SUNDAY, May 1 (HealthDay News) -- For middle-aged adults, sleeping less than six or more than eight hours a night is associated with a decline in brain function, British researchers contend.
The magnitude of that mental decline is equal to being four to seven years older, the researchers said.
"There is an expectation in today's 24-hour-a-day society that people should be able to fit more into their lives," said study author Jane Ferrie, a senior research fellow in the department of epidemiology and public health at University College London Medical School.
"The whole work/life balance struggle is causing people to trade in precious sleeping time to ensure they complete everything they feel is expected of them. Our study suggests that this may have adverse effects on their cognitive function," she said.
In fact, women who slept seven hours per night had the highest score for every cognitive measure, followed by those who had six hours of sleep. For men, cognitive function was similar for those who reported sleeping six, seven or eight hours.
However, less than six hours of sleep -- or more than eight hours -- were associated with lower scores, Ferrie said.
Noting that many biological processes take place at night, Ferrie explained that "sleep provides the body with its daily need for physiological restitution and recovery. While seven hours a night appears to be optimal for the majority of human beings, many people can function perfectly well on regular sleep of less or more hours."
However, since most research has focused on the effects of sleep deprivation on biological systems, it is not yet fully understood why seven hours is optimal -- or why long sleeping appears to be detrimental, Ferrie said.
"Chronic short sleep produces hormones and chemicals in the body which increase the risk of developing heart disease and strokes, and other condit
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