How Much Deep Sleep Do You Need?

by Lee A. Surkin, MD, FACC, FCCP, FASNC, FAASM

Deep sleep, also known as slow-wave sleep or the third stage of non-REM sleep (stage N3), is vital for optimal health. It helps in repairing and restoring functions needed for day-to-day life. In short, deep sleep:

• Promotes feeling rested
• Supports memory consolidation
• Heals damaged tissue
• Strengthens the immune system

Due to its importance, a lack of deep sleep can lead to learning difficulties and frequent infections. Not getting enough deep sleep can even contribute to some serious health conditions like heart disease and Alzheimer’s disease.

What is Deep Sleep?

Deep sleep occurs in the third stage of NREM (non-rapid eye movement) sleep. During deep sleep, heart rate, blood pressure, and breathing slow down and brain activity appears in long slow waves, also referred to as delta waves.

In general, people fall into the deep sleep stage an hour after falling asleep. Initial periods of deep sleep are 20 to 40 minutes long, and become progressively shorter as the night wears on. Sleepers are typically hardest to wake up during deep sleep versus REM (rapid eye movement) sleep when they can be fast awakened. If awakened during slow-wave sleep, people experience mental fogginess for up to an hour.

Due to its importance, a lack of deep sleep can lead to learning difficulties and frequent infections. Not getting enough deep sleep can even contribute to some serious health conditions like heart disease and Alzheimer’s disease.

How Much Deep Sleep Do You Need?

When it comes to non-REM, deep sleep versus REM sleep comparison, it is pretty obvious that we spend a lot more time during non-REM sleep – 75%, of which 13 to 23% are in deep sleep, whereas only 25% is spent in REM sleep.

However, our sleep requirements change with age. Precisely speaking, deep sleep reduces with age so a person under the age of 30 may need 2 hours of deep sleep per night, whereas a person over the age of 65 may only need half an hour of deep sleep per night.

What Are the Effects of Lack of Deep Sleep?

Making a difference between lack of deep sleep and sleep deprivation, in general, hasn’t been easy for researchers. Yet, they’ve found the following potential effects of lack of deep sleep:

• Sleep inertia – feeling groggy and disoriented for up to an hour after waking up.
• Impaired memory – forgetfulness and poor retention of memories.
• Higher risk of diabetes – lack of deep sleep reduces insulin sensitivity and leads to an increased risk of diabetes.
• Hypertension – during deep sleep blood pressure reduces and by losing deep sleep the risk of hypertension increases.
• Mood changes – staying positive during the day is difficult without getting the deep sleep needed at night.

Lack of deep sleep could also reduce sleep quality in general, thus leading to other sleep deprivation-related symptoms including:

• Poor focus and concentration
• Mood swings and irritability
• Slower reaction times
• Low energy levels
• Chronic health issues like obesity, depression, and heart disease
• Work, school, or social-life problems

How to Get More Deep Sleep?

Finally, let’s see how you can increase the amount of deep sleep you get each night. Namely, even though there is no single solution to increasing deep sleep, certain steps can help improve your sleep hygiene which in turn would improve sleep quality and promote deep sleep. Here are some tips to follow:

• Do regular exercises – a half-an-hour work out a day, at least three hours before bed, is ideal for improving sleep.
• Don’t consume caffeine or alcohol before bedtime – avoid consuming these stimulants for at least several hours before going to bed.
• Increase sunlight exposure – to keep a healthy sleep schedule exposure to daylight is key, while lowering lights in your home before bed.
• Follow a strict sleep schedule – keeping a consistent schedule, i.e. going to bed and waking up at the same time every day, even during weekends, promotes better sleep.