It is not known whether or not this increases the risk of heart disease developing later in life, but the snoring and daytime sleepiness can often be eliminated with treatment. Contrary to the personal experience of many people, sleep is not a continuous unchanging state. Through examination of brain wave recordings identical to that obtained as part of the Sleep Heart Health Study, one can see that there are two distinct phases of brain wave activity that occur during sleep. These two types of sleep occur in cycles during the night, although periods of REM sleep are longer during the second half of the night than during the first half. REM sleep received its name because early sleep researchers were able to see rapid eye movements underneath the closed eye lids of sleeping subjects.
Scientists believe that REM sleep is the time when most people dream.
Because when people are awakened during REM sleep, they recall imagery of dreams. REM sleep also is a state of physiologic activation during sleep. During NREM sleep, blood pressure, pulse and respiratory rate generally decrease. However, during REM sleep these indices tend to increase and fluctuate almost as if the individual was awake. In fact, the brain waves during REM sleep resemble that seen when someone is awake.