MONDAY, Nov. 17, 2008 (Health.com) — 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, PhD, a cancer prevention fellow at the National Cancer Institute and lead author of the study. So far, there is little evidence that sleep impacts 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% reduction in cancer risk compared to those who exercised less frequently.
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.
Comments (2)
A Possible Explanation of the Connection of Poor Sleep and Increased Physical Exercise
Copyright 2008, James Michael Howard, Fayetteville, Arkansas
It is my hypothesis that low DHEA may trigger cancer (Annals of Internal Medicine 2005; 142: 471-472). Cancer occurs most often in old age when DHEA has declined to very low levels.
It is also my hypothesis that the function of sleep is to increase DHEA. Poor sleep would indicate a situation of poor DHEA production. While it is known that exercise increases DHEA and is the reason, I suggest, that exercise reduces cancer risk, exercise, according to my work, also uses DHEA. Individuals who exercise excessively, especially if they are not sleeping well and producing sufficient DHEA, might actually use more DHEA than they produce. This reduces DHEA and increases cancer risk.
I suggest this new finding that poor sleep and excessive exercise increase cancer risk is caused by an overall reduction in DHEA.
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