I learned this from a neuro rehab sleep specialist when she presented at our local neuro rehab hospital. She had just attended a nation rehab and sleep conference and learned the latest.

Many studies show the first 24 to 48 hours are much different than after 48 hours. There are many therapies that work in those first 2 days that do not help after.

The key issue is good blood flow in the brain and good glymph drainage. Activity causes blood flow. Proper slow wave sleep causes glymph system drainage. Sleep that does not include REM and slow wave sleep has minimal value as it just lets toxins collect. Daytime sleep is shown to reduce the proper stages of sleep at night. Daytime sleep does not usually include the cycle of sleep stages. The stages are based on sleep within the circadian rhythm sleep pattern that happens at night.

Some of the information about brain function during different stages and types of sleep was not discovered until 2012-2013 when they were able to image the sleeping brain with the detail needed.