Coffee intake decreases risk of postmenopausal breast cancer: A dose-response meta-analysis on prospective cohort studies

Abstract: Aim: A dose-response meta-analysis was conducted in order to summarize the evidence
from prospective cohort studies regarding the association between coffee intake and breast cancer
risk. Methods: A systematic search was performed in electronic databases up to March 2017 to
identify relevant studies; risk estimates were retrieved from the studies and linear and non-linear
dose-response analysis modelled by restricted cubic splines was conducted. A stratified and subgroup
analysis by menopausal and estrogen/progesterone receptor (ER/PR) status, smoking status and
body mass index (BMI) were performed in order to detect potential confounders. Results: A total of
21 prospective studies were selected either for dose-response, the highest versus lowest category of
consumption or subgroup analysis. The dose-response analysis of 13 prospective studies showed
no significant association between coffee consumption and breast cancer risk in the non-linear
model. However, an inverse relationship has been found when the analysis was restricted to
post-menopausal women. Consumption of four cups of coffee per day was associated with a 10%
reduction in postmenopausal cancer risk (relative risk, RR 0.90; 95% confidence interval, CI 0.82 to
0.99). Subgroup analyses showed consistent results for all potential confounding factors examined.
Conclusions: Findings from this meta-analysis may support the hypothesis that coffee consumption
is associated with decreased risk of postmenopausal breast cancer.