Regular Moderate Exercise May Lower Ovarian Cancer Risk

Laurie Barclay, MD

May 16, 2005

May 16, 2005 — Increased physical activity is associated with reduced risks of some types of ovarian cancer, according to the results of a population study published online May 16 in the International Journal of Cancer.

"Although the evidence for a protective effect of physical activity on colon and breast cancer is convincing, the evidence for an inverse association between physical activity and ovarian cancer is insufficient," write Sai Yi Pan, from the Public Health Agency of Canada in Ottawa, Ontario, and colleagues from the Canadian Cancer Registries Epidemiology Research Group. "If proven to reduce ovarian cancer risk, physical activity — a modifiable lifestyle factor — could provide a method to prevent this fourth most common neoplasm in women, which has a poor prognosis."

Using data from a population-based study of 442 case subjects with histologically confirmed incident ovarian cancer and 2,135 control subjects aged 20 to 76 years, conducted from 1994 to 1997 in Canada, the authors investigated the effect of recreational and occupational physical activity on ovarian cancer risk. Self-administered questionnaires determined frequency and intensity of physical activity.

Compared with women in the lowest tertiles of moderate, vigorous, and total recreational activity, women in the highest tertiles had reduced risk of ovarian cancer. Multivariable-adjusted odds ratios were 0.67 (95% confidence interval [CI], 0.50 - 0.88), 0.93 (95% CI, 0.70 - 1.24), and 0.73 (95% CI, 0.58 - 0.98), respectively. Increasing levels of moderate and total recreational activity were associated with statistically significant trends of decreasing risk, with similar patterns for premenopausal and postmenopausal women.

Higher levels of moderate recreational activity were associated with significant reduction in risk for serous, endometrioid, and other tumors except for mucinous types. In one province with the largest number of case and control subjects, analyses suggested that occupational activity was associated with reduced ovarian cancer risk by lifetime activity and by various life periods (early 20s, early 30s, early 50s, and two years before interview).

"Our study suggests that occupational and regular moderate recreational physical activity reduce ovarian cancer risk," the authors write. "The greater risk reduction among overweight or obese women observed in our study supports the role of physical activity in affecting ovarian cancer risk through its effect on obesity and also [implies] that obese women would get more benefit from physical activity against ovarian cancer than lean women."

Study limitations include exclusion of 20.2% of cases before they could be sent questionnaires because of death or loss to follow-up, failure to return questionnaires in 24.0% of cases, possible recall bias, lack of data on duration of each activity, possible misclassification in histologic types, and lack of validation of the self-reported questionnaire.

"The reduction associated with recreational activity was similar among premenopausal and postmenopausal women; however, a significant decrease in risk was observed for serous, endometrioid and other but not mucinous histologic types of ovarian tumors," the authors conclude. "The results from one province also suggested that occupational activity afforded protection again ovarian cancer across various life periods."

Intl J Cancer. Published online May 16, 2005.

Reviewed by Gary D. Vogin, MD

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