Extremes of sleep related to increased fat around organs

A new study by researchers at Wake Forest University School of Medicine reveals how extremes of sleep -- both too much and too little -- can be hazardous to your health -- especially for young minority women, a group most affected by obesity and chronic metabolic disease. The findings also indicate that there's more to "fat" than what we choose to eat -- social factors such as the need to work three jobs in a bad economy -- could be causing dangerous fat deposition around vital organs.

"We put a lot of stock in diet," said Kristen G. Hairston, M.D., M.P.H., an assistant professor of endocrinology and metabolism and lead author on the study. "But this study brings up some interesting questions about the way we live. We may need to start looking at other behaviors -- besides daily food choices -- that could be contributing to the obesity epidemic in younger age groups."

In individuals under 40, the study showed a clear association between averaging five hours or less of sleep each night and large increases in visceral fat, or fat around the organs. Of the study participants under 40, Hispanic men and black women were the largest groups to report getting such little sleep.

Short sleep has become more common in the United States and minorities are disproportionately affected, said Hairston, an affiliate of the Maya Angelou Center for Health Equity, part of the School of Medicine. They are also more prone to metabolic conditions, including increased rates of obesity, insulin resistance and type 2 diabetes. The study suggests that part of the explanation for higher rates of metabolic disease in this population may lie in the association between sleep duration and fat deposition.

But sleeping the day away won't do much to better one's health, either. The researchers found that getting more than eight hours of sleep on average per night has a similar -- though less pronounced -- affect and is a problem most commonly seen in Hispanic women of all ages.

Surprisingly, the connection between extremes of sleep and accumulation of visceral fat was seen only in patients under 40, Hairston said.

"We don't really know yet why this wasn't seen in participants over 40, but it was clear that, in individuals under 40, it is worse to get five or less hours of sleep on average each night than it is to get eight or more hours," Hairston said. "However, both may be detrimental and, in general, people should aim for six to eight hours of sleep each night."

The study appears in the March issue of Sleep, the journal of the Associated Professional Sleep Societies, LLC.

The study raised important social questions for researchers, Hairston said, such as why so little sleep is such a problem in black women under age 40 and what circumstances may be contributing to their sleep patterns and likely to obesity and chronic disease development?

"This was certainly just a starting point," Hairston said. "We definitely know that a relationship exists between sleep and obesity. Now we need to know how this relationship can be modified."

Hairston added that it will be important for future obesity research to consider sleep patterns and the effect they can have on outcomes. Until the connection is understood, physicians should consider gathering information about sleep patterns just as they do other vital information when seeing patients. This information is especially relevant when treating patients about to make or in the middle of life transitions, such as college, marriage and childbearing, because such times are often associated with sleep deprivation in younger years.

"That information may help a physician put into context other issues going on in the patient's life which may be affecting their overall health," Hairston said.

Coresearchers on the study, funded by the National Institutes of Health, were Donald W. Bowden, Ph.D., and Lynne E. Wagenknecht, Dr.P.H., both of the School of Medicine, Michael Bryer-Ash, of the University of Oklahoma School of Health Sciences, Jill M. Norris, M.P.H., Ph.D., of the University of Colorado School of Health Sciences, and Steven Haffner, M.D., M.P.H., of the University of Texas Health Science Center at San Antonio.