In all the 100 billion-or-so neurons firing off all day, your brain creates a substantial amount of waste products, including beta amyloid and tau. (You wouldn’t want to be interrupted either.) Well, it turns out that deep sleep is bath time for the brain. Many have questioned why Mother Nature, in her infinite wisdom, would make us so oblivious to the outside world while we’re deep sleeping. Slow-wave sleep also limits cortisol production, which positively impacts insulin levels and blood pressure. Both of these actions stabilize blood sugar and limit fat gain. Growth hormone, for instance, which is elevated in deep sleep, is known to increase insulin sensitivity and muscle mass. There are several reasons why deep sleep is so good for the metabolism. But research has shown that even healthy young people will have metabolic impairment similar to seniors when deep sleep is disturbed. Metabolic diseases (including high blood pressure and diabetes) are usually associated with aging. If our lives were literally on the line each time we plunged into deep sleep, then deep sleep had to be essential. (This means that even loud sounds can’t wake us.) So, it follows that any pre-modern person sleeping in the savanna would have been extremely vulnerable to attacks in their most profound snoozing state… They had to cheat death each night! Humans have an unusually high arousal threshold during deep sleep. To understand how important deep sleep is for your health, first you have to appreciate just how dangerous it used to be.

But the amount of slow-wave sleep declines dramatically with age – and that decline can predict a variety of health issues. You’ll typically spend 60 – 90 minutes in deep sleep each night.

This coincides with a peak in Growth Hormone levels, which promotes tissue repair. Scientists believe that deep sleep (also called slow-wave sleep) is so restorative in part because of the ramped-up ‘rest and digest’ nervous system activity. Even your temperature reaches a daily low.ĭuring this lull, though, your body’s regenerative potential skyrockets. But research suggests that it’s every bit the brain tonic, too.Ĭompared to lighter sleep and REM, deep sleep seems like a dormant phase – your breathing, brain activity, and blood pressure all decrease. Deep sleep is known to be the body’s most rejuvenating sleep stage.

Too much deep sleep