Everyone has to sleep. So it is not surprising that everyone has thoughts about sleep. However the science of sleep suggests that not all of these beliefs are correct. Here are some common myths about sleep in our culture, in no particular order:
It is dangerous to wake a sleepwalker. Contrary to popular belief, sleepwalking does not occur during REM sleep and seems to be unconnected to dreaming. Muscles are actively paralyzed during REM sleep, so it is unlikely that sleep walkers are acting out dreams. Instead, sleepwalking tends to occur during the first third of the night, during deep non-REM sleep. This is possible, as walking is a reflex that does not necessitate involvement of the brain. Many cultures have sayings to suggest that sleepwalkers won’t hurt themselves if they are just left alone. But this is not the case and serious accidents such as falling down stairs are not uncommon.
More REM sleep is always better. While quality of sleep matters and while deeper sleep stages tend to be experienced as more refreshing, this is not the case for REM sleep. REM sleep is defined by EEG patterns that are hard to distinguish from those experienced in the waking state. In fact, excessive REM sleep is a hallmark of depression and characteristically non-refreshing.
People – particularly great people like Napoleon – really only need to sleep 4 hours a night. Sleep needs are highly idiosyncratic. Some people need to sleep more, others less and this seems to be mostly determined by genetics. Most people are well rested if they sleep 7-8 hours in a 24-hour period. While people with lower intrinsic sleep needs obviously have more time at their disposal, it is most critical how this time is put to use. Importantly, there is no evidence that Napoleon had diminished sleep needs, as he napped quite a bit. Modern people trying to imitate Napoleon’s habit in order to achieve greatness tend to commit atrocious errors of judgment, due to chronic lack of sleep.
The natural state of sleep is to sleep “as needed” or in multiple chunks. This is an increasingly popular notion, but entirely without empirical support. Importantly, it doesn’t even make sense conceptually. Whatever the function of sleep is, it likely evolved to match the fluctuating energy levels reaching the earth from the sun throughout the day. Most animals and people entrain to the sun-cycle, either in a diurnal (sleeping at night) or a nocturnal (sleeping during the day) fashion in order to conserve energy, avoid predators and the like.
Alcohol (a “nightcap”) will help you to sleep better. Ethanol is a nervous system depressant, so it is possible that it will knock you out, but this state should not be confused with actual sleep. Put differently, alcohol typically induces low-quality sleep that doesn’t exhibit natural sleep architecture and is much less refreshing. Worse, physiological effects from metabolizing the alcohol such as dehydration have a high likelihood of waking the sleeper in the middle of the night, disturbing sleep further. This is – by the way – also why sleeping pills should not be taken lightly or chronically. They tend to induce a state that behaviorally looks like sleep, but is not comparable to actual sleep in physiological terms.
Bedwetting as a child is a telltale sign that the person is a psychopath. In the 1960s, it was believed that this is the case, along with childhood fire starting and cruelty to animals. However, research since then has shown bedwetting (enuresis) to be extremely common in children and mostly due to developmental delays. If there is a link between bedwetting and later maladjusted behavior, it seems to be due to stress or trauma, which makes bedwetting more likely.
Sleep problems are rare. While sleep is undervalued in our society and no one really wants to talk about it, there is no question that a lot of people have issues with sleep. Experts estimate the number of people with sleep problems in the US to be between 60 and 70 million, or about 1 in 5 people. So if you have a problem with sleep, it is likely that you are in good company.
Sleep deprivation is just making you a little tired. Lack of sleep affects all aspects of brain function and behavior. Importantly, it affects judgment and reaction time. Lack of sleep is implicated in hundreds of thousands of accidents a year.
Tryptophan from the turkey puts you to sleep after the Thanksgiving meal. This classic sounds neurosciency, but is not true. First of all, turkey has no more tryptophan than other meat like chicken. Second, the tryptophan competes with other amino acids in the turkey protein for access to the brain, specifically phenylalanine, tyrosine, leucine, isoleucine and valine. Third, the reason why tryptophan is associated with sleep is because it is metabolized into melatonin, but this takes quite a while.
Older people need less sleep. Not quite. It seems that way because it is more fractured, but careful studies suggest that the overall sleep time is the same, just distributed throughout the day, for unknown reasons. If anything, sleep quality is changing – both the amount of REM sleep and the amount of deep sleep is decreasing with increasing age.