Association of life satisfaction with disability-free survival: role of chronic diseases and healthy lifestyle

Abstract

Background: this article investigates the association between life satisfaction and disability-free survival, and explores the roles of chronic diseases and healthy lifestyle in this association.

Method: a cohort of 2,116 functionally independent adults aged ≥60 was followed up to 12 years. At baseline, life satisfaction was assessed with the Life Satisfaction Index A (LSI-A). Disability-free survival was defined as the survival till the first occurrence of either death, dementia or physical disability. Information on lifestyle factors was collected via questionnaire. Chronic diseases were ascertained through clinical examinations at baseline and each follow-up. Data were analysed using Cox proportional hazard regression models and Laplace regression.

Results: over follow-up, 1,121 participants died, developed dementia, or became disabled. High LSI-A versus Low LSI-A had a lower risk of death, dementia and physical disability (hazard ratio [HR] 0.79, 95% confidence intervals [CI] 0.67-0.94), and had a longer disability-free period by 1.73 (95% CI 0.18-3.32) years. In mediation analysis, accumulation of chronic diseases mediated 17.8% of the association between LSI-A and disability-free survival. In joint effect analysis, participants with high LSI-A and a favourable lifestyle profile had a HR of 0.53 (95% CI 0.41-0.69) for the composite endpoint, and lived 3.2 (95% CI 1.35-5.11) disability-free years longer than those with low life satisfaction and an unfavourable lifestyle profile.

Discussion: high life satisfaction is independently associated with longer disability-free survival. This association is partially mediated by a lower burden of chronic diseases and is reinforced by healthy lifestyle.

Keywords: Laplace regression; chronic diseases mediation; disability-free survival; healthy lifestyle; life satisfaction; older people.