Early‐life body size and risk of developing biliary tract cancers

BACKGROUND: Childhood body mass index (BMI) trajectories, BMI, height, and birth weight were investigated in relation to biliary tract cancer (BTC) risk in this population-based cohort study. METHODS: The study included 172,113 males and 168,503 females born between 1930 and 1996 from the Copenhagen School Health Records Register. Heights and weights measured at ages 6-15 years identified five sex-specific BMI trajectories. BMI and height were analyzed as z scores; overweight was defined via US Centers for Disease Control and Prevention criteria. Sex-specific hazard ratios (HRs) were estimated via birth cohort-stratified Cox regressions. RESULTS: During a median follow-up of 34.5 years, 635 individuals developed BTCs. Overweight (HR, 1.58; 95% confidence interval [CI], 1.06-2.34) and obesity trajectories in males (HR, 3.22; 95% CI, 1.61-6.44) and the obesity trajectory in females (HR, 2.88; 95% CI, 1.62-5.15) were associated with increased BTC risk compared with the average BMI trajectory. Childhood overweight at age 7 years was associated with increased intrahepatic bile duct cancer risk in males (HR, 2.66; 95% CI, 1.48-4.75) and extrahepatic bile duct cancer risk in females (HR, 3.83; 95% CI, 1.94-7.56). Taller childhood height was linked to a higher BTC risk in males only; birth weight showed no associations. CONCLUSIONS: Childhood overweight and obesity increase BTC risk in adulthood.