Alcohol consumption and incidence of prostate cancer among Chinese people: A systematic review and meta-analysis

Aims: Meta-analyses have suggested a dose-response relationship between level of alcohol use and risk of prostate cancer, but the populations in the included studies are predominantly Caucasian. Many Chinese language studies have not been included in published reviews and/or meta-analyses. The present meta-analysis accessed research reports in both English and Chinese language sources in order to investigate this relationship specifically among Chinese people. Methods: Searches in five large Chinese biomedical bibliographic databases were made for case-control and cohort studies of alcohol consumption and prostate cancer incidence and death (ICD-10: C61) up to May 2017. Studies were coded for design, outcome, drinker and non-drinkers, extent of control for confounding and other study characteristics. Mixed models were used to estimate relative risk (RR) of incidence or death from prostate cancer due to alcohol consumption with study level controls for designs, drinker bias and types of drinkers. Findings: A total of 415 studies were identified of which 25 (20 in Chinese from five Chinese databases and 5 in English from published meta- analyses) satisfied inclusion criteria providing 36 risk estimates of prostate cancer for drinkers versus non-drinkers. There was a total of 36 OR estimates; 27 using patients as controls and 9 using healthy people. Nine studies (14 OR estimates) specified reference abstainers as "never drank" or "no drinking". Adjusted RR estimates indicated a significantly increased risk of prostate cancer among drinkers (RR=1.46, 95% CI: 1.40 - 1.52, t-test P<0.001) compared to non-drinkers. Dose-response relationships (t-test P<0.001) were evident in three studies that assessed level of alcohol intake. Conclusions: There is a significantly higher risk of prostate cancer incidence among Chinese drinkers than non-drinkers, with some evidence of a dose-response relationship. However, almost all the identified studies suffered from former and/or occasional drinker biases. Few studies had adequate measures of level of alcohol intake and further well-designed studies are required.