Background: Despite potentially relevant chemical differences between filtered and boiled coffee, this study is the first to investigate consumption in relation to the risk of incident cancer.
Methods: Subjects were from the Västerbotten Intervention Project (64,603 participants, including 3,034 cases), with up to 15 years of follow-up. Hazard ratios (HR) were calculated by multivariate Cox regression.
Results: No associations were found for all cancer sites combined, or for prostate or colorectal cancer. For breast cancer, boiled coffee ≥4 versus <1 occasions/day was associated with a reduced risk (HR = 0.52, CI = 0.30-0.88, p (trend) = 0.247). An increased risk of premenopausal and a reduced risk of postmenopausal breast cancer were found for both total (HR(premenopausal) = 1.69, CI = 0.96-2.98, p (trend) = 0.015, HR(postmenopausal) = 0.60, CI = 0.39-0.93, p (trend) = 0.006) and filtered coffee (HR(premenopausal) = 1.76, CI = 1.04-3.00, p (trend) = 0.045, HR(postmenopausal) = 0.52, CI = 0.30-0.88, p (trend) = 0.045). Boiled coffee was positively associated with the risk of respiratory tract cancer (HR = 1.81, CI = 1.06-3.08, p (trend) = 0.084), a finding limited to men. Main results for less common cancer types included total coffee in renal cell cancer (HR = 0.30, CI = 0.11-0.79, p (trend) = 0.009) and boiled coffee in pancreas cancer (HR = 2.51 CI = 1.15-5.50, p (trend) = 0.006).
Conclusion: These findings demonstrate, for the first time, the potential relevance of brewing method in investigations of coffee consumption and cancer risk, but they must be confirmed in future studies.