Our experience with sleepless nights tells us that getting too little sleep isn't good for us, but oddly enough getting too much sleep can work against you and it can make your memory worse.

A study of 15,000 women found that those who slept seven hours per night had the best memories, while those who slept five hours or less didn’t do as well on memory tests.

“Women who got too little or too much sleep had the memories of women about two years [their senior],” said Elizabeth Devore, ScD, of Brigham and Women’s Hospital in Boston. And that was true for the test subjects in both mid-life and later on.

While Dean M. Hartley, PhD, director of science initiatives at the Alzheimer’s Association, pointed out the study doesn’t necessarily show cause and effect, he said, “Together with its other health benefits, including its role in protecting against heart disease and diabetes, this is yet another reason to get a good night’s sleep.”