Want an excuse to sleep in this weekend? Check out this study from the Duke-NUS Graduate Medical School Singapore that says sleeping less may speed up the aging of the brain. The study took place over several years and looked at the structural MRI brain scans of 66 Chinese seniors.

Brain scans are useful when studying cognitive decline because they can measure the speed of brain ventricle enlargement. According to the researchers, “Faster brain ventricle enlargement is a marker for cognitive decline and the development of neurodegenerative diseases such as Alzheimer’s.” In addition to the brain scans, the subjects also had a neuropsychological assessment every two years to check their cognitive function.

The study showed that “each hour of reduced sleep duration at baseline augmented the annual expansion rate of the ventricles by 0.59%, and the annual decline rate in global cognitive performance by 0.67%... after controlling for the effects of age, sex, education and body mass index.”

So what is the optimal amount of sleep? According to Professor Michael Chee of Duke-NUS, “7 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.”

It’s important to note that the study only looked at the effects of low-sleep on cognition in older adults, so it’s hard to say if the brain of a 30 year old who gets less than optimal sleep will age faster. Hopefully, further longitudinal studies will shed more light on this and the many factors that affect aging.