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Sleep quality, duration important for cognition in aging adults

Recent data suggest that achieving 6 to 9 hours of sleep per night may help maintain cognition in middle-aged and older adults.

“We wanted to look at aging, particularly dementia and cognitive decline as people get older, and the importance of sleep,” Theresa E. Gildner, a doctoral student in the department of anthropology at the University of Oregon in Eugene, said in a press release. “Our results provide compelling evidence that sleep matters a lot. In all six countries, which are very different culturally, economically and environmentally — despite all these differences — you see patterns emerging.”

Gildner and colleagues evaluated data for 34,203 adults aged 50 years and older from the WHO’s Study on global AGEing and adult health (SAGE) to determine the effect of sleep duration and quality on cognition. Participants were from six middle-income countries, including China, Ghana, India, the Russian Federation, South Africa and Mexico. Similar samples of adults aged 18 to 49 years were also drawn for comparison purposes.

In all countries, except Russia and Mexico, women reported significantly longer average durations of sleep compared with men (P<.001). South Africa had the longest reported sleep durations among both men and women (P<.001), while India had the shortest reported sleep durations (P<.001).

Compared with all countries, Mexico had the highest reported sleep quality (P<.001). In all countries, women reported lower sleep quality compared with men (P<.05).

Higher cognition scores were found among men compared with women in all countries (P<.001), except Russia (P=.09) and Mexico (P=.22). Participants who slept less than 6 hours per night (short sleep duration) had lower cognitive scores compared with those who achieved intermediate sleep (more than 6 to 9 hours; P<.001). Compared with intermediate sleep duration, those who slept more than 9 hours had lower cognitive scores (P<.001).

“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,” study researcher J. Josh Snodgrass, PhD, of the department of anthropology at the University of Oregon, said. “Sleep is something that is important but often undervalued in our society. From doing this research and being familiar with the literature 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 the associations between sleep and health issues.”

Disclosure: The study was funded in part by the NIH’s National Institute on Aging Interagency Agreement with WHO and the NIH. The researchers report no relevant financial disclosures.