Sleep may affect cancer-protective effects of physical activity in women

AACR Frontiers in Cancer Prevention Research

Women who participate in regular physical activity and get adequate sleep may reduce their overall risk for cancer, according to prospective data presented at the AACR Seventh Annual International Conference on Frontiers in Cancer Prevention Research.

“These findings highlight the importance of being physically active with respect to cancer risk and suggest that sleep is particularly important in women who exercise,” James J. McClain, PhD, MPH, of the National Cancer Institute, said during a press conference.

McClain and colleagues reviewed surveys taken in 1998 from 5,968 women aged 18 years or older with no previous cancer diagnosis. The researchers followed the women for almost 10 years to determine the association between physical activity energy expenditure, sleep duration and incidence of overall breast and colon cancers.

First incidence of cancer occurred among 604 women, 186 of which were breast cancer cases. According to McClain, sleep duration altered the association between physical activity and cancer risk among this population.

The risk for overall cancer (HR=0.80; 95% CI, 0.68-0.95) and breast cancer (HR=0.75; 95% CI, 0.55-1.01) was lower among women in the upper 50% of physical activity energy expenditure compared with those in the lower 50%.

Women in the upper 50% aged 65 years or younger at baseline who slept less than seven hours per day had a 1.5-fold increase in their overall risk for cancer (HR=1.47; 95% CI, 1.05-2.06). Much of the protective effects of physical activity were canceled out by inadequate sleep. – by Stacey L. Adams

For more information:

McClain J. #B145. Presented at: AACR Seventh Annual International Conference on Frontiers in Cancer Prevention Research; Nov. 16-18, 2008; Washington.