Body mass index and gastrointestinal cancer mortality in Korean adults: A prospective cohort study

Background The association between body mass index (BMI) and mortality from gastrointestinal (GI) cancer remains unclear, especially in Asian populations. Methods A total of 510 148 Korean adults who participated in routine health examinations during the period 2002–2003 were followed up until 2013. Results During a mean follow up of 10.5 years, 7831 individuals died of GI cancer. Various associations with BMI were found: U‐curve (overall GI, colorectal, liver, and gallbladder cancer), L‐curve (stomach cancer), linear (esophageal, extrahepatic bile duct [EBD], and small intestine cancer), and none (pancreatic cancer). Overall GI cancer mortality was lowest at approximately 23.5–26 kg/m 2 . For cancers with linear associations, the multivariable adjusted hazard ratios per each 5 kg/m 2 higher BMI were 0.53 (95% confidence interval = 0.43–0.65, esophagus), 1.19 (1.02–1.40, EBD), and 0.64 (0.41–0.999, small intestine). For cancers with U‐curve or L‐curve associations, the corresponding hazard ratios ≥25 kg/m 2 were 1.19 (1.08–1.32, overall GI), 1.30 (1.04–1.64, colorectal), 1.28 (1.07–1.53, liver), and 1.30 (0.85–1.97, gallbladder), while in the range of <25 kg/m 2 , they were 0.81 (0.76–0.87, overall GI), 0.43 (0.32–0.58, esophagus), 0.70 (0.62–0.79, stomach), and 0.77 (0.65–0.90, colorectal), and these inverse associations did not weaken after excluding the first 7 years of follow up and ever smokers. Conclusions Both low and high BMIs were associated with excess mortality from GI cancers in Korean adults. EBD cancer had a positive association, while esophageal and small intestine cancers had inverse associations. Above 25 kg/m 2 , liver and colorectal cancers had positive associations with BMI, whereas below 25 kg/m 2 , stomach and colorectal cancers had inverse associations.