Income Inequality, Gender Disparities, and Ethnic Differences: Investigating Allostatic Load in American Adults

To estimate the association between income inequality and allostatic load score (AL) in adults ages 20 years and older, with a particular focus on the differential impacts across racial and gender groups. By examining this association, the study seeks to inform targeted policy interventions to mitigate health disparities exacerbated by economic inequality.

Utilizing data from the 1999-2016 National Health and Nutrition Examination Survey (NHANES), we assessed AL through eight biomarkers: systolic blood pressure (mm Hg), diastolic blood pressure (mm Hg), pulse rate (beats/min), body mass index (kg/m²), glycohemoglobin (%), direct HDL cholesterol (mg/dL), total cholesterol (mg/dL), and serum albumin (g/dL). Employing negative binomial regression (NBRG), we estimated incidence rate ratios (IRR) for a sample comprising 7367 men and 7814 women, adjusting for age, race/ethnicity, marital status, education, health insurance, comorbidity, and mental health professional utilization. Gini coefficients (GC) were calculated to assess income inequality among men and women.

Findings revealed that men exhibited a higher poverty-to-income ratio (PIR) compared to women (3.12 vs. 2.86, p < 0.01). Yet, women experienced higher rates of elevated AL (AL > 4) (31.8% vs. 29.0%) and were more adversely affected by income inequality (GC: 0.280 vs. 0.333). NBRG results indicated that high PIR individuals had a lower IRR (0.96; CI:0.92-0.95) compared to their low PIR counterparts, a trend observed in women but not men. High PIR was notably protective among White non-Hispanic (WNH) men and women. Additionally, vigorous and moderate physical activity engagement was associated with lower AL (IRR: 0.89, CI: 0.85-0.93).

The study emphasizes the importance of implementing policies that target AL in low-income populations across all racial groups, with a specific focus on Black non-Hispanic (BNH) and Hispanic communities. By prioritizing these groups, policies can more effectively target the nexus of income inequality, health disparities, and allostatic load, contributing to the reduction of health inequities.