Alcohol consumption and colorectal cancer risk in prediabetes and diabetes: a nationwide cohort study.

BACKGROUND: The impact of light-to-moderate alcohol consumption on colorectal cancer (CRC) risk remains uncertain. We examined whether a dose-response association exists between alcohol consumption and CRC risk and whether it differs by glycemic status. METHODS: A nationwide cohort of 4,475,492 adults undergoing health screening provided by Korean National Health Insurance Service in 2012 was analyzed. Participants were followed until CRC development, death, or December 31, 2022 (median follow-up, 9.33 years). Alcohol intake was categorized as none, light-to-moderate (male, <30 g/day; female, <20 g/day), or heavy. Incident CRC identified using ICD-10-CM and cancer-specific reimbursement codes served as the primary outcome. RESULTS: During follow-up, 51,592 participants developed CRC. Worse glycemic status was significantly associated with increased risk of CRC (hazard ratio [HR], 1.11 [95% CI, 1.09-1.13] for impaired fasting glucose (IFG); HR, 1.26 [95% CI, 1.23-1.29] for diabetes). Light-to-moderate alcohol consumption significantly and synergistically increased CRC risk in individuals with IFG (HR, 1.23 [95% CI, 1.19-1.27]; synergy index, 1.72 [95% CI, 1.40-2.04]) and in those with diabetes (HR, 1.48 [95% CI, 1.42-1.54]; synergy index, 2.04 [95% CI, 1.84-2.25]). Greater alcohol intake amount and frequency showed a linear dose-response association with increased risk of all subsites of colorectal cancer across all glycemic categories (except normoglycemia for proximal colon cancer), with the steepest gradient for diabetes. CONCLUSIONS: Even light-to-moderate alcohol consumption was associated with increased CRC risk; therefore, strict restriction of alcohol intake may help reduce this risk, particularly among individuals with IFG or diabetes.