Social determinants of health and life expectancy in US adults.

INTRODUCTION: Individual unfavorable social determinants of health (SDoH) negatively affect health outcomes, yet the combined impact of multiple SDoH on life expectancy is not well understood. METHODS: We analyzed data from a nationally representative sample of US adults aged ≥18 years in NHANES (1999–2018) to examine associations between unfavorable SDoH—both individually and in combination—and life expectancy. RESULTS: Among 45,516 participants (mean age 47.7 years; 51.4% women) with a median follow-up of 9.4 years, 6,164 deaths occurred. Four key SDoH—employment, family income, education, and marital status—were individually associated with shorter life expectancy at age 50: unemployment (−4.2 years, 95% CI 3.9–4.6), low income (−3.5, 3.1–3.9), low education (−3.1, 2.7–3.4), and unmarried status (−2.4, 2.1–2.8). Among 16 combined SDoH profiles, participants who were unemployed, low-educated, and unmarried lost 10.8 years compared with the most favorable profile. Notably, education had the largest individual impact, but its effect diminished when combined with other adverse SDoH; well-educated individuals with multiple unfavorable SDoH lost more life years than less-educated counterparts (7.2 vs. 4.9 years). CONCLUSIONS: In this nationally representative cohort, four key SDoH strongly influenced life expectancy. Multiple adverse SDoH had additive effects, and the impact of education was context-dependent, emphasizing the importance of considering combined social risk in public health strategies.