Physical activity patterns and breast cancer mortality among postmenopausal females: Findings from the NHIS 1990 to 1991

The author used data from the 1990 and 1991 National Health Interview Survey (NHIS) to examine the association between self-reported leisure-time physical activity (LTPA) and breast cancer mortality. This cohort study included 16,009 women 55 years of age and older; during an average 8 years of follow-up, 149 deaths occurred attributed to breast cancer. Mortality was determined through the linking of the NHIS and the National Death Index (NDI). Conditional logistic regression analysis was used to estimate odds ratio (ORs) and 95 percent confidence intervals (95% CI). After adjustment for potential confounding factors (age, race, marital status, education, health status, body mass index (BMI), alcohol consumption, and smoking), LTPA was associated with a reduced mortality of breast cancer in a dose-response manner. OR for breast cancer for women who participated in LTPA 1--2 times per week was 0.90 (95% CI = 0.51, 1.58), for women who participated 3--4 times per week was 0.69 (95% CI = 0.44, 1.07) and for women who participated 5 or more times per week or vigorous 3 times or more was 0.51 (95% CI = 0.28, 0.91), as compared to women that were inactive. Breast cancer mortality was also associated with levels of education and health status. Women with less than a high school education had reduced mortality of breast cancer (ORs 0.50; 95% CI = 0.32, 0.79) when compared to those women who had more than a high school education. Women who self-reported a poor or fair health status had an increased mortality of breast cancer, ORs 4.26, 95% CI = 1.91, 9.49 and ORs 2.04, 95% CI = 1.02, 4.06 respectively. No association was found in age, race, BMI, alcohol consumption, and smoking. The finding support a protective effect of LTPA on breast cancer mortality in postmenopausal women.