By Dr. Mercola
According to the Centers for Disease Control and Prevention, lack of sleep is a public health epidemic, noting that insufficient sleep has been linked to a wide variety of health problems.
After reviewing more than 300 studies to determine how many hours of sleep most people need to maintain their health, an expert panel concluded that, as a general rule, most adults need right around eight hours per night.
Unfortunately, an estimated 40 percent of Americans are sleep deprived.
Many get less than five hours of sleep per night, which can have a wide range of health repercussions, from an increased risk of accidents, weight gain and chronic diseases, to reduced sex drive, and decreased sexual satisfaction.1
It also plays an important part in memory formation, and sleep dysfunctions such as sleep apnea have been shown to speed up memory loss.
I used to be one of those people who disregarded the value of sleep, rarely getting more than five or six hours of sleep each night.
I typically average between 8 ½ to 8 ¾ every night, now that I more fully appreciate sleep's massive value for overall health and longevity.
Sleep and Memory Formation
In the featured video,2 Robert Stickgold, director of the Center for Sleep and Cognition at Beth Israel Deaconess Medical Center, discusses some of the lesser known reasons for why we need to sleep.3
Sleep is actually essential not just for cementing events into long-term memory, but also for making sense of your life.
According to Stickgold, during sleep your brain "extracts the gist of what happened" to you during the day, and fosters insight into the workings of your life.
Essentially, during sleep, your brain pulls together and extracts meaning, while discarding unimportant details. In fact, sleep increases your ability to gain insights that would otherwise remain elusive by about 250 percent!
Dreaming plays a role in this process too. One test showed that thinking about correctly navigating through a maze really had no effect on performance.
Ditto for taking a nap during which no dreaming was reported. Dreaming about navigating through the maze however, increased performance 10-fold!
According to Stickgold, the act of dreaming acts like a predictive marker, indicating that your brain is doing what it needs to do to successfully accomplish the task at hand.
These types of tests also showed that in the dream state, your brain is processing information at multiple levels. Your whole brain is engaged. So, during sleep, part of your brain is busy stabilizing, enhancing, and integrating new memories. It's also extracting rules, and the "gist" of what's going on.
Then, during dreaming, old and new memories are integrated to form a new whole, and possible futures are imagined. This is what you actually perceive as "the action" of your dream. The sum total of these processes then allows you to see the meaning of your life.
Less Sleep Results in Greater Calorie Consumption While Awake
On a more physical level, getting less than seven hours of sleep per night has been shown to raise your risk of weight gain, by increasing levels of appetite-inducing hormones.
Recent research4 in which people's sleep and food intake was carefully tracked confirmed that more sleep correlated with fewer calories consumed, and vice versa.
Most participants spread their eating and drinking over the course of 15 hours each day. About 25 percent of their daily calories were consumed before noon, and more than 35 percent after 6 pm.
This kind of eating pattern is, I believe, a major reason why so many Americans struggle with their weight. They're grazing all day long, and eating a majority of their food far too close to bedtime.
This flies in the face of our genetic ancestry, as our bodies are not designed to continuously receive calories. In fact, a number of beneficial effects take place when you go for periods of time without eating. This includes improved insulin and leptin sensitivity, which plays an important role in weight and health.
Eating too close to bedtime also disrupts the function of your mitochondria, thereby speeding up cell damage and contributing to DNA mutations. Indeed, the benefits of restricting your eating to a narrower window each day are revealed in this study too.
As reported by Reuters:5
"The researchers also tested whether the app might help people eat less by encouraging them to consume food and drink over a shorter stretch of the day.
They asked eight overweight people who tended to eat over more than 14 hours of the day to cut back to 10 to 11 hours. After 16 weeks, these people lost about 3.5 percent of their excess body weight and reported sleeping better..."
Poor Sleep Raises Risk of Accidents and Depression
Getting less than six hours of sleep leaves you cognitively impaired, which can have repercussions both at home, at work, and on the road. In 2013, drowsy drivers caused 72,000 car accidents in which 800 Americans were killed, and 44,000 were injured.6
Even a single night of sleeping only four to six hours can impact your ability to think clearly the next day. Lack of sleep has also been firmly linked to a heightened risk for depression.
Of the approximately 18 million Americans with depression, more than half of them struggle with insomnia. While it was long thought that insomnia was a symptom of depression, it now seems that insomnia may precede depression in some cases.7
Research has also found that sleep therapy resulted in remarkable improvements in depressed patients. About 70 percent of those with sleep apnea, whose sleep is repeatedly disrupted throughout the night, also tend to suffer from symptoms of depression.8
It's interesting to consider that if lack of sleep and lack of dreaming prevents you from seeing the meaning of your life, and prevents you from integrating memories and imagining possible futures (as discussed in the featured video), couldn't that play a significant role in fostering depression? I believe it could.
Long-Term Sleep Deprivation Is a Risk Factor in Many Chronic Diseases
Over the long term, sleep deprivation — regardless of the cause — has been linked to a number of serious health effects, including but not limited to:
- Diabetes. One of the most recent studies9 on this linked "excessive daytime sleepiness" with a 56 percent increased risk for type 2 diabetes
- Decreased immune function. One recent study10 suggests deep sleep plays a role in strengthening immunological memories of previously encountered pathogens in a way similar to psychological long-term memory retention. In this way, your immune system is able to mount a much faster and more effective response when an antigen is encountered a second time
- Cardiovascular and heart disease. In one study, women who got less than four hours of shut-eye per night doubled their risk of dying from heart disease.11 In a more recent study,12 adults who slept less than five hours a night had 50 percent more coronary calcium, a sign of oncoming heart disease, than those who regularly got seven hours.
Interestingly, sleeping more than nine hours a night was associated with 70 percent more calcium in the coronary arteries, compared to sleeping seven hours. The quality of sleep also had a big impact on blood vessel health. Those who reported sleeping poorly had 20 percent more arterial calcium than those who slept well.
- Alzheimer's.13 A number of studies have linked poor sleep or lack of sleep to an increased risk of Alzheimer's. One of the reasons for this has to do with the fact that the glymphatic system — your brain's waste removal system — only operates during deep sleep. Researchers have discovered14 that your blood-brain barrier tends to become more permeable with age, allowing more toxins to enter.
This, in conjunction with reduced efficiency of the glymphatic system due to lack of sleep, allows for more rapid damage to occur in your brain and this deterioration is thought to play a significant role in the development of Alzheimer's.
- Cancer. Tumors grow two to three times faster in laboratory animals with severe sleep dysfunctions. The primary mechanism thought to be responsible for this effect is disrupted melatonin production, a hormone with both antioxidant and anti-cancer activity. Melatonin both inhibits the proliferation of cancer cells and triggers cancer cell apoptosis (self-destruction). It also interferes with the new blood supply tumors required for their rapid growth (angiogenesis). A number of studies have shown that night shift workers are at heightened risk of cancer for this reason.
To Optimize Your Sleep, Stay in Sync with Nature
Download Interview Transcript
One of the key foundational components of sleeping well is maintaining a natural rhythm of exposure to sunlight during the day and darkness at night. This was addressed in a previous interview with researcher Dan Pardi, which I've included again for your convenience. In it, he explains how exposure to bright daylight serves as the major synchronizer of your master clock, which in turn synchronizes all the other biological clocks throughout your body.
If your master clock is "off," it will tend to ripple throughout your system. One reason why so many people get so little sleep, and/or such poor sleep, can be traced back to a master clock disruption caused by spending their days indoors, shielded from bright daylight, and then spending their evenings in too-bright artificial light. As a result, their body clocks get out of sync with the natural rhythm of daylight and nighttime darkness, and when that happens, restorative sleep becomes elusive.
To help your circadian system reset itself, make sure to get at least 10 to 15 minutes of morning sunlight. This will send a strong message to your internal clock that day has arrived, making it less likely to be confused by weaker light signals later on. Also aim for 30 to 60 minutes of outdoor light exposure in the middle of the day, in order to "anchor" your master clock rhythm. The ideal time to go outdoors is right around solar noon but any time during daylight hours is useful.
A gadget that can be helpful in instances when you, for some reason, cannot get outside during the day is a blue-light emitter. Philips makes one called goLITE BLU.15 It's a small light therapy device you can keep on your desk. Use it twice a day for about 15 minutes to help you anchor your circadian rhythm if you can't get outdoors.
The advice to get in sync with nature is echoed in recent research,16 which found that being in close proximity to nature helped improve the sleep quality of seniors. Natural surroundings that had this effect included beaches and parks. Interestingly, this link was much stronger for men than for women, although the reason for this difference could not be discerned. According to study author Diana Grigsby-Toussaint, a professor of Kinesiology and Community health at the University of Illinois:
"Studies show that inadequate sleep is associated with declines in mental and physical health, reduced cognitive function, and increased obesity. This new study shows that exposure to a natural environment may help people get the sleep they need."