Theresa E. Gildner, lead author, doctoral student
, University of Oregon's anthropology department
June 16, 2014 Middle aged or older people who get
six to nine hours of sleep per night think better that those who sleep
fewer or even more hours, report researchers who were looking at cognitive
decline and dementia as people age.
turning to sleep gadgets -- wristbands, sound therapy and
sleep-monitoring smartphone apps -- is a good idea, suggest the
University of Oregon researchers who led this study.
"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
"In all six countries, which are very different
culturally, economically and environmentally - despite all these
differences - you see similar patterns emerging."
They say their study 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.
The study is published in the June issue of the
Journal of Clinical Sleep Medicine.
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
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
"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
Co-authors with Gildner and Snodgrass were: UO
doctoral student Melissa A. Liebert, anthropology; Paul Kowal of the
World Health Organization in Geneva, Switzerland, and University of
Newcastle Research Centre on Gender, Health, and Aging in Australia; and
Dr. Somnath Chatterji of the World Health Organization.
Funding for the joint NIH-WHO agreement comes from
the NIH National Institute on Aging (YA1323-08-CN-0020). An additional
NIH grant (RO1-AG034479) also supports the project, which will continue
to track a variety of changes among the participants over time.
About the University of Oregon
The University of Oregon is among the 108
institutions chosen from 4,633 U.S. universities for top-tier
designation of "Very High Research Activity" in the 2010 Carnegie
Classification of Institutions of Higher Education. The UO also is one
of two Pacific Northwest members of the Association of American
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