Body mass index variability and pancreatic cancer risk in South Korean adults: a nationwide cohort study

Background: Although obesity is a known risk factor for pancreatic cancer, the role of dynamic weight fluctuations remains unclear. We examined whether body mass index (BMI) variability is associated with pancreatic cancer risk in a large South Korean cohort. Methods: We analyzed data from 232,322 participants in the Korean National Health Insurance Service database who underwent three health examinations between 2002 and 2007. Participants were followed from 2008 until pancreatic cancer diagnosis, death, or the end of the study period in 2019. BMI variability, assessed using average successive variability, was categorized into tertiles. We used Cox proportional hazards models to calculate adjusted hazard ratios and 95% confidence intervals after adjusting for potential confounders. Sensitivity analyses were performed to verify the robustness of our findings. Results: In the overall cohort, BMI variability showed no significant association with pancreatic cancer risk. However, a statistically significant interaction by sex was observed (P for interaction=0.029), yielding higher risk estimates among male participants. Conclusion: Although BMI variability lacked a significant overall association with pancreatic cancer risk, the attenuation of this risk after longer washout periods suggests the potential influence of preclinical weight changes. Nevertheless, the observed effect modification by sex indicates that BMI variability may retain clinical relevance for specific demographic groups, particularly male participants. Therefore, BMI variability should be interpreted not as a direct causal risk factor or intervention target, but as a potential clinical marker that warrants closer monitoring in these specific groups.