Alcohol consumption is a risk factor for breast cancer (BC), yet little is known about longitudinal alcohol consumption patterns and risk of BC. This study aimed to investigate whether trajectory profiles of alcohol consumption across adulthood were associated with risk of first primary malignant BC in postmenopausal women. At baseline, 28,720 pre-and postmenopausal women aged 50-65 years from the Danish Diet, Cancer and Health Cohort reported their average alcohol intake over the past 12 months and their average alcohol intake at the ages of 20, 30, 40, and 50 years. Alcohol consumption trajectories were estimated using latent class mixed models. BC cases were identified through record linkage to the Danish Cancer Registry. To examine associations between alcohol consumption trajectories and BC, we fitted a proportional hazard model adjusted for potential confounding factors using data from 24,543 postmenopausal women without missing covariate information. We identified 4 alcohol consumption trajectory profiles. During a median follow-up of 16.5 years, 1,591 cases of BC occurred. A mean alcohol consumption trajectory of > 10 g/day was associated with higher risk of BC (HR: 1.65, 95%CI: 1.35-2.03) compared to a mean alcohol consumption trajectory of < 6 g/day. We found no association between trajectory profiles characterized by lower alcohol intakes in early adulthood followed by increasing consumption of alcohol in adulthood compared to a consistently low intake of alcohol. Postmenopausal women drinking consistently high amounts of alcohol throughout adulthood had a higher risk of BC compared to women with a consistently low intake of alcohol.< Réduire