No doubt about it: We could all do with a little more restorative sleep. In fact, a study from the National Academy of Medicine reports as many as 50 million to 70 million people in the U.S. suffer from chronic sleep problems, causing daytime drowsiness, poor work and school performance, and a litany of medical problems, including increased risks for high blood pressure, heart attack, and stroke. The Centers for Disease Control and Prevention (CDC) says lack of sleep is a public health problem, with low levels of high-quality, restorative sleep leading to increases in workplace injuries, industrial disasters, and serious auto accidents every day. And that’s just the tip of the iceberg.
Lack of Sleep and Metabolism
More recently, researchers have begun to take a closer look at the link between sleep and metabolism – specifically, metabolism-related diseases and disorders like insulin resistance and type II diabetes. The studies have revealed an interesting if somewhat alarming link among all three that could have far-reaching implications for both short-term and long-term health and even longevity. And it all seems to stem from glucose homeostasis – the delicate balance between how much glucose is produced by the body and how much is used for energy production. To understand this interrelationship, you have to know a little bit about how the body processes glucose, sometimes called “blood sugar.”
Under normal conditions, the body derives glucose from the foods we consume. Glucose, in turn, is converted into a usable form of energy by insulin, a hormone produced by the pancreas. The ability of the body to turn glucose into insulin is referred to as glucose tolerance. Normally, an individual’s glucose tolerance – that is, their ability to turn glucose into energy – fluctuates throughout the day, with highest levels in the morning and lowest levels during the middle of the night when sleep is deepest. In fact, it’s this natural “glucose cycle” that helps keep glucose levels in check. Since glucose control depends on a normal sleep-wake cycle, it makes sense interruptions in this cycle would have an impact on glucose tolerance. And that’s the next issue researchers set out to explore.
Sleep, Glucose Levels, and Diabetes
In one seminal study, scientists set out to compare glucose levels in people who had normal sleep and those who were sleep deprived. Both groups of study participants received continuous infusions of glucose to eliminate potential fluctuations that could occur as a result of differences in glucose production. What they found was that people in the sleep-deprived group, blood glucose levels increased far less during the first half of sleep, and the decrease in glucose levels that typically occurs during early morning hours was much steeper among those who had no sleep compared to those who had normal sleep. In essence, that meant sleep-deprived patients had a “glucose deficit” compared to those with normal sleep. What’s more, as the day wore on, glucose levels continued to be abnormal compared to the typical glucose cycle; those in the sleep-deprived group experienced higher glucose levels in the afternoon despite the fact their insulin levels remained the same, suggesting insulin action was also impaired.
Of course, there’s a difference between being acutely sleep deprived and having chronically poor sleep habits, like restless nights or poor quality of sleep. To recreate those experiences, researchers conducted studies using partial sleep deprivation. In one study conducted by researchers from the University of Chicago, study participants were subjected to six consecutive nights of 4-hour sleep. Then, the same participants had seven consecutive nights of 12-hour sleep. All participants consumed the same diet during the study period to provide consistent results. Blood tests were performed throughout both periods to measure glucose tolerance levels, then the results of both groups were compared.
At the end of the study, the researchers found glucose tolerance levels were significantly impaired, with sleep deprivation causing low glucose tolerance rates similar to those of people with glucose intolerance and type-2 diabetes. After the full sleep period of the study, glucose tolerance rates returned to normal. Based on these findings, the researchers concluded that even a single week of poor sleep resulted in physiological changes associated with the development of type 2 diabetes.
And finally, a second study looked at glucose tolerance and insulin resistance in “short sleepers,” people who habitually sleep for less than 6.5 hours per night, comparing the results with people who slept about eight hours each night.1 The researchers found that while glucose tolerance was similar in both groups, the short-sleepers secreted about 50% more insulin, making them much more likely to develop insulin resistance and potentially type 2 diabetes.
Improve Sleep Quality to Reduce Your Own Risks
The take-home message from these studies is clear: To minimize the risks of insulin resistance, type 2 diabetes, and obesity, it’s essential to improve your own personal sleep habits. Lots of factors can contribute to a lack of sleep and poor quality sleep, and the good news is, most of them are modifiable:
- Diet: When it comes to sleep, it’s not just what you eat, but when you eat that counts. A bedtime snack might sound great, but if heavy meals can keep you awake and some foods are more likely to cause acid reflux when you’re lying down. If you must have a snack, keep it small and simple, and try not to eat right before slipping under the covers.
- Environment: Even a tiny amount of light can trigger a reduction in melatonin, a chemical produced during sleep. Installing heavy curtains and even wearing a sleep mask can help keep light out so sleep is deeper and more restful. Cooler temperatures are also important for good sleep.
- Sleep apnea: This chronic condition occurs when the tissues at the back of the throat relax and descend into the airway, partially obstructing breathing. These tiny interruptions in respiration can occur hundreds of times per night, interfering with deep sleep even though you may not realize it.
- Snoring: Although it’s a common side effect of apnea, snoring also can be caused by other issues like allergies, sinus problems, and defective nasal passageways. Plus, snoring doesn’t just affect your own sleep – it affects just about anyone else in the vicinity as well.
An occasional sleepless night usually is nothing to worry about, but when lack of sleep becomes chronic, it can become a serious medical problem that warrants prompt attention. If you’re suffering from a lack of sleep or poor quality of sleep, talk to your doctor. Not only will you feel better, but you can decrease serious medical risks that could take a significant toll on your health and your quality of life.
- Mander BA, Colecchia E, Spiegel KS, Van Cauter E. Short Sleep: a risk factor for insulin resistance and obesity. Sleep. 2001;24 (supplement):A74–75.