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Not getting enough sleep can take real amounts of time off your life. The link between sleep deprivation and mortality has been shown in a wide body of rigorous scientific research. Sleep is essential for survival. Studies in animals have demonstrated that going without any sleep will eventually be, over a period of days or weeks, lethal.
And studies in people have established the association between short sleeping and an increased risk of death. For example, a review of research published in the journal Sleep found an average of a 12 percent higher risk of dying among short sleepers. Short sleepers were people sleeping less than 7 hours a night—in many studies sleeping less than 5.
(We’re talking about sleep deprivation today. But I can’t move on from mentioning this research review above without noting that it also found sleeping too much associated with a higher risk of dying—a whopping 30 percent increase. I’ll come back to this topic of excessive sleeping again. It’s an important one. In the meantime, here’s an article I wrote about the risks of oversleeping.)
And a 12 percent average increase to risk means, of course, that some individual studies found the risk of early death associated with short sleep to be even higher—like this study, which analyzed the connection over a 22-year period in more than 21,000 twins, and found increases in mortality of 26 percent for men, and 21 percent for women.
The big question is: Why? Scientists have a well-established association between lack of sleep and risks of early death. But what is the cause underlying this association? That’s a powerfully important question with huge implications for treating sleep disorders and other health problems.
There’s not likely to be a simple answer, or a single route or mechanism that connects short sleep to mortality risk. That’s because sleep is connected to so much else that the body does—from metabolism to brain function to immunity. Poor sleep is a factor in the chronic, age-related diseases of our time, including diabetes, cardiovascular disease, cancer, and neurodegenerative disorders such as Alzheimer’s.
New research out of Harvard Medical School contains some potentially game-changing information about one particular pathway by which sleep deprivation causes death. It’s a path you’ve heard me talk about before in relation to sleep.
The GUT.
I’ve written a number of times about the sleep-gut connection and its widespread influence over health issues such as weight and metabolism, immunity, and stress. Recently, I talked about how prebiotic foods can help improve gut health, resulting in reduced stress and more time spent in deep and restorative stages of slow-wave and REM sleep.
You’re probably familiar at this point with how the health of your gut contributes to your overall health and well-being. Your intestines are home to the largest concentration of micro-organisms that make up what scientists call the “microbiome.”
How the Gut Microbiome Relates to Sleep
The human microbiome is made up of trillions of tiny microbes. Many are bacteria, but there are also viruses, fungi, and protozoa. These microbial organisms live all throughout the body, but the single largest microbial ecosystem is in the intestines.
The collection of organisms within the microbiome—both the types and amounts of different bacteria and other microbes—has broad effects on mental and physical health, influencing mood, metabolism, cardiovascular and circulatory health, as well as the immune system, and our risk for chronic disease.
The gut microbiome is frequently called our “second brain.” That’s because the gut is home to a nervous system and about 100 million neurons. The nervous system of the microbiome is in constant communication with the brain and our central nervous system, helping to regulate hormone production, immune system function, appetite, digestion and metabolism, mood, and stress responses.
On the sleep front, the microbiome produces some of the body’s melatonin (which is also produced in the brain) as well as other hormones and neurotransmitters involved with sleep, including dopamine, serotonin, and GABA.
Our microbiome is regulated by circadian rhythms. Research has shown that when circadian rhythms are disrupted, the health and functioning of the microbiome suffers. At the same time, so is sleep. The health of the microbiome can also be disrupted by poor diet, stress, illness, and excessive use of some medications including antibiotics.
We know from recent research that:
Irregular sleep schedules can disrupt a healthy gut. This recent study in the journal Nature reveals the connections between sleep, circadian biorhythms, and the gut microbiome. It points to a regular sleep routine as one way to protect and promote optimal gut and immune system functioning. Sticking to a sleep routine, limiting nighttime light exposure, managing stress, and practicing healthy, sleep-friendly eating habits are all ways to keep your circadian clock—and your gut microbiome—functioning optimally.
A couple of nights of poor sleep can harm your microbiome. The relationship between sleep and the microbiome is a two-way street. Our microbiota affects how we sleep. In turn, sleep and circadian rhythms affect the health and diversity of the influential microbial ecosystem that lives in our gut. Recent research shows that not sleeping enough can quickly have a negative effect on microbiome health. After only two nights of partial sleep deprivation, European scientists who conducted this 2016 study found:
- A significant drop in beneficial bacteria
- Changes to the composition of micro-organisms in the microbiome that are linked specifically to obesity and type 2 diabetes
- A significant reduction in insulin sensitivity
Restless, poor quality sleep affects the microbiome AND metabolic health. People who experience sleep disorders, particularly obstructive sleep apnea, often contend with this type of poor sleep quality, which keeps them from spending sufficient time in the most restorative stages of deep sleep and REM sleep.
We know fragmented sleep leads to changes in metabolism and eating patterns that increase risks for obesity and other metabolic disorders, including type 2 diabetes. In the past several years, we’ve also seen a growing body of evidence that dysfunction in the microbiome is a significant factor driving the metabolic changes that lead to obesity and other metabolic disorders. Recent research suggests that fragmented sleep may play an important role in the microbiome-driven effects on metabolic health, in part by triggering inflammation that leads to metabolic dysfunction.
