Abstract
BACKGROUND: Physical functioning indexed multimorbidity is strongly associated with long-term mortality, but its role in poor mental health has not been quantified. METHODS: A total of 252 002 community-dwelling adults in the Nurses' Health Study (NHS), NHS II, and Health Professionals Follow-up Study (HPFS) prospective cohorts reported physician-diagnosed diseases and the Short Form-36 over 8 years and had 24-year follow-up for suicide mortality. We quantified multimorbidity using a multimorbidity-weighted index (MWI). We used multivariable-adjusted proportional hazards models with competing risks for suicide mortality and mixed-effects models to estimate mental health-related quality of life (HRQOL). RESULTS: Multimorbidity was associated with an increased risk of suicide mortality in an approximately linear manner, with roughly two- to threefold higher risk in adults with the highest vs lowest quartile MWI in adjusted models: NHS hazard ratio (HR) = 3.01 (95% confidence interval [CI] = 1.48-6.11); NHS II HR = 3.04 (95% CI = 1.82-5.09); HPFS HR = 1.74 (95% CI = 1.08-2.81). Greater MWI was associated with worse mental HRQOL 8 years later across all scales and the mental component summary (MCS) in a dose-response manner. This association was attenuated but persisted after adjustment for baseline mental HRQOL and other covariates. Adults with the highest quartile MWI had lower MCS in adjusted models compared with those with the lowest quartile MWI: NHS ß = -0.61 (95% CI = -0.78 to -0.44); NHS II ß = -1.25 (95% CI = -1.44 to -1.06). CONCLUSION: Multimorbidity is associated with substantially higher suicide mortality risk and worse mental HRQOL across all available scales, even when indexed to physical functioning. These results highlight the substantial mental health burden imposed by multimorbidity at all ages and sexes. J Am Geriatr Soc 67:511-519, 2019.