The findings could have important implications for the rise of dementia among the elderly, researchers said.

Past research has examined the impact of sleep duration on cognitive functions in older adults.

Though faster brain ventricle enlargement is a marker for cognitive decline and the development of neurodegenerative diseases such as Alzheimer's, the effects of sleep on this marker have never been measured.

Researchers at Duke-NUS Graduate Medical School Singapore (Duke-NUS) examined the data of 66 older Chinese adults, from the Singapore-Longitudinal Ageing Brain Study.

The study started in 2005 and followed a cohort of healthy adults of Chinese ethnicity aged 55 years and above.

Participants underwent structural MRI brain scans measuring brain volume and neuropsychological assessments testing cognitive function every two years.

Additionally, their sleep duration was recorded through a questionnaire. Those who slept fewer hours showed evidence of faster ventricle enlargement and decline in cognitive performance.

"Our findings relate short sleep to a marker of brain ageing," said Dr June Lo, the lead author and a Duke-NUS Research fellow.

"Work done elsewhere suggests that seven hours a day for adults seems to be the sweet spot for optimal performance on computer based cognitive tests. In coming years we hope to determine what's good for cardio-metabolic and long term brain health too," added Professor Michael Chee, senior author and Director of the Centre for Cognitive Neuroscience at Duke-NUS.

The research was published in the journal SLEEP.


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