Association of allostatic load and dietary inflammatory index with depressive symptoms among U.S. adults: NHANES 2007-2018.

Abstract

Background: Both chronic stress and pro-inflammatory diets have been independently linked to depressive symptoms (DSs). However, their joint effects are uncertain.

Methods: This study included 20,446 U.S. adults from the National Health and Nutrition Examination Survey (NHANES) 2007-2018. Chronic stress was quantified using allostatic load score (ALS) derived from eight biomarkers. Dietary inflammatory potential was quantified using Dietary Inflammation Index (DII) calculated from two 24-h dietary recalls. DSs were assessed using the Patient Health Questionnaire-9 (PHQ-9). Weighted logistic regression, restricted cubic splines (RCS), mediation, and population attributable fraction (PAF) analyses were conducted.

Results: Both ALS (adjusted odds ratio [aOR] = 1.23, 95 % confidence interval [CI]: 1.16-1.29) and DII (aOR = 1.21, 95%CI:1.15-1.26) independently and synergistically increased DSs risk, showing significant linear trends (both P-overall<0.001) with no evidence of nonlinearity. The highest-risk group (highest ALS quartile + pro-inflammatory diet) exhibited a 3.94-fold increased risk (aOR = 4.94, 95 % CI: 2.73-8.94) compared to the reference group. DII partially mediated the ALS-DSs association (mediation proportion: 4.27 %, 95 % CI: 2.96 %-6.00 %). Eliminating high ALS and pro-inflammatory diets could prevent 40.4 % (95 % CI: 31.7-49.2 %) of depression cases.

Limitations: The cross-sectional design limits causal inference, and residual confounding may exist due to unmeasured factors.

Conclusions: This study highlights the independent, synergistic, and mediated effects of ALS and DII on DSs. Integrated interventions addressing both stress and diet may help mitigate depression burden in U.S. adult.