Shorter dream-stage sleep may be related to earlier death – Harvard Health Blog

Time and time again, adequate sleep has been shown to be critical to daily functioning and long-term health. Sleep serves numerous roles: recovering energy for the brain, clearing waste products, and forming memories. Prior studies have clearly linked shortened sleep times to heart disease, obesity, reduced cognitive performance, worsened mood, and even a shorter life. There is now new research that suggests that lack of a certain type of sleep (the dream stage of sleep) may be related to an earlier death in middle-aged and older people.

What is REM sleep?

Normal sleep is broken down into two sleep types: rapid eye movement (REM) and non-rapid eye movement (NREM). NREM is further classified by depth of sleep; N1 and N2 are lighter sleep stages, and N3 is deep sleep, which is most restorative. (REM is the stage where vivid dreaming occurs.) Brainwave activity during this time appears similar to the brain’s activity while awake. REM periods generally occur every 90 minutes, and are longest during the second half of the night. REM sleep normally makes up 20% to 25% of sleep time.

How does sleep change with age?

Sleep time and sleep stages naturally change as we age. Total sleep time decreases by 10 minutes every decade until age 60, when it stops decreasing. Time in N3 sleep, the deepest sleep stage, also shortens with age; time in N1 and N2 tends to increase. As a result, people wake more easily from sleep as they age. The percentage of REM sleep also naturally decreases; thus, reduced time spent in REM may be a marker of aging.

The circadian rhythm is a 24-hour internal clock that governs numerous body functions including body temperature, release of hormones, and sleep time. The internal clock “advances” with age, so older adults

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