Sex differences in the association between Korean Healthy Eating Index and type 2 diabetes mellitus in Korean adults: a prospective cohort study.

Objectives: Dietary quality is a modifiable determinant of type 2 diabetes mellitus (T2DM). However, evidence on the Korean Healthy Eating Index (KHEI) and sex-specific differences in its association with T2DM risk remains limited. This study is to examine the longitudinal association between KHEI and incident T2DM in Korean adults, with a focus on potential sex differences. Methods: We analyzed 56,000 adults (37,684 women and 18,316 men) from the Health Examinee cohort of the Korean Genome and Epidemiology Study. Dietary intake was assessed using a validated semi-quantitative food frequency questionnaire, and KHEI scores were constructed based on national guidelines. Incident T2DM was defined using physician diagnosis, treatment history, or biochemical criteria. Cox proportional hazards models and restricted cubic spline analyses were applied to evaluate associations, with adjustments for demographic, lifestyle, and clinical covariates. Results: Over a median follow-up of 4.2 years, 2,252 women and 1,776 men developed T2DM. Women in the highest quartile of KHEI had a 18% lower risk of T2DM compared with those in the lowest quartile (hazard ratio [HR]: 0.82, 95% confidence interval [CI]: 0.71-0.93; Conclusion: Higher diet quality, as measured by the KHEI, was associated with a reduced risk of T2DM in women but not in men, suggesting sex-specific effects of dietary patterns on diabetes prevention. These findings highlight the need for tailored nutritional strategies that consider biological and behavioral differences between women and men in Korea.