Too much sleep may boost cancer risk

The study presented at the American Association for Cancer Research confirmed previous findings that people who do regular physical activity are less likely to develop cancer.

They also discovered women who slept less than seven hours nightly had a 47 percent higher risk of cancer than those who got more sleep among the physically active women.

Experts say, the effects of exercise on the body's hormone levels and immune function play a role in reducing cancer risks, but they don't know why lack of sleep may make one more susceptible to cancer.