Sex Differences in the Effect of Changes in Body Mass Index on the Risk of Developing Gastric Cancer: Findings from a Nationwide Retrospective Cohort Study.

Background/aims: This study examined sex differences in the effect of changes in body mass index (BMI) on the development of gastric cancer (GC) in South Korea.

Methods: Using data from the National Health Insurance Service-Health Screening Cohort, a retrospective cohort study involving 333,169 Koreans with a median follow-up of 12 years was conducted. BMI was categorized into five groups (<18.5, 18.5-22.9, 23.0-24.9 [reference], 25.0-29.9, and ≥30.0 kg/m²) and the risk of developing GC was evaluated according to changes in BMI by calculating the hazard ratio (HR) using Cox proportional hazard regression.

Results: Among males, BMI ≥30.0 kg/m² was associated with a 1.27-fold higher overall risk of developing GC (95% confidence interval [CI], 1.02 to 1.57), but not in females. For non-cardia GC, a U-shaped association between BMI and risk of developing GC was observed in males, although statistical significance was observed only for BMI 18.5-22.9 kg/m². Additionally, an increase in BMI to 23.0-24.9 kg/m² was associated with a decreased non-cardia GC risk among males. In females, the largest waist circumference category was significantly associated with an increased risk of developing overall GC (HR, 1.37; 95% CI, 1.07 to 1.74).

Conclusions: This study demonstrated that maintaining a BMI in the range of 23.0-24.9 kg/m² is optimal for minimizing the risk of non-cardia GC, particularly in males. In females, visceral obesity, represented by a large waist circumference as a proxy, was associated with an increased risk of developing GC.