Intersections of Social Determinants, Food Insecurity, Diet Quality, and Mental Health in Mortality Risk: Joint and Mediating Effects

Background: Poor nutrition is a major contributor to disease and mortality, and intersects with food insecurity, broader social determinants of health (SDOH), and mental health. However, few studies have examined how these factors jointly shape mortality risk or mediate each other. Objective: To evaluate independent and mediating relationships among diet quality, food insecurity, SDOH, and mental health in relation to mortality among U.S. adults. Methods: Ten cycles of the National Health and Nutrition Examination Survey (1999–2018) were linked to the National Death Index. Diet quality was assessed using the Alternative Healthy Eating Index–2010 (AHEI-2010). Food insecurity was defined from the U.S. Household Food Security Survey Module. SDOH were summarized in a composite score (range: 0-8), including income, education, employment, insurance, SNAP participation, marital status, and homeownership. Mental health was represented using depressive symptoms and sleep indicators, each evaluated separately as sensitivity analyses. Demographic-adjusted Cox models evaluated the independent associations of diet quality, food insecurity, SDOH, and mental health with all-cause mortality, and their mediating effects. Additional analyses examined the extent to which prevalent cardiometabolic conditions mediated the diet–mortality association. Results: In multivariable models, each higher SDOH unit was associated with 14% higher mortality. Food insecurity mediated 20% of this association; diet quality, 12%; and depressive symptoms, 5%. Adjusting for SDOH, food insecurity was associated with 77% higher mortality, mediated by diet quality (1%) and depressive symptoms (7%). Evaluating all factors jointly, each higher SDOH unit was associated with 19% higher mortality; each 10 units of AHEI-2010, 9% lower; food insecurity, 79% higher; depressive symptoms, 36% higher; and sleep trouble, 34% higher. Conclusions: Diet-related metrics mediate a relatively small proportion of mortality risk related to SDOH but are themselves independently associated with mortality. Diet quality and depressive symptoms are not major downstream mediators of the food insecurity-mortality relationship but rather reflect independent risks. These new findings suggest a need to address each of these important risks to poor health, without assuming that policies to address one will address the others.