Deep sleep, also known as slow-wave sleep or the third stage of sleep, is essential for optimal health. It helps in repairing and restoring functions needed for day-to-day life. This level of sleep:
- Promotes feeling rested
- Supports memory consolidation
- Heals damaged tissue
- Strengthens the immune system
Therefore, a lack of deep sleep can lead to somnolence (sleepiness), memory loss, learning difficulties and even 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 about an hour after falling asleep. Initial periods of deep sleep are approximately 20 to 40 minutes long and become progressively shorter during the night. Most individuals are typically the hardest to wake up during deep sleep vs REM (rapid eye movement) sleep when they can be awakened more rapidly. If awakened during slow-wave sleep, people can experience slow mental processes for up to an hour.
Deep Sleep Requirements
The normal individual adult spends much more time in 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. 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
Conclusion – Better Quality Sleep
Finally, let’s see how we can increase the amount of deep sleep we get each night. Namely, even though there is no single solution to increasing deep sleep, certain steps can help improve sleep hygiene which in turn would improve sleep quality and promote deep sleep. Here are a few 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 a couple of 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.
