ASSOCIATION OF BODY-MASS INDEX, PHYSICAL-ACTIVITY, AND REPRODUCTIVE HISTORIES WITH BREAST-CANCER - A CASE-CONTROL STUDY IN GIFU, JAPAN

To further clarify risk factors for breast cancer in Japanese women, a self-administered questionnaire was completed by 157 cases with histo logically confirmed breast cancer from 1989 to 1993 and by 369 age and residential area matched controls in Gifu, Japan. Conditional logisti c regression model was used to assess the relations. Multivariate anal yses showed that breast cancer risk decreased with body mass index for premenopausal women (RR = 0.45; 95% CI = 0.22-0.92 for BMI greater th an or equal to 23 vs. < 21 (kg/m(2))), but the risk increased with bod y mass index for postmenopausal women (RR = 1.98; 95% CI = 0.86-4.55 f or BMI greater than or equal to 24 vs. < 21.5 (kg/m(2))). The risk inc reased with a small number of births in pre- and post-menopausal women (1.83; 1.11-2.99 and 6.06; 2.40-15.3 for 1-2 births and nulliparity, respectively, vs. greater than or equal to 3 births). Ex- or current s moking increased the risk of breast cancer (2.31;1.19-4.49). Reduced r isk of premenopausal breast cancer was associated with high energy exp enditure in physical activity during teenage, although the trend was n ot statistically significant.