Age at Menarche and Breast Cancer

Summary

The results of a case-control study in the Katowice and Opele Districts of Poland are presented. The proportion of females with “late” menarche (age ≥ 16 years), both cases and controls , was similar to the proportion reported for Tokyo and much higher than in Athens or Boston, where breast cancer incidence is also higher. Females reporting menarche at ages < 6 years had breast cancer risks 1.76 as high as those reporting “late” menarche. This differential in risk was more marked for women up to 44 years of age than for older women. Other sources indicate an increase of the low breast cancer risk in Poland and also a decrease of the proportion of late menarche. A relation between geographic and secular variation in breast cancer occurrence and in menarche pattern is discussed. Age at menarche and breast cancer risk are probably indirectly associated, with nutrition being the possible common factor.