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NEW YORK (Reuters Health) - Adults who routinely get too little or too much sleep may die sooner than those who get the standard 8 hours each night, a study suggests.
Researchers found that among nearly 10,000 UK adults followed for 17 years, those who starting sleep less each night during the early part of the study were more likely to die of heart disease or stroke than those who kept catching 7 or 8 hours of sleep.
On the other hand, those whose typical sleep time increased beyond 8 hours were at elevated risk of dying from non-cardiovascular causes.
The study, published in the medical journal Sleep, did not pinpoint the reason for the findings.
However, past research suggests that chronic sleep deprivation can be hard on the cardiovascular system. Sleep is a time for the body to recoup, which includes drops in blood pressure and heart rate that ease the daily strain on the heart, explained Dr. Jane E. Ferrie of the University College London, the lead researcher of the new study.
In addition, she told Reuters Health, some studies have linked sleep deprivation to poorer appetite control and blood-sugar regulation, which can affect body weight and the risk of type 2 diabetes. This, in turn, could potentially increase a person's odds of developing heart disease.
It's possible that study participants who started sleeping less were in poorer health; certain conditions, such as any disorder that causes chronic pain, might curtail a person's sleep, Ferrie pointed out.
The study participants were asked about pre-existing illnesses at the outset, but it's possible that some had underlying health problems that were missed, according to Ferrie.
Similarly, it's not clear why people who slept more over time had a higher risk of dying from non-cardiovascular causes. Some medical conditions, like cancer or depression, can cause fatigue, Ferrie said. But the researchers lacked enough information to tell which specific causes of death were linked to increasing sleep times.
The findings are based on information from 9,781 British adults who were 35 to 55 years old when they enrolled in the study, between 1985 and 1989. The participants reported on their sleep habits at study entry and again 5-to-6 years later; they were then followed for another 12 years, on average.
Overall, Ferrie's team found, the risk of dying from cardiovascular disease was higher among men and women who started off sleeping 7 or 8 hours per night, but were getting less sleep a few years later. Their risk of cardiovascular death was double that of their peers who maintained the standard 7- to 8-hour sleep schedule.
Likewise, the risk of dying from non-cardiovascular causes doubled among people whose nightly sleep time increased from an initial 7 to 8 hours.
The findings suggest that the risk of an early death increases when sleep times veer from the "ideal" 7 to 8 hours, according to Ferrie -- though, she pointed out that there are people who just naturally sleep more or less than that and have no increased health risks.
"However, for most of us," Ferrie noted, "burning the candle at both ends or sleeping for 9 or more hours is not ideal over prolonged periods in terms of good health."
SOURCE: Sleep, December 1, 2007.