Dr. Carrie M. Cottreau and her colleagues at the University of Pittsburgh in Pennsylvania say their research suggests that women who stay highly active throughout life are less likely than sedentary women to develop the deadly disease ovarian cancer. Their findings were reported in the October issue of Obstetrics and Gynecology. In a study of more than 2,100 women, researchers found that those who exercised more than six hours per week were 27 per cent less likely to develop ovarian cancer than women who exercised less than 1 hour each week. High activity levels protected women of all ages. However, less than one quarter of the women exercised at that level. Although exercise has been linked to a lower risk of breast cancer, its relationship to ovarian cancer has been unclear. One study has even suggested regular exercise raises ovarian cancer risk, Cottreau's team notes. However, highly active women in this study consistently showed lower ovarian cancer risk across all age groups, from age 20 to 69. The researchers speculate that exercise cuts the cancer risk by preventing obesity or through its effects on hormones. For instance, active women tend to ovulate less often than other women. In addition, exercise can boost tumor-suppressing hormones, while inhibiting those that promote tumor growth. On the other hand, the authors note, exercise could be a marker for a generally healthful lifestyle. They did not assess the women's diets or other lifestyle factors.