Breast cancer risk in male alcoholics in Sweden

Objective: To investigate the association between alcoholism and risk of male breast cancer. Methods: We conducted a retrospective population-based cohort study in Sweden of men diagnosed with alcoholism between 1965 and 1995. The cohort was followed up through interlinkages with nationwide registries (the national cancer registry, immigration registry, causes of death registry, and population registry), using the national registration numbers. Standardized incidence ratios (SIRs), calculated using the Swedish national cancer incidence rate as reference, were used as estimates of relative risks. Results: A total of 145,811 men were enrolled into the cohort, contributing 1,499,504 person-years of follow-up. Sixteen incident breast cancer cases were identified, and the mean age at diagnosis was 68 years. We excluded the first year of follow-up (cases and person-years) from the analysis to avoid detection bias. The overall SIR (excluding the first year of follow-up) was 1.1 (95% CI 0.6-2.0). Although based on small numbers we found no indication of a differential SIR according to duration of follow-up, age at cohort enrolment, or age at follow-up (attained age or age at cancer diagnosis). Conclusion: The observed associations are not compatible with an increase in breast cancer risk among male alcoholics.