In recent years we’ve become much more aware of how sleep, both quality and quantity, can affect our health. Approximately 40% of Americans get less than 7 hours of sleep, which is less than the recommended amount. But as we’ll see here, excessive sleep may be bad for your health.
Insufficient sleep is associated with increased risks for obesity, diabetes, and cardiovascular disease. Keep in mind that this is an association, and causation hasn’t been proven.
Short sleep duration is associated with decreased levels of the satiety hormone leptin, as well as with increased body mass index, so this gives us some reason to think that a causal mechanism between sleep and obesity exists.
Yet some sleep experts question whether the link between sleep and obesity is all that important. Sleep scientist James Horne points out that the link exists mainly with very short sleep duration, 5 hours or less, and that any obesity that may appear as a result takes many years to develop. While inadequate sleep does predispose to metabolic problems like glucose intolerance, this is mainly associated with sleep of less than 4 hours a night, which hardly anyone can sustain for more than a few days.
The real health problem caused by too little sleep, according to Horne, is increased risk of accidents. He believes that sleep debt is something of an urban myth, and that 7 to 7.5 hours is all the sleep most people need. More than that amount is excessive sleep.
Reinforcing Horne’s statements about sleep is another noted sleep researcher, Dr. Daniel Kripke, a psychiatrist who has made his life work studying sleep. He and colleagues studied a very large cohort of 1.1 million people who were part of the Cancer Prevention Study of the American Cancer Society. They found that the lowest mortality rate was associated with 7 hours of sleep, but the real bombshell was as follows:
Participants who reported sleeping 8 hours or more experienced significantly increased mortality hazard, as did those who slept 6 hours or less. The increased risk exceeded 15% for those reporting more than 8.5 hours sleep or less than 3.5 or 4.5 hours.
Let that sink in: more than 8 hours of sleep was associated with significantly increased risk of death, and those who sleep more than 8.5 hours had a 15% greater risk of death, the same as if they slept only 4.5 hours or less per night. This sheds a new light on the amount of sleep we need, and casts some doubt on the idea of a widespread sleep deficit.
Furthermore, Kripke and colleagues importantly found that:
In contrast, reports of “insomnia” were not associated with excess mortality hazard.
Kripke has elsewhere stated that insomnia, for most people, is something that one should not worry about, that it is more an annoyance than anything.
Kripke and his colleagues have also found in several studies that even a brief use of sleeping pills, as little as a few times a year, is associated with greatly increased risk of mortality. Every class of sleeping pill that was examined showed increased risk, which leads one to speculate whether that risk was not due to the type of drug used, but rather to increased sleep alone.
Receiving hypnotic prescriptions was associated with greater than threefold increased hazards of death even when prescribed <18 pills/year. This association held in separate analyses for several commonly used hypnotics and for newer shorter-acting drugs. Control of selective prescription of hypnotics for patients in poor health did not explain the observed excess mortality.
More sleep = more death? If this were not the case, then we would expect different kinds of sleeping pills to have more or less risk, or some might not even have any risk. Yet the association holds even for sedative antihistamines (such as diphenhydramine, the most common over-the-counter sleep aid), so this leads one to think that the common denominator in the link between sleeping pills and death might be excessive sleep itself.
Just to add to the list of woes associated with too much sleep, long sleep duration, greater than 10 hours, is independently associated with persistence of depression and anxiety. And importantly, insomnia was not so associated, while sleep of less than 6 hours was. But the odds ratio for long sleep was much higher, 2.52, than that for short sleep, at 1.49. Does depression affect sleep, or does sleep cause depression?
A topic I’ve covered a fair amount on this blog is sleep deprivation for depression, which still strikes me as the most amazing thing every time I read about it. In a nutshell, depriving depressed people of sleep results in a literally instant cure for depression in up to 80% of patients. This result is no fluke and has been repeated in multiple studies over and over again. So fundamental a process this is that it was discovered in 1818 by Johann Christian August Heinroth, who wrote about it in the first ever textbook of psychiatry.
Medical researchers soon discovered that only one-half night of sleep deprivation gave virtually the same benefits, and was far more tolerable for patients. And deprivation in the latter half works better. Typically, the patient goes to bed at the usual hour and then is awakened, or wakes himself, after 4 hours of sleep, and then stays awake until the following night.
The main problem with this therapy is the possibility of relapse; most depressed patients become depressed again after sleeping, and since this can’t be avoided, it’s a problem. However, sleep phase advance preserved the sleep deprivation cure in over 60% of patients. The addition of light therapy makes the treatment even more effective.
Does the fact that sleep deprivation cures depression have larger significance? We saw above that long sleep duration is strongly associated with depression and anxiety. Could it be that sleeping more than necessary, that is excessive sleep, leads to depression, and that depriving ourselves of sleep cures it? Could it be that sleeping a bit too much each night, say one-half hour more, ultimately leads to depression? Here we tread beyond the scientific facts, but I don’t doubt it. It’s worth considering whether you sleep too much.
Be very skeptical of the mainstream warnings that we all need more sleep. Most of us don’t. Lots of evidence points to sleeping too much as a cause of illness, depression, and even death.
Insomnia is not a cause for alarm. Excessive sleep may be damaging to your health.
If you have trouble with mood and energy levels, try shaving off some of your sleep time. If you normally sleep 8 hours, for instance, try 7.5 or even 7 for a week and see if you don’t feel better. Remember that the lowest mortality rate is associated with 7 hours of sleep.
A good night’s sleep is important for health. But food is also, and just as with food, we can overdo sleep.