Scientists agree that sleep is essential to health, and while stages 1 to 4 and REM sleep are all important, deep sleep is the most essential of all for feeling rested and staying healthy. The average healthy adult gets roughly 1 to 2 hours of deep sleep per 8 hours of nightly sleep.

What happens if you get no deep sleep?

Summary. Deep sleep, also called NREM Stage 3 sleep, is the deepest stage of sleep. This sleep stage is important for repairing the body and clearing waste from the brain. Lack of deep sleep may harm your immune system, and can increase the risk for dementia and chronic diseases like cancer.

How many hours of deep sleep do you need?

So how much deep sleep do you need? According to New Health Advisor, adults 18 and older need anywhere from 1.5-1.8 hours of deep sleep per night, which is about 20% of your overall sleep. Some people, however, may find they need more hours of sleep in order to feel fully rested and consider it a good night's sleep.