Deep Sleep or slow wave sleep (SWS)

Do you remember the last time you woke up in the morning feeling quite refreshed and full of energy? You probably you had plenty of deep sleep, also called slow wave sleep (SWS), a time when your brain winds down and takes it easy. If you look at a figure of your brain waves on an electroencephalogram (EEG) as you go though SWS, you would see slow,  tall and rolling waves called delta waves. This is in contrast to the fast waves you see during wake. There are 4 stages of sleep: 1, 2, 3 and REM. SWS defines stage 3.

It is more difficult to wake someone from SWS. This is why children can sleep through a noisy house- they spend a great deal of their sleep in SWS but also their deep sleep is even deeper than adult.  If you wake someone from this stage versus other stages, they are more likely to be groggy and remain so for several minutes. Slow wave sleep tends to occur predominantly in the first half of the night.

If you go for a couple of nights on very little sleep and end up sleep deprived, your body and brain is now craving sleep. So when you finally go to sleep, you will have what is called rebound SWS- it means you get more of it than you normally would. Your brain is trying to make up rest.

Deep sleep occurs not as a result of absence of stimulating activities in the brain. Rather, there are cells in the back of the brain in an area called the brainstem that sends signals to the front part of the brain to actively decrease the activity. It is not a passive rather than an active process.

Slow wave sleep has a special hormonal function. It allows the release of human growth hormone (GH). Children are especially in need for this hormone because it helps them grow.  Not getting a good night sleep might affect their height and strength. Children and young adults have lots of slow wave sleep. But it decreases with age and so elderly have little of it.

Certain sleep disorders tend to occur during deep sleep. Sleep walking occurs out of this stage in some people.

 How to increase deep sleep

  • Increasing your body temperature or heating your body increases deep sleep. So taking a warm shower in the evening or close to bedtime helps.
  • Exercise is another way to increase deep sleep through increasing body heat. In a 1981 study published in the December issue of Science, a significant increase in total sleep time and slow wave sleep was found after a group of individuals completed a 92-kilometer race. This study supports that hypothesis that sleep has a restorative function.
  • Reduce stress. Meditation and deep breathing improves your sleep quality and increase deep sleep. When you are anxious and stressed, deep sleep becomes disrupted and decreases.
  • Medical conditions such as sleep apnea, insomnia, leg jerks or pain can reduce deep sleep. It is important to address them. Talk to your doctor. You might need s a sleep study.
  • Certain medications such as benzodiazepines (clonazepam) reduce deep sleep. Talk to your doctor if you want to change the medication.
  • Few medications can actually increase deep sleep. A couple of those are gabapentin and pregabalin.