As reported by the Journal Gazette, Fort Wayne, Indiana, October 29, 2006.

Sleep Studies

Sleep driven

Just as Americans can lay part of the blame for their eating patterns on the food processing industry and part of the blame for their sedentary lifestyle on unwalkable suburbs and sprawling cities, part of the blame for not quite enough sleep lies with congested highways and homes located far from work.

David F. Dinges of the University of Pennsylvania’s School of Medicine studied numbers from the U.S. Department of Labor’s American Time Use Survey, conducted in 2003, to find what Americans were doing instead of sleeping. He thought that, after time spent working, the next biggest temptation would come from television, computers and entertainment. Not so. “Here’s the big surprise. The more time you spend in the car, for any reason, the less you sleep,” Dinges said.

Someone who spends a total of 40 minutes in the car each day – that’s a round-trip commute plus all daily car errands – gets a good seven to eight hours of sleep. He reported those unpublished findings at the June meeting of Associated Professional Sleep Societies. And he found that for every eight minutes in the car beyond that, sleep time drops by about 15 minutes.

Heart needs a rest, too

The brain controls a lot, but the ever-beating heart needs sleep, too. During the night, the heart gets a break. Most people experience a 20 percent to 30 percent reduction in blood pressure, and a 10 percent to 20 percent drop in heart rate when they’re asleep, according to 24-hour blood pressure studies of more than 5,000 people by Dr. William White at the University of Connecticut Health Center.

Sleep is so important for the heart that, in a study published in the Aug. 2 issue of the journal Sleep, researcher Dr. Daniel J. Gottlieb of Boston University School of Medicine suggested that a good night’s sleep should be tested as a non-pharmacologic treatment in managing high blood pressure. He questioned more than 5,000 men and women ages 40 to 100 on their sleep habits and found that people sleeping fewer than six hours had as much as a 66 percent greater prevalence of hypertension.

Sleep deprivation linked to some cancers

Some cancers might be rooted in sleep deprivation – or, more precisely, to too many hours exposed to artificial light, according to Richard G. Stevens, cancer researcher at the University of Connecticut Health Center. His work is based on the theory that the increase in breast cancer in the industrialized world is linked to the disruption of hormone cycles.

Light, he says, suppresses production of the hormone melatonin, which allows levels of estrogen to rise. And, when lights are on long after dark, it confuses women’s circadian clocks, the roughly 24-hour internal rhythm that keeps hormones and organs on their daily schedule. “Cells don’t know when not to divide,” he says.

His theory was bolstered by a 1991 Centers for Disease Control and Prevention report showing that blind women are about half as likely as sighted women to get breast cancer. An Oct. 15, 2005, study in Cancer Research looked at sleep patterns of more than 12,000 women. Although researchers found no statistically significant increase in cancer risk among short sleepers, says Stevens, an author of the study, the risk estimates were consistently lower in long sleepers.

“We don’t know why breast cancer is increasing in industrialized societies,” he says. Until more is known, he advises women to get adequate sleep – and to do it in a very dark room.