Dietary inflammatory index is associated with female infertility: a cross-sectional analysis of the Fasa adults cohort study.

Abstract

Background: Infertility is a major public health concern with substantial biological, psychological, and social consequences for women. Accumulating evidence suggests that chronic low-grade inflammation may contribute to female reproductive dysfunction. Diet is an important modifiable determinant of systemic inflammation, and the Dietary Inflammatory Index (DII) has been developed to quantify the inflammatory potential of habitual dietary intake. However, evidence regarding the association between DII and female infertility remains limited, particularly in Middle Eastern populations. This study aimed to examine the association between DII and self-reported female infertility among women participating in the Fasa Adults Cohort Study, Iran.

Methods: This cross-sectional analysis included 2,036 women aged 35-45 years. Dietary intake was assessed using a validated 118-item food frequency questionnaire, and DII scores were calculated from 31 available dietary components. Infertility was defined as self-reported inability to conceive after at least 12 months of regular unprotected sexual intercourse. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for infertility according to DII, after adjustment for demographic, anthropometric, and lifestyle covariates.

Results: Among the study participants, 595 women (29.2%) reported a history of infertility. Mean DII score was significantly higher among women with infertility than among fertile women. In the crude model, DII was not significantly associated with infertility. However, after multivariable adjustment, each one-unit increase in DII was associated with higher odds of infertility (adjusted OR = 1.29; 95% CI: 1.13-1.63). This association remained after adjustment for BMI, smoking status, age, educational level, waist circumference, and total energy intake.

Conclusion: Higher DII scores were independently associated with greater odds of self-reported infertility in this Iranian cohort. These findings suggest that the inflammatory potential of diet may be related to female reproductive health. However, because of the cross-sectional design, causality and temporality cannot be inferred, and further prospective and mechanistic studies are warranted.