Zombies do not sleep. Their circadian clock is always in the day phase, making it practically impossible to fall asleep during the night, thus insomnia. It's clear that most zombies have no need for sleep, or they can stay awake for quite a long period, unlike ordinary human beings.

Scientists have tried to figure out why humans and animals sleep. It could restore their brain and heart hormone levels, conserve energy, and for safety purposes.

According to the zombies' metabolism, they may not require to conserve energy. In humans, lack of sleep for a long period can impair cognitive ability.

Still, since zombies' cognitive abilities are already damaged, lack of sleep has no impact on their damaged cognitive ability.

If you have watched, The Night of the Living Dead, then we can excuse you for the idea that zombies are nocturnal creatures that roam all night searching for people to eat their brains.

Besides, if you think zombies will fall asleep during the day and won't attack their prey, you're cheating yourself.

For your information, zombies can be active 24/7, either during the night or day. Although they are not nocturnal beings, their conditions can be described as insomniacs, meaning they stay for a long time without sleep.

Remember the zombification process? When a zombie bites a human being searching for the flesh, the victim's cognitive brain undergoes permanent damage. The internal body clock, the circadian clock, is one of those brain portions that undergo such permanent damage.

A zombie's circadian clock doesn't tick anymore. Hence a zombie is always in the day state, making it practically possible for a zombie to stay awake for a long period.

Why Zombies Don't Need Sleep

Here are several theories explaining why a zombie doesn't need sleep.

The Energy Conservation theory

Whenever an individual sleeps, they conserve energy through reduced metabolism. This allows a person to save energy which can be utilized later during the day. However, this theory doesn't seem to pertain well to zombies since they are already dead people with no metabolism.

Typically, their lack of metabolism is a good reason to say that zombies do not need to conserve energy during the night hence no need to sleep.

The Inactivity Theory

This theory suggests that an individual is inactive during the night to reduce the chances of attack from dangerous animals.

Since a zombie can attack even those dangerous animals, it means it won't have to worry about predators attacking it at night. A zombie staying awake overnight is motivated by the fact it fears being attacked while sleeping. 

The Restoration Theory

It suggests that when a person sleeps, their body undergoes self-restoration and repair. Zombies do not need to restore and repair their constantly decaying bodies.

Zombies don't have living cells that wound attempt the restoration work. The above theories are good reasons why animals, humans included, need to sleep but not zombies.

Types Of Zombies

Let's discuss each type of zombie for a better understanding of why zombies do not require sleeping.

Zombies can arise from 3 different ways based on different folklore:

• Chemical

• Disease

• Mystical

Both the disease and chemical hatched zombies are typically human beings with normal needs.

Still, the outside agent has damaged some brain sections, leaving the primitive part of the brain the main functioning part. They place food as a priority over other survival needs, including sleep.

According to the film, 28 Days Later, zombies that don't feed themselves eventually become weak and die.

Although the film doesn't show that if a zombie doesn't take water, it will eventually dehydrate within 1 -4 days just like ordinary people and, as a result, weaken and die within a week.

Since these zombies are typically human beings with ordinary needs, they will need sleep. Still, the illness or the chemical exposure has deactivated the brain's part that triggers the body to feel the need for sleep. 

Mystical zombies are the reanimated dead people. It means that they are already dead people who have returned to life or remembrance of it. This means that their sustenance needs are already lost.

Their greed for human flesh is powered because they want to spread the virus to other humans, although they have no consciousness of understanding their actions.

Although they will eat the human flesh until their tummies burst open, they aren't feeding to fuel their activities. You will find out the zombies have not slept for several days, yet they are still very active.