People have long wondered why we need to sleep. Why can’t we just stay awake all of the time? What purpose does sleep serve? These might seem like silly questions because sleep obviously makes us less tired (or should, when we get enough of it!), but there’s clearly more to it – we regularly need sleep whether we’ve been working hard all day, or just relaxing. Over the last few years, several papers have been published that have given us a better understanding of what happens to us while we sleep, and why getting sleep is so important to us biologically. A lot of this research has shown that, interestingly, when we sleep our brain performs important “housekeeping” chores and helps maintain normal metabolic functions.
In October 2013, a paper was published showing that, during sleep in mice, bodily fluids help clear out buildups of Β-amyloid in the brain. How did the brain accomplish this, and what does it mean exactly? The researchers found that channels between the brain’s neurons (the interstitial space) increase in size by 60% when mice sleep, and interstitial fluid (fluid that’s normally all around our body’s cells) is flushed in. This influx of fluid washes out Β-amyloid, a peptide that’s associated with Alzheimer’s disease. (Similarly, a study in 2010 showed that chronic sleep loss can lead to significant decreases in task performance.) It’d be interesting to see if studies can show a correlation between sleep deprivation and occurrence of Alzheimer’s disease in patients. Either way, the study shows an interesting correlation, and makes me want to get more sleep to help clean out my brain!
Another interesting connection has been made between sleep and how the body digests food. In 2012, a paper was published showing that sleep deprivation, along with disruption of a person’s normal circadian (sleep/wake) cycle, disrupts normal metabolic function. Specifically, under these conditions, researchers found that after eating a meal the insulin secretion from the pancreas was likely inadequate, which likely led to observed increased blood glucose concentrations. Consequently, the researchers speculated that sleep deprivation may increase risk of metabolic disorders such as obesity and diabetes. Similarly, just last month a paper was published showing that the nerves in a person’s stomach, in correlation to the body’s circadian clock, work to regulate when we eat.
So as more research on sleep is being published, more and more reasons why it’s important to get a good night’s sleep are emerging — potential decreased risks of Alzheimer’s disease and metabolic disorders are more than enough encouragement for me to try and catch enough z’s.
For further reading:
- Lulu Xie et al.’s article “Sleep Drives Metabolite Clearance from the Adult Brain” in Science
- Science’s article “Sleep: The Brain’s Housekeeper?”
- Science’s article “To Sleep, Perchance to Clean”
- DA Cohen et al.’s article “Uncovering residual effects of chronic sleep loss on human performance“
- Orfeu M. Buxton et al.’s article “Adverse Metabolic Consequences in Humans of Prolonged Sleep Restriction Combined with Circadian Disruption” in Science
- ScienceDaily’s article “Stomach ‘Clock’ Tells Us How Much to Eat”
- Teisha J. Rowland’s book Biology Bytes: Digestible Essays on Stem Cells and Modern Medicine