We’ve talked before about how sleep deprivation causes disease. Now we’ll discuss sleep disorders, or primary issues with abnormal sleep, and their consequences.
Sleepwalking is the act of walking and performing other behaviors while asleep. Automatic, nonconscious routines are executed, like brushing teeth or opening the refrigerator.
Sleepwalking happens during NREM sleep, and not REM dreaming sleep (like some think). Neurologically, sleepwalking is accompanied by an unexpected spike in nervous system activity, causing the person to be stuck somewhere between sleep and wakefulness.
Sleepwalking is more common in children than adults, for unknown reasons - possibly because kids spend more time in NREM sleep than adults do.
In one of the most extreme cases, a sleepwalker drove 14 miles to an in-laws’ home, stabbed the mother-in-law to death, and strangled the father-in-law (who survived). This person was later acquitted as not being control of his actions. This defense has been tried in later cases (most unsuccessfully).
Insomnia is defined as making enough time for sleeping, but having insufficient sleep quantity or quality, for more than 3 months. Symptoms include difficulty falling asleep, waking up in the middle of the night, and feeling unrefreshed in the morning.
When they do sleep, insomniacs have more fragmented REM sleep and shallower brainwaves in NREM.
1 out of 9 people suffers from insomnia. It’s twice as common in women than men, and more common in blacks/Hispanics than whites, for unknown reasons.
The most common triggers of insomnia are emotional concerns or distress. The biological cause is linked to an overactive sympathetic nervous system, which raises body temperature and levels of cortisol/epinephrine. In turn, the thalamus, hippocampus, and amygdala all remain more active than in normal sleeping patients
Given the complex physiology of insomnia, it’s unlikely blunt instruments like sleeping pills will fix the root cause.
People with narcolepsy show sudden bouts of extreme sleepiness during the day. Some people who are chronically sleep-deprived mistakenly think they’re narcoleptic. The severity of feeling for narcolepsy is far more severe, equivalent to the feeling after 3 consecutive all-nighters. Narcolepsy occurs in just 1 out of 2,000 people
Narcoleptics also suffer other symptoms:
How does narcolepsy arise? It’s a disruption in a normal process. Normally, wakefulness is signaled by the neurotransmitter orexin in the hypothalamus; in sleep, this is shut off.
There are no current effective treatments for narcolepsy.
Gravely, sleep deprivation can directly cause death.
In rodent studies, REM sleep deprivation causes death over the same period as food deprivation - about 15 days.
In humans, sleep deprivation leading to death is uncommon (possibly since the natural urge to sleep is so strong). But lack of sleep could contribute to more acute causes of death like seizures, and thus be misreported.
The strongest evidence that humans can die from sleep deprivation comes with a very rare inherited condition, fatal familial insomnia. In this disease, prion proteins cause the thalamus to be destroyed, and the patient is totally unable to sleep, even with heavy sedatives. Severe disability sets in (dementia, speech disorders), and death occurs within 10 months. There are no treatments or preventions.
Let’s return to the question of normal sleep amounts.
On the lower end, you may have seen reports of hunter-gatherer tribes who sleep just 6.5 hours, leading to assertions that this is a universally “natural” state for all humans. They also are rarely obese.
But this is a misguided conclusion. In reality, the hunter-gatherer tribes are basically perpetually starving, since food is never abundant for long periods of time. Starvation naturally induces less sleep, so that animals stay awake longer to search for food. (This also decreases obesity).
To wit, the average life span is just 58 years, much shorter than humans in industrialized societies. In nutrition-rich situations, most humans need 8 hours of sleep.
Can you sleep too much? Some population studies show increased risk of death when sleeping over 9 hours, suggesting sleeping too much might be harmful. But the author argues this data is confounded by infection and cancers in long-sleeping people [though these confounds should already have been controlled for].
* Matthew Walker argues there is no evidence that sleeping more causes any health defects