Social determinants of health and age-related differences in all-cause mortality: evidence from National Health and Nutrition Examination Survey

Unfavorable social determinants of health (SDoH) are linked to higher risks of poor health, but evidence on their age-specific distribution and association with all-cause mortality are limited. We analyzed NHANES data (2003–2018) from 14,604 participants, stratified by age and cumulative unfavorable SDoH. The association between SDoH and all-cause mortality was assessed using Kaplan–Meier curves, Cox regression models, and restricted cubic spline (RCS) analysis. Among 14,604 participants, 1,835 deaths (8.78%) were recorded. Kaplan–Meier curve analysis showed lower survival rates in the middle and high SDoH groups compared to the low SDoH group. RCS analysis showed a nonlinear relationship between SDoH and all-cause mortality. Cox regression analysis revealed that higher SDoH scores were significantly associated with increased all-cause mortality across all age groups. After full adjustment, each unit increase in SDoH score was linked to a 21% higher mortality risk in young group, 28% in middle-aged group, and 13% in the elderly. Compared to those with low SDoH, individuals in the high SDoH group had the greatest mortality risk in the middle-aged group (HR: 3.10). Distinct SDoH patterns emerged across ages: employment status, food security, and health insurance status were key in young group; middle-aged group were affected by a broader range of SDoH components, while the elderly showed weaker but still significant associations. SDoH characteristics differ across age groups, and unfavorable SDoH are strongly associated with higher all-cause mortality, with age-specific variations. Targeted interventions are needed to address each age group’s unique health needs.