We conducted an updated meta-analysis to summarize the evidence from published studies regarding the association of coffee and caffeine intake with breast cancer risk.
Pertinent studies were identified by a search of PubMed and by reviewing the reference lists of retrieved articles. The fixed or random effect model was used based on heterogeneity test. The dose–response relationship was assessed by restricted cubic spline model and multivariate random-effect meta-regression.
37 published articles, involving 59,018 breast cancer cases and 966,263 participants, were included in the meta-analysis. No significant association was found between breast cancer risk and coffee (RR = 0.97, P = 0.09), decaffeinated coffee (RR = 0.98, P = 0.55) and caffeine (RR = 0.99, P = 0.73), respectively. And the association was still not significant when combining coffee and caffeine (coffee/caffeine) (RR = 0.97, P = 0.09). However, an inverse association of coffee/caffeine with breast cancer risk was found for postmenopausal women (RR = 0.94, P = 0.02), and a strong and significant association of coffee with breast cancer risk was found for BRCA1 mutation carriers (RR = 0.69, P b 0.01). A linear dose–response relationship was found for breast cancer risk with coffee and caffeine, and the risk of breast cancer decreased by 2% (P = 0.05) for every 2 cups/day increment in coffee intake, and 1% (P = 0.52) for every 200 mg/day increment in caffeine intake, respectively.
Findings from this meta-analysis suggested that coffee/caffeine might be weakly associated with breast cancer risk for postmenopausal women, and the association for BRCA1 mutation carriers deserves further investigation.