Less-Than-Optimal Sleep May 'Age' the Brain05/02/11
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
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
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 conditions like high blood pressure and cholesterol, diabetes and obesity," she added.
The report was published in the May 1 issue of
Ferrie's team collected data on 5,431 men and women, aged 35 to
55 in 1985, who took part in a long-term look at London-based
office staff known as the Whitehall II study.
In 1997-1999, the participants were asked how many hours they
slept on an average week night, and were asked the same question in
2003-2004 after an average 5.4 years of follow-up. Those who
reported changes in their sleep patterns were then compared with
people whose sleep duration stayed the same over the course of the
In 2003-2004, each individual was given a battery of standard
tests to assess his or her memory, reasoning, vocabulary, global
cognitive status and verbal fluency.
The researchers found that during the study, 58 percent of men
and 50 percent of women continued to sleep the same amount each
night. However, 7.4 percent of women and 8.6 percent of men
increased their slumber from seven to eight hours per night.
This change in sleep pattern was associated with lower scores on
six tests of cognitive function, compared with people whose sleep
time did not change, the researchers found.
Only scores on the test of short-term verbal memory were not
affected by sleeping more, they noted.
In addition, some 25 percent of women and 18 percent of men
reported decreases in their sleep -- dozing less than six, seven or
eight hours per night.
This change was associated with lower scores on three of the six
cognitive tests, with lower scores on the reasoning, vocabulary and
global cognitive status tests, the researchers said. Surprisingly,
increasing sleep from six hours or less had no beneficial effect,
Dr. Alberto Ramos, co-director of the Health Sleep Medicine
Program and an assistant professor of clinical neurology at the
University of Miami Miller School of Medicine, said various studies
have shown sleeping too little or too much increases the risk of
dying, having a heart attack or stroke and other health
"Getting enough sleep helps many brain functions," Ramos said. "It is restorative, it lets you concentrate better and process new information better and faster."
It is not clear why too much sleep may be unhealthy, Ramos said.
However, he speculates, it may be a sign of other health
Ramos added that to stay healthy, sleep is as important as
eating well and being physically active.
"We have to think of sleep the same way as we think about diet and exercise," Ramos said. "If we want to have a healthy lifestyle we think of diet and exercise, but part of the equation is that good sleep should be part of having a healthy lifestyle for healthy aging."
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