To keep your brain sharp, a new study finds that the sleep sweet spot is seven hours, no more, no less.

Seven hours of sleep a night optimal for memory
Sleep counts: keep your memory sharp with seven hours of sleep daily. Image: DNF-Style Photography/

The Nurses’ Health study, using data from some 15,000 women, found subjects who slept five hours or less on average per day had lower scores on standard memory tests than those who slept seven hours, reports Elizabeth Devore, ScD, of Brigham and Women’s Hospital in Boston.

Women who slumbered for nine or more hours on average also performed worse on memory tests than those who slept seven hours a night. Devore noted that the link between sleep duration and memory held true both in mid-life and later life.

Initial findings were presented in Vancouver at the Alzheimer’s Association International Conference.

Devore also cited mounting research linking sleep deprivation, less than seven hours a night, to an increased risk of heart disease and type 2 diabetes.

At a major sleep conference in Boston this year, researchers from the University of California Berkeley showed that sleep deprivation could also impair a person’s ability to make wise food choices after taking MRI scans of their participants.

Sleep deprivation significantly impairs brain activity in the frontal lobe, a region that controls behavior and is activated when making complex choices, including food selection, the researchers explained.