Effects of sleep deprivation

Excerpted from  Improving Sleep , Medical Editor: Lawrence Epstein, MD, Instructor in Medicine, Harvard Medical School.

Everyone has a bad night of sleep now and then. But sleep deprivation is another thing entirely. Lack of sufficient sleep, or sleep deprivation, can harm your health and well-being, from weight gain to a heart attack.

Sleep deprivation is generally categorized as either complete or partial, depending on how long and how severe the sleep loss is. Both types can lead to similar mental and physical effects.

Complete sleep deprivation

Complete sleep deprivation means staying awake for an entire night or longer — going without any sleep at all. It happens when you pull an all-nighter. Normally, you’re up for 16 or 17 hours before going to bed. As waking hours extend beyond this point, you first feel tired, then exhausted. Simple tasks that are normally easy start to become difficult.

In fact, a number of studies of hand-eye coordination and reaction time have shown that such sleep deprivation can be as debilitating as intoxication. In one study, 24 hours of wakefulness caused as much impairment as a blood alcohol content of 0.10%.

Sleep deprivation also leaves you prone to dozing off at the wheel and losing your concentration — two potentially dangerous phenomena that play a role in thousands of transportation accidents each year.

When people don’t sleep at all for two to three days, they have difficulty completing tasks that demand a high attention level and often experience mood swings, depression, and increased feelings of tension.

Performance is also highly influenced by fluctuations in circadian rhythms. For example, sleep-deprived people may still function fairly well during the morning and evening. But during the peaks of sleepiness in the afternoon and overnight hours, people often literally cannot stay awake and may fall asleep while standing, sitting, or even while talking on the telephone, working on the computer, or eating.

Partial sleep deprivation

Partial sleep deprivation occurs when you get some sleep, but not 100% of what you need. Doctors refer to this as building up a sleep debt.

After a single night of short sleep, most people function at or near their normal level. They may not feel great, but they can usually get through the day without others noticing that anything is amiss. After two or more nights of short sleep, people usually show signs of irritability and sleepiness. Work performance begins to suffer, particularly on complicated tasks, and people are more likely to complain of headaches, stomach problems, sore joints, memory lapses, and sluggish reaction time. In addition, people face a far higher risk of falling asleep on the job or while driving.

Long-term partial sleep deprivation occurs when someone gets less than the optimal amount of sleep for months or years on end — a common scenario for insomniacs and people with sleep disorders. But even people without specific sleep issues may fall prey to this problem, if they can’t resist the around-the-clock opportunities for online commerce, communication, and entertainment.

Both complete and partial sleep deprivation can harm your health, performance, and safety — sometimes as much as being intoxicated. Fortunately, the effects often improve once you catch up on sleep. But if sleep problems persist, it’s important to work with your doctor to identify the cause and to adopt healthy sleep habits.