Association between dietary inflammatory index and polycystic ovary syndrome: a meta-analysis of case-control studies.

This study aimed to systematically analyze the association of the dietary inflammatory index (DII) with polycystic ovary syndrome (PCOS) status, thus offering evidence-based support for dietary interventions in the management of PCOS. Four databases were systematically searched to collect case-control studies on DII and PCOS published up to December 21, 2025. The Newcastle-Ottawa Scale (NOS) was utilized to assess the risk of bias in the included studies. Using Stata 15.0, we conducted a meta-analysis to compare DII scores in PCOS patients versus those in healthy controls. Subgroup analyses were conducted to identify sources of heterogeneity. An exploratory meta-regression was conducted, but due to the small number of studies, the results could not be interpreted. Six case-control studies involving 1,554 participants were ultimately included. Meta-analysis revealed slightly but statistically significantly higher DII scores in the PCOS group than in healthy controls (standardized mean difference [SMD]: 0.23; 95% confidence interval [CI]: 0.06-0.40; P = 0.008). Sensitivity analyses suggested robustness of the results. Egger's test showed no statistical evidence of publication bias (P = 0.611); however, with only six studies the statistical power was very low, so publication bias cannot be excluded, and this analysis should be regarded as exploratory. Pro-inflammatory dietary patterns are modestly associated with PCOS. Although causality inference is impossible due to the design of included studies, existing evidence supports DII as a potential tool for estimating PCOS status associated with diet. The small effect size observed in this study indicates a significant association between DII and PCOS. However, statistical association does not necessarily imply practical clinical relevance, and further studies are warranted to replicate and validate this relationship. https://www.crd.york.ac.uk/PROSPERO/view/1239576, identifier CRD420251239576.