How Does The Body React To Lack Of Sleep?

Did you know that after a day without sleep you could be similar to someone with high blood alcohol levels? If that isn’t startling enough, there are other bad effects of sleep deprivation.

Your body needs sleep to rest, repair, and refill on energy. So going long stretches without sleep to “get the job done” or “meet a deadline” or while trying to pack too much into your life can take its toll on your body. While for some, this may be unavoidable, the downside of sustained sleep shortfall can be bad enough to merit concern. Sleep deprivation can bring on a number of changes in your body, both subtle and obvious.


The effect of lack of sleep is associated with dipping alertness, poor attention, weakening cognitive performance, and decreased brain function and activity. This can lower productivity at the workplace, endanger your well-being, and even become a safety hazard.

How Much Should You Sleep?

A healthy adult needs 7 to 9 hours of sleep everyday after every 17 to 18 hours.


Going by the National Sleep Foundation’s recommendations for an adult between 26 and 64 years, 7 to 9 hours of sleep every day is a good goal. That said, you could get away with 6 hours of sleep, but no less. The average person needs to get some sleep every 17–18 hours. Any longer without sleep and your body starts to show signs of sleep deprivation.1

The Progressive Decline

To understand the ill effects of staying up that little bit longer, take a look at what happens to your body with each hour of sleep lost.


When You Don’t Sleep For 18–24 hours

This kind of sleep deprivation is fairly common in some professions and even among single parents or working parents who are also primary caregivers for their family.

Sleep deprivation causes a decline in vigilant attention. Your responses slow down, you tend to make errors, and you take longer to do tasks.2


According to one study, subjects who had gone 17 to 19 hours without any sleep showed performance on tests quite like those with blood alcohol levels of 0.05%. These sleep-deprived individuals responded as much as 50% slower on some tests. Their accuracy of responses also took a hit and was significantly worse than what is associated with people with blood alcohol content (BAC) of 0.05%. As the hours without sleep increased, the performance was closer to those with BAC of 0.1%.3

The researchers concluded that sleep is a biological necessity to ensure normal brain function, keep you alert, and maintain normal cognitive performance.4


When You Don’t Sleep For 48 hours

This kind of extended sleep deprivation is not usual for the average person. Those in emergency services or military forces, for instance, may have to go a few days without sleep.

Longer periods of sleep deprivation are believed to impact the immune profile of the body, making you more susceptible to diseases. One study investigated this premise in subjects who went 48 hours without sleep. The body’s natural killer cells (a type of lymphocyte or white blood cell) that are a core part of the human immune system were found to be much lower. This decrease with 48 hours of sleep deprivation could be reversed when subjects went through recovery sleep. However, if this level of sleep loss is sustained for longer spells, it could have a bearing on the body’s ability to fight tumors and viruses.5


With this kind of sleep deprivation, blood pressure and heart rate also rise, putting you at greater risk of a stroke. As one study showed, sleep deprivation causes the body’s diastolic blood pressure to increase and interfere with the autonomic nervous system’s regulation of the cardiovascular system.6

Your body tries to compensate by indulging in microsleeps where it effectively “shuts down” for spells of up to 30 seconds. After each microsleep you return to reality a bit disoriented. This is potentially dangerous if you are driving, handling heavy machinery or hazardous materials, or are in a job that puts people’s lives in your hands. It is impossible to avoid these microsleeps that occur on their own and cannot be consciously overridden by willpower or otherwise.7


72 hours

As time progresses, you will see issues with higher mental processes. Motivation becomes a challenge for many. Perception also gets hampered. Hallucinations are also experienced by some people after staying up three days. Others may create false memories in their minds. Your senses (smell, sight, and even touch) get impacted adversely. Tremors and physical aches and pains also start to set in. And all this in addition to the signs you would have seen after earlier stages of sleep deprivation!8

How Far Can You Push It?

Chronic deprivation messes with the glucose metabolism of the body. Getting under 6.5 hours of sleep every night on a sustained basis could cause your glucose tolerance to drop by 40%. Poor glucose tolerance puts you at higher risk of developing type 2 diabetes. Those with total sleep deprivation fare even worse as the glucose secretion pattern changes completely compared to those experiencing normal nocturnal sleep.9

Deprivation also decreases energy expenditure and interferes with your appetite. Researchers found that people experiencing a regular lack of sleep have a higher body mass index (BMI) than those who get their complete recommended rest. Inadequate sleep causes changes to levels of hormones responsible for controlling hunger. Appetite-reducing leptin levels dropped, and appetite-stimulant ghrelin levels were higher in those who got less sleep. Losing that sleep may actually cause you to crave calorie-rich foods, sweets, carbs, and starchy food, putting you at risk of obesity.10

Sleep deprivation on an ongoing basis can result in long-term ailments and metabolic disorders, costing you time, money, and your health. It may be well worth reorganizing your life so you don’t miss out on this vital restorative time for your body.