Review on December 10, 2009
Aside from the obvious health benefits associated with long term physical activity, it is believed there is a beneficial aspect of exercise in relation to the risk of breast cancer. As breast cancer is a leading cause of death in American women it is important that studies are conducted to determine what can combat this disease and stop it from killing so many women. The amount of menstrual periods a woman has, and her exposure to estrogen can affect the level of a woman's breast cancer risk. To determine the effects of long term physical activity on breast cancer (in correspondence to menstrual periods), this study was conducted using information from the California Teacher's Study.
Participants of the California Teacher's Study was studied to learn of the relationship between recreational physical activity and the danger of invasive and situ breast cancer. Invasive cancer breaks through the normal breast tissue barrier and spreads to neighboring areas in the breast and possibly to other areas of the body. Situ breast cancer is non-invasive meaning the cancer cells stay in the same place without spreading to surrounding tissues in the breast or other parts of the body.
Measures of Recreation Physical Activity
From the California Teacher's Study, 110,599 females aged 20 - 79 years took part. They had no history of breast cancer at baseline and were observed from 1995 - 2002. They gave data of personal participation/involvement of strenuous and moderate recreational activities during the menstrual periods from the time of high school until the age of 54. Examples of moderate activities included brisk walking, golf and volleyball while strenuous activities included swimming laps, aerobics, running and jogging. They also reported participation levels in terms of weeks, months and years.
Breast Cancer Risk Factors
Members also reported information of breast cancer risk factors such as family history of breast cancer, ethnicity, reproductive history, regularity of menstrual periods, menopausal status, age at menarche, use of hormones therapy and oral contraceptives, weight, height, diet smoking status and alcohol consumption.
Women were determined premenopausal if they had menstrual periods during baseline, peri menopausal if menstrual periods stopped within six months of baseline and post menopausal if menstrual periods had stopped 6 months earlier/prior to baseline.
Two different models were used to evaluate the relationship between physical activity and invasive and in situ breast cancer. The results reported that having less menstrual periods, from strenuous physical activity lowered the risk of breast cancer development in women