Amount of Sleep Needed | Health Blog

Date: 03/10/2015    Written by: Beth Levine

Sleep and Stroke Risk

Amount of Sleep Needed | Health Blog

We all know how important it is to get sufficient sleep, and how awful we feel when we don't. Adequate amounts of restful sleep help us perform optimally during the day and contribute to our overall health. Yet most of us constantly bemoan the fact that we just can't find enough time to get the sleep we need. After all, sleeping for eight-and-a-half or nine hours a night practically sounds decadent. And if you could regularly get that kind of sleep, you would probably reap some significant health benefits, right? Not necessarily. In the case of stroke, at least, new research points to a higher risk in adults who sleep the most.

The study, which was conducted at the University of Cambridge in England, found that people who typically sleep for longer than eight hours each night may have an elevated stroke risk compared to those who generally get less sleep.1 The subjects were nearly 9,700 men and women taking part in the European Prospective Investigation into Cancer Study--Norfolk cohort. They were between the ages of 42 and 81 at the outset of the trial and were tracked for close to 10 years. The participants provided information on their sleep habits early in the study, from 1998 to 2000, then were interviewed again four years later to report on their sleep quality and duration at that point. The scientists also logged any occurrences of stroke among the volunteers during the decade-long research.

The majority of the subjects, approximately 70 percent, said that they generally slept between six and eight hours per night. Only 10 percent reported sleeping more than eight hours most nights, and a very small percentage typically slept less than six hours a night. By the end of the study period, 346 of the participants had suffered a stroke.

After analyzing the data, the scientists determined that the individuals who tended to sleep more than eight hours nightly had a 46 percent greater risk of stroke than those who slept six to eight hours. Those who slept the least, averaging less than six hours a night, also faced a greater stroke risk than those in the six-to-eight category, but their risk was increased by only 18 percent, which is considerably better than those who slept the most. However, because there were so few volunteers who fell into the group that slept less than six hours, the evidence of that link is somewhat more tenuous.

There was no positive correlation to consistently being a "long sleeper," reporting eight hours or more in both the initial and follow-up segments of the research, either. The subjects who slept more than eight hours in both time periods were found to have twice the stroke risk of their peers who slept six to eight hours. But a change in sleeping habits was even worse. Those who went from a typical sleeping schedule of less than six hours nightly to requiring in excess of eight hours a night had approximately four times the risk of suffering a stroke than did those who remained in the six-to-eight hours group throughout.

The study was not designed to prove cause and effect, but only demonstrate an association between sleep duration and stroke risk. This leaves open several possibilities. It may be that too much sleep disrupts some function in the brain that increases the likelihood of stroke. There is also a chance that changes have taken place in the brain that result in greater sleep requirements as well as the occurrence of a stroke. Hopefully there will be research that can shed some light on this eventually.

In the meantime, if you tend to sleep for only slightly more than eight hours a night, it's probably not worth cutting back if you do not have other stroke risk factors. We do want to meet our requirements for health reasons, as a 2003 study at the University of Michigan School of Medicine in Ann Arbor found that getting enough sleep is essential to the immune system and the prevention of inflammation.2 If, however, you usually need considerably more than eight hours of sleep to feel refreshed, you might want to examine what might be causing this situation. The need for excessive sleep may be linked to depression, dementia, or a thyroid condition. Also, as we've discussed previously, studies have shown that those who sleep more than eight hours a night have a 12-percent increased mortality rate, and that risk escalates with each additional hour of sleep. For more information on the importance of getting the right amount of sleep and natural ways to sleep better, check out Jon Barron's To Sleep Perchance To Dream.

  • 1. Doheny, Kathleen. "Sleeping too much could raise risk of stroke." CBS News. 26 February 2015. Accessed 1 March 2015. http://www.cbsnews.com/news/sleeping-too-much-could-raise-risk-of-stroke
  • 2. Opp, MR and Toth, LA. "Neural-immune interactions in the regulation of sleep." Frontiers in Bioscience. May 2003. Accessed 2 March 2015. http://www.ncbi.nlm.nih.gov/pubmed/12700057?dopt=Abstract

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