BackgroundAlthough adherence to a healthy dietary pattern is one of the primary recommendations for the prevention of polycystic ovary syndrome (PCOS), there is still no conclusive evidence of which specific dietary pattern is best. The Lifelines diet score (LLDS) is a new, evidence-based scoring system to determine diet quality, and its association with PCOS has not been investigated. The present study aimed to assess the association between LLDS and PCOS in Iranian women.Materials and methodsThis frequency-matched case-control study was carried out on 108 women with PCOS and 108 women without PCOS as a control group in Yazd, Iran. Healthy controls were matched to PCOS women based on age and BMI. The validated 178-item food frequency questionnaire was used to assess the usual dietary intake. Logistic regression was used to estimate the association between LLDS and PCOS.ResultsThe findings of the present study showed women in the highest tertile of LLDS compared with the participants in the lowest tertile had 90% lower odds of PCOS (Odds Ratio (OR): 0.10; 95% Confidence Interval (CI): 0.04 to 0.21, p for trend: <0.001). This association remained significant after adjustment for energy intake, marital status, pregnancy history, WC, chronic disease history, physical activity, and BMI (Odds Ratio (OR): 0.11; 95% (CI):0.05 to 0.27, p for trend: <0.001).ConclusionAlthough the present study found a significant protective association between adherence to LLDS and PCOS, more mechanism-based studies are needed to confirm these findings in the future.