Maybe turning to sleep gadgets --
wristbands, sound therapy and sleep-monitoring smartphone apps -- is a good
idea. A new University of Oregon-led study of middle-aged or older people who
get six to nine hours of sleep a night think better than those sleeping fewer
or more hours.
The
study, published in the June issue of the Journal of Clinical Sleep Medicine,
reaffirms numerous small-scale studies in the United States, Western Europe and
Japan, but it does so using data compiled across six middle-income nations and
involving more than 30,000 subjects for a long-term project that began in 2007.
"We
wanted to look at aging, particularly dementia and cognitive decline as people
get older, and the importance of sleep. Our results provide compelling evidence
that sleep matters a lot," said lead author Theresa E. Gildner, a doctoral
student in the UO's anthropology department. "In all six countries, which
are very different culturally, economically and environmentally -- despite all
these differences -- you see similar patterns emerging."
The
study, based on the first wave of data from a continuing long-term project,
focuses on people 50 years old and older in China, Ghana, India, Mexico, the
Russian Federation and South Africa. Among the key findings were:
·
Men
reported higher sleep quality than women in all six nations, with men and women
in Mexico reporting the highest.
·
Women
reported longer sleep durations than men in all countries except Russia and
Mexico. Men and women in South Africa slept longer than in any other country.
The least sleep hours for both sexes occurred in India.
·
Individuals
sleeping less than six hours and more than nine hours had significantly lower
cognitive scores compared to those in the intermediate group.
Trained
native speakers in each country interviewed the participants, who rated their
sleep quality on a five-point scale and the number of hours they'd slept over
the two previous nights. That information was averaged. Participants then went
through five standard cognitive tests involving immediate recall of a list of
presented words, delayed recall of those words later, forward and backward
recall of long lists of numbers, and a verbal fluency test in which they listed
as many animals as possible without repetition, the use of proper nouns or
descriptors.
The
study concludes that the findings have important implications for future
intervention strategies for dementia. The consistent associations between
intermediate sleep durations, high sleep quality and enhanced cognitive
performance in these diverse populations suggests that improving sleep patterns
may help reduce the level of cognitive decline as seen in older adults.
Another
important finding, Gildner said, is the gender difference in all sleep and
cognition variables. Citing previous studies, the authors hypothesized that
women's sleep patterns reflect postmenopausal changes, increased bladder
instability and feelings of isolation after the loss of a spouse or lack of
social support. Cognition scores of women may result from their sleep
difficulties and/or lower educational levels.
The
growing database in the long-term study, known as the Study on global AGEing
and adult health (SAGE), is allowing researchers to mine many combinations of
variables connected to health and lifestyle, said J. Josh Snodgrass, professor
of anthropology at the UO. "It also will allow anthropologists to explore
cultural factors that may contribute to sleeping and health patterns."
Snodgrass
is a key investigator on SAGE, which is funded by a joint agreement of the
National Institutes of Health and the World Health Organization.
"This
study is hugely powerful and so different from what's been done in the past,
simply because of the consistency of how the data was collected --
multi-national, random samples of people," he said. "Sleep is something
that is important but often undervalued in our society.
"From
doing this research and being familiar with the literature," he added,
"an emphasis on sleep issues by the media in recent years is warranted.
Every single piece of evidence that people look at now as they are
investigating sleep and different health associations is all showing that sleep
really, really, really matters. We're just now scratching the surface on what
patterns of sleep normally are, and also what are these associations between
sleep and health issues."
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