Association between antioxidants and pelvic inflammatory disease: a nationwide survey and mendelian randomisation study

The relationship between dietary antioxidants and pelvic inflammatory disease (PID) remains poorly understood. This study aimed to investigate this association in US women using both observational data and Mendelian randomisation (MR) to assess causality.

We conducted a cross-sectional analysis of 4,003 women aged ≥20 from the National Health and Nutrition Examination Survey (2013-2018). The Composite Dietary Antioxidant Index (CDAI) was calculated from six dietary antioxidants. PID was self-reported. Multivariable logistic regression was used to assess the association between the CDAI and PID, with subgroup analyses to test robustness. Subsequently, a two-sample MR analysis using the inverse-variance weighted (IVW) method was performed to evaluate a potential causal link.

The prevalence of PID was 5.6% (224/4,003). In the fully adjusted logistic regression model, a higher CDAI was associated with lower odds of PID (Odds Ratio [OR] 0.95, 95% Confidence Interval [CI] 0.92-0.99). Among individual components, higher zinc intake was also inversely associated with PID (OR 0.96, 95% CI 0.93-0.99, P = 0.037). The inverse association between the CDAI and PID was consistent across all subgroups. However, the MR analysis did not find a significant causal relationship between antioxidant levels and PID risk.

A higher dietary antioxidant intake, as measured by the CDAI, is associated with a lower prevalence of PID in US women. However, our MR findings do not support a causal role for individual antioxidants in the development of PID. Further longitudinal studies are warranted to enhance our understanding of the interactions between antioxidants and PID.