: a cohort study

BackgroundUnfavorable social determinants of health (SDoH) are associated with depression. Both depression and SDoH are associated with increased risks of mortality, but their joint impacts on mortality risks remain unclear. This study aims to investigate the joint effects of depression and SDoH on mortality risk.MethodsUtilizing data from the National Health and Nutrition Examination Survey (NHANES) 2007-2018, 24,727 adults aged >= 20 were included. SDoH was assessed based on the 5 domains outlined in the U.S. Healthy People 2030 initiative. The cumulative number of unfavorable SDoH was calculated and categorized into low and high burden levels. The definition of depression was based on the Patient Health Questionnaire-9 (PHQ-9) scores >= 10. The joint associations of depression and SDoH with all-cause, cardiovascular disease (CVD), and cancer mortality were examined using Cox proportional hazard models.ResultsWe identified 2,377 (6.84%) all-cause deaths (CVD, 717; cancer, 606) during a median follow-up of 7.0 years. Depression was associated with increased mortality risks, and SDoH could explain 32.4% and 28.3% of the associations between depression and all-cause and CVD mortality, respectively. No significant interactions were observed between depression and SDoH on mortality. However, a low burden of unfavorable SDoH reduced the risk of all-cause mortality in depressed patients (hazard ratio [HR], 0.58; 95% confidence interval [CI]: 0.36-0.92). In the joint analysis, individuals with both depression and a high burden of unfavorable SDoH had the highest risks of all-cause and CVD mortality. Specifically, compared with individuals with no depression and a low burden of unfavorable SDoH, those with depression and a high burden of unfavorable SDoH had higher risks of all-cause (HR, 2.52; 95% CI: 2.01-3.18) and CVD mortality (HR, 2.79; 95% CI: 1.95-3.99).ConclusionAdults with both depression and a high burden of unfavorable SDoH had the highest risks of all-cause mortality and CVD mortality. The result suggests considering depression and SDoH jointly in developing targeted intervention strategies to improve survival outcomes and calls for larger cohort studies and clinical trials to validate our findings.