Introduction To investigate the risk of gynecologic cancers according to obesity and menopausal status using a nationwide cohort in Korea.

Methods We identified 2,708,938 women from the National Health Insurance Service cohort, and obtained baseline body mass index (BMI), waist circumference (WC), and other healthcare data, measured and collected during a health examinations and cancer-screening survey. By setting a normal weight/WC group (BMI, 18.5–22.9 kg/m2 or WC, 80.0–84.9 cm) as the reference, we conducted multivariate analyses.

Results The total follow-up duration was 22389854.63 person-years. In post-menopausal women, as the BMI classification level increased from normal to class II obesity, the risk of endometrial cancer (aHR, 2.11; 95% CI, 1.81–2.46) and ovarian cancer (aHR, 1.38; 95% CI, 1.20–1.58) significantly increased. The risk of endometrial cancer also increased as the WC classification increased from <75.0 to ≥95.0 cm. With a WC of 80.0–84.9 cm as the reference, the lowest risk of endometrial cancer was observed in WC <75.0 cm (aHR, 0.75; 95% CI, 0.67–0.84) while the highest risk was observed in WC ≥95.0 cm (aHR, 1.56; 95% CI, 1.33–1.82). In pre-menopausal women, the trends of endometrial and ovarian cancer incidence in pre-menopausal women were similar to those observed in post-menopausal women. For cervical cancer, only class II obesity was significantly associated with increased risks in both post-menopausal women (aHR, 1.18; 95% CI, 1.01–1.39) and pre-menopausal women (aHR, 1.27; 95% CI, 1.02–1.57).

Conclusion/Implications In Korean women, the impact of obesity on the development of gynecologic cancers differs according to the malignancy type and menopausal status.