Abstract
BACKGROUND: All-cause mortality risk and dementia occurrence have been previously hypothesized to be linked with food insecurity and poor dietary quality. OBJECTIVE: The aims of the study were to test mediation and interactions between food insecurity, diet quality, and dementia status in relation to all-cause mortality. DESIGN: The interplay of food insecurity, diet quality, and dementia in their associations with all-cause mortality was studied, in terms of interactions and mediating effects, using secondary longitudinal data from a sample of older US adults from the Health and Retirement Study (HRS, 2012-2020). Reduced (age, sex, race/ethnicity-adjusted, M1) and fully adjusted (sociodemographic, lifestyle, and health-related factor-adjusted, M2) models were tested, and stratification by sex and race/ethnicity was carried out. PARTICIPANTS/SETTING: US older adults (n = 2894; 2012-2014, mean baseline age of 76.4 y) were selected from this national longitudinal sample. MAIN OUTCOME MEASURES: The outcome of interest was all-cause mortality risk for follow-up until the end of 2020. STATISTICAL ANALYSES PERFORMED: Cox proportional hazards, four-way decomposition, and generalized structural equations models (GSEM) were used. RESULTS: Overall, 902 deaths occurred (51 per 1000 person-years). Food insecurity (yes vs no) was not associated with mortality risk in M1, although inversely related to this outcome in M2 (Cox models and GSEM). Food insecurity was directly related to Ln(dementia odds) in M1 only (β ± standard error [SE]: 0.23 ± 0.05, P < .001, GSEM). Diet quality as measured by HEI-2015 (z-scored), although inversely related to food insecurity in reduced GSEM (β ± SE: -0.18 ± 0.06, P = .005), was also inversely related to both Ln(dementia odds), z-scored (β ± SE: -0.14 ± 0.03l P < .001) and mortality risk (LnHR ± SE: -0.14 ± 0.03; P < .001, M1). Ln(dementia odds) was strongly associated with mortality risk (HR = 1.39; 95% CI, 1.31-1.48; P < .001, M2). In both four-way decomposition models and GSEM, the total effect of diet quality on mortality risk was partially mediated through Ln(dementia odds) (M1 and M2), explaining 15%-21% of this total effect. CONCLUSION: Diet quality-mortality risk association was partially mediated through dementia, with inconsistent findings observed for food insecurity.