Cumulative abdominal obesity exposure and progressive risk of endometrial cancer in young women: a nationwide cohort study.

Background: The incidence of endometrial cancer has been rising sharply among younger generations, paralleling the growing obesity epidemic in this age group. Abdominal obesity is currently being investigated as an indicator of adiposity and cancer risk, and its prevalence is increasing in young women. This study aimed to examine whether cumulative abdominal obesity exposure in young women was associated with the development of endometrial cancer.

Methods: We used data from the South Korean National Health Insurance Service for women aged 20-39 years who had completed four consecutive annual health examinations between 2009 and 2012 and had no history of cancer at baseline. Participants were categorized into five groups based on the number of abdominal obesity exposures (waist circumference ≥ 85 cm). Exposure numbers ranged from 0 to 4, indicating the frequency of abdominal obesity across the four health examinations over 4 years. The primary outcome was newly diagnosed endometrial cancer, which was monitored until 2020, with a follow-up period of 7.12 years.

Results: Among the 445,791 young women (mean [SD] age 30.82 [4.55] years), 302 (mean [SD], 32.79 [4.53] years) developed endometrial cancer. The cumulative incidence of endometrial cancer differed significantly according to the number of abdominal obesity exposures (log-rank test, P < .001). The incidence of endometrial cancer has progressively increased with abdominal obesity exposure. The multivariable-adjusted HRs for incident endometrial cancer were 1.480 (95% CI, 0.970-2.258), 2.361 (95% CI, 1.391-4.008), 4.114 (95% CI, 2.546-6.647), and 6.215 (95% CI, 4.250-9.088) for participants with exposure numbers of 1-4, respectively, compared with those with an exposure number of 0.

Conclusion: In this population-based nationwide cohort study of young women, we observed a progressive increase in the risk of endometrial cancer with cumulative abdominal obesity exposure.