"When the day is long... And the night, the night is yours alone" to sleep a full 7-8 hours! Although it may seem like your body ‘shuts down’ during sleep, it is an active time for your brain and many physiological processes. During sleep, your brain goes through different stages, with some lighter stages of sleep (referred to as stages 1 and 2), and some deeper stages of sleep (stages 3 and 4). There is also a fifth stage of sleep known as rapid eye movement sleep, or REM sleep. It is during this stage that your heart rate increases, your breathing becomes more irregular and dreams are most likely to occur.
A normal night-time sleep period occurs in cycles of approximately 90 minutes. The duration of sleep stages within each cycle changes throughout the night and varies person to person. Typically, a sleep cycle will begin with a period of non-REM sleep followed by a very short period of REM sleep. The duration of REM sleep increases with the cycles while you are sleeping. Throughout a full night's rest, the average person will spend 20-25% of their sleep in REM.
REM sleep is the restorative part of our sleep cycle. It is very important for emotion regulation and memory and is also the peak of protein synthesis at the cellular level, which keeps many processes in the body working properly. Decreased sleep duration interferes primarily with REM sleep and dreaming since the body devotes deeper non-REM sleep to shorter hours of sleep. A recent study has shown that REM sleep loss is associated with increased inflammatory responses, increased risk for obesity, and memory problems.