Posts Tagged ‘ sleep ’

Lost Sleep Is Hard to Find

Erin O’Donnell in Harvard Magazine:

it’s a time-honored practice among medical residents, cramming undergrads, and anyone else burning the candle at both ends: get very little sleep for days, maybe even pull an all-nighter, and then crash for an extra-long night of shut-eye to catch up.

Ten hours of sleep at once may indeed recharge us, and allow us to perform well for several hours after waking, according to research recently published inScience Translational Medicine. But “the brain literally keeps track of how long we’ve been asleep and awake—for weeks,” says Harvard Medical School (HMS) neurology instructor Daniel A. Cohen, M.D., lead author of the study. And that means that the bigger our aggregate sleep deficit, the faster our performance deteriorates, even after a good night’s rest.

Cohen and his coauthors monitored nine young men and women who spent three weeks on a challenging schedule: awake for 33 hours, asleep for 10—the equivalent of 5.6 hours of sleep a day. (This approximates the schedule of a medical resident, but many of us live under similar conditions; the National Sleep Foundation reports that 16 percent of Americans sleep six or fewer hours a night.) When the study participants were awake, they took a computer-based test of reaction time and sustained attention every four hours.

The researchers were surprised to discover just how much an extended rest boosted test performance. “Even though people were staying awake for almost 33 hours, when they had the opportunity to sleep for 10 hours, their performance shortly after waking was back to normal,” Cohen says. “The really interesting finding here is that there’s a short-term aspect of sleep loss that can be made up relatively quickly, within a long night.”

But the days and weeks of lost sleep eventually took their toll. The investigators knew from previous research that people awake for 24 hours straight display reaction times comparable to those of people who are legally drunk. Cohen’s new study reveals that those who pull an all-nighter on top of two or three weeks of chronic sleep loss reach that level of severe impairment faster—after just 18 hours awake.

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Left-sided Cancer: Blame your bed and TV?

R. Douglas Fields in Scientific American:

Curiously, the cancer rate is 10 percent higher in the left breast than in the right. This left-side bias holds true for both men and women and it also applies to the skin cancer melanoma. Researchers Örjan Hallberg of Hallberg Independent Research in Sweden and Ollie Johansson of The Karolinska Institute in Sweden, writing in the June issue of the journal Pathophysiology, suggest a surprising explanation that not only points to a common cause for both cancers, it may change your sleeping habits.

For unknown reasons the rates of breast cancer and melanoma have both increased steadily in the last 30 years. Exposure to the sun elevates the risk of melanoma, but the sun’s intensity has not changed in the last three decades. Stranger still, melanoma most commonly affects the hip, thighs and trunk, which are areas of the body protected from the sun. What is responsible for the left-side dominance and increasing incidence of these cancers?

An intriguing clue comes from the Far East. In Japan there is no correlation between the rates of melanoma and breast cancer as there is in the West, and there is no left-side prevalence for either disease. Moreover, the rate of breast cancer in Japan is significantly lower than in the West; only 3 percent of what is seen in Sweden, for example. The rate of prostate cancer in Japan is only 10 percent of that in the U.K. and U.S.

The researchers suggest an explanation based on differences in sleeping habits in Japan and Western countries. Previous research has shown that both men and women prefer to sleep on their right sides. The reasons for this general preference are unclear, but sleeping on the right side may reduce the weight stress on the heart, and the heartbeat is not as loud as when sleeping on the left. Still, there is no reason to suspect that people in Japan sleep in positions that are any different from those in the West. The beds in Japan, however, are different. The futons used for sleeping in Japan are mattresses placed directly on the bedroom floor, in contrast to the elevated box springs and mattress of beds used in the West. A link between bedroom furniture and cancer seems absurd, but this, the researchers conclude, is the answer.

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