Coffee consumption and liver cancer risk in Japan: a meta-analysis of six prospective cohort studies

Previous epidemiological studies have shown that coffee consumption may reduce liver cancer risk. The present study aimed to summarize the evidence for this association in the Japanese population by performing a meta-analysis of the results of relevant cohort studies conducted in Japan. We searched studies published prior to September 1, 2018 in PubMed. Extracted data were analyzed using a random effects model. A total of six cohort studies from five publications were included in the final analysis. The pooled estimate of relative risk with 95% confidence interval (CI) for the group with highest coffee consumption was 0.50 (95% CI: 0.38-0.66, p < 0.001) compared with non-coffee drinkers or those who almost never drink coffee. No evidence of publication bias was observed (p for Begg's test = 0.85). This meta-analysis suggested that coffee consumption among Japanese people has a significant role in preventing liver cancer.