1995 年 5 巻 2 号 p. 99-105
A hospital-based case-control study was conducted to examine changes in odds ratio of risk factors of breast cancer according to age group. Patients aged 30 to 69 years were selected as subjects. Cases were 1, 110 female patients with breast cancer diagnosed during 1988 to 1992 at Aichi Cancer Center Hospital. Controls were 20, 044 first-visit non-cancer patients during the same period. Logistic model was applied separately to the four age groups (30-39 years, 40-49 years, 50-59 years and 60-69 years at first visit), to estimate odds ratios of reproductive history, family history of breast cancer, body mass index, smoking, and drinking habits. Late menarche tended to give an odds ratio below unity in the age groups older than 50 years. Child birth and age at first delivery were significant risk factors for all four age groups. Odds ratio of having a sister with breast cancer was consistently high among the four age groups, while that of having mother with breast cancer was not. Body mass index over 24 was found to significantly increase the risk in age group 60-69. In age group 40-49, the smoking and drinking habits significantly increased the risk. These findings suggested the attribution of the risk factors to breast cancer could not always be similar among the age groups. J Epidemiol, 1995; 5 : 99-105.