A recent report from the Harvard Nurses’ Health Study suggests that their may be a sweet spot we should be aiming for when it comes to how much sleep we get. As many have long suspected, too little sleep can degrade our mental performance, both in the long term as well as the short term. But evidence now supports the theory that too much sleep can have just as harmful consequences as too little.
A group of women taking part in this study were interviewed about their sleeping habits in 1986, again in 2000, and then three more times over a later 6 year period when they were questioned about their memory and thinking skills. It was found that those women getting five hours or less sleep each night, or nine or more hours were far more likely to test poorly on brain functioning and memory tests. Those that that got a regular seven to eight hours each night, performed the best. The findings of the study were published in the online Journal of the American Geriatrics Society.
It’s important to note that this study does not definitely prove that a lack or surplus of sleep can cause memory and other cognitive problems, it can only form a link. However, the results do fall in line with the larger body of work already published on the issue. For instance, we know that poor sleepers have a higher risk of heart disease and stroke, high blood pressure, type 2 diabetes, and narrowed blood vessels. All of these factors can decrease blood flow in the brain, depriving it of the oxygen and sugar it needs in high quantities to function at an optimum level.
Tests on sleep deprived lab mice show high deposits of the protein ‘beta amyloid’ in their brains. This protein has been linked to cognitive decline in humans for both memory and executive function, and has also been flagged as a potential indication for the development of dementia.
While the study points identifies 7-8 hours as the optimum amount of sleep for the average person, it should be noted that this is recognized at the amount of quality sleep that one should strive for. Those individuals who sleep more than 8 hours per day, typically do so because they fail to achieve an adequate level of quality sleep. They drift in an out of sleep, often being woken during the night. For those individuals, a better regimen of sleep hygiene is recommended before resorting to pharmaceutical solutions to assist their problem.