Joint association of drinking alcohol and obesity in relation to cancer risk: A systematic review and data synthesis.

Background: Rates of alcohol consumption and obesity are increasing in many Western populations. For some cancer types, both heavy alcohol consumption and obesity are independently associated with increased risk. Whether combined exposure to both synergistically increases an individual's risk of cancer is unclear. We performed a systematic review to assess whether alcohol and obesity interact to confer higher risk for cancer than the additive sum of their effects.

Methods: A systematic literature search was conducted from the inception date to 13 February 2024 of PubMed, Embase, Cochrane Library and Web of Science to identify studies of alcohol, obesity, and cancer risk. We aimed to undertake a meta-analysis if there were sufficient data.

Results: The literature search identified 17,740 potentially eligible studies. After review, 24 studies were included. Eleven reported on the association between alcohol consumption and cancer risk in individuals according to their body mass index (BMI), nine reported on the association between BMI and cancer risk in individuals according to their alcohol consumption, and six studies examined potential synergistic interactions between alcohol consumption and obesity on cancer risk. However, there were insufficient data and significant heterogeneity in the cancers studied to undertake meta-analysis, therefore a systemic review and narrative synthesis was conducted. Overall, there was no consistent pattern of interaction between alcohol use and overweight/obesity on cancer risk across cancer types.

Conclusions: While alcohol and obesity are prevalent and important risk factors for a range of cancers, data are lacking on whether their combined exposure may synergistically increase an individual's risk for cancer. Further study across more cancer types is required to better understand the nature of interactions between alcohol use and obesity on cancer risk.