Exercise plus sleep may lower cancer risk in women

Regular physical activity may lower a woman's overall risk of cancer, suggests a new government study -- but only if her workouts don't cut into a good night's sleep. Otherwise, lack of shut-eye appears to cancel out much of exercise's protective benefits.

The link between physical activity and a reduced cancer risk is well established, says James McClain, Ph.D., a cancer prevention fellow at the National Cancer Institute and lead author of the study. So far, there is little evidence that sleep affects cancer risk, but not getting enough does appear to negatively affect many of the same hormonal, immune, and metabolic functions in the body that exercise is known to improve.

McClain's study -- presented at the American Association for Cancer Research's seventh annual conference -- followed 5,968 women for almost 10 years, during which 604 of them developed some form of cancer. Based on self-reported data, those in the top half of physical activity levels showed about a 20 percent reduction in cancer risk compared with those who exercised less frequently. How one woman with breast cancer is (still) handling a difficult recovery

Among the more active women 65 and younger, however, those who slept for fewer than seven hours a night saw much of that benefit negated. Their cancer risk was greater than those who exercised but slept more -- but still lower than those who exercised the least.

"When you look at the previous research on physiological effects associated with increasing activity as opposed to sleeping adequately, you can see they appear to go in different directions," McClain says. "Though this was a small study, it supports the hypothesis that sleep might modify the relationship between physical activity and cancer."

Many health problems have been linked to a lack of sleep, says David Rapoport, M.D., director of the Sleep Medicine Program at New York University's Langone School of Medicine. Should you take sleeping pills?

Even short periods of sleep deprivation can promote glucose intolerance, increasing a person's risk for diabetes. It can also cause imbalances in ghrelin and leptin hormone levels -- which regulate appetite -- prompting people to overeat and gain weight. Research also suggests that it can increase C-reactive protein (a marker of inflammation and known risk for cardiovascular problems) in the blood, alter coagulation and platelet function, and raise blood pressure.

Source: http://www.cnn.com/2008/HEALTH/conditions