A new study finds that the less older adults sleep, the faster their brains age.

Results show that each hour of reduced sleep duration changed the annual expansion rate of the ventricles by 0.59 percent. Ventricles are the internal chambers of the brain. Their expansion is a reliable marker for the risk of cognitive impairment. The study also found that reduced sleep sped up the annual decline rate in cognitive performance by 0.67 percent.

“Our findings relate short sleep to a marker of brain aging,” said lead author Dr. June Lo in a Duke-NUS press release.

“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,” added senior author Professor Michael Chee. He is director of the Centre for Cognitive Neuroscience at Duke-NUS. “In coming years we hope to determine what’s good for cardio-metabolic and long term brain health too,”

The study examined the data of 66 older Chinese adults, from the Singapore-Longitudinal Aging Brain Study. 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.

According to the authors it remains to be investigated if sleep duration plays a more important role in predicting brain and cognitive aging in less healthy older adults.