Normal Sleep Cycles For Energy And Mental Clarity

Sleep is essential for the human body and brain. Sleep provides the restorative time needed for the brain and body to rebuild and heal at a cellular level. This can be done since all other functions, except those required for life, are inactive. According to the National Sleep Foundation, there is no specific number of minutes or hours that is required for everyone. In fact, there may be genetic factors that play a major role in the variations that are seen between the amount of sleep that a person needs compared to others. Sleep amounts will vary based on culture as well, which typically has evolved due to environmental factors, hours of daylight and darkness and the development of circadian rhythms based on these factors. 1

Fibromyalgia patients should understand sleep cycles and the role of sleep because fatigue is one of the primary symptoms. Familiarity with the problems associated with lack of quality sleep can help you develop an effective management plan.

There are two different types of sleep measures used by researchers. These include the basal sleep need, which is the basic number of minutes or hours that the individual must have to be able to perform at an optimum level during the waking hours. In addition, individuals also have what is known as a sleep debt, which is actually sleep that is lost because of interruptions, poor health or sleeping at times that are not in synch with the circadian rhythms or the natural sleep patterns of the body.

Sleep Stages

All sleep occurs in cycles. It is not characterized by one long duration level at each of the stages of the cycle either, nor is there one sustained cycle. Why the human body, as well as all mammals and birds require sleep in cycles is not clearly understood. During these cycles an electroencephalogram (EEG) can be used to monitor the level of sleep based on the presence of different types of eye movements and brain activity. There are non-rapid-eye-movements or nonREM as well as rapid eye movements or REM. People of different ages, particularly between children and adults, have different sleep cycles, both which contain nonREM and REM periods. Research indicates that adults need between three to five of these cycles per night with each cycle lasting approximately 90 minutes. The REM activity is different in sleep cycles at the beginning and ending of the sleep period, further contrasting differences in sleep cycles or stages. 2

Non-REM Sleep

Non- REM sleep, sometimes indicated as NREM includes three different sub-stages which occur in a classic pattern. Disruptions of the patterns of light sleep or Non-REM sleep are not as problematic as disruptions of sleep in the deep REM stage. This is why if you have just gone to sleep you can wake up and fall back to sleep relatively easily but if you are in a deep sleep and suddenly aroused you often may have significant difficulty in getting back to sleep.

N1 is the first stage of sleep that allows the brain waves of the waking brain, the alpha waves, to change to a lower frequency known as the theta waves. During this stage of sleep people often drift in or out of sleep and typically have some involuntary muscle movements. These can include jerking of the limbs or head which can be relatively violent or gentle in nature. There is no dreaming in this stage, but people can experience hypnagogic (early sleep) hallucinations, which can be very sensory in nature including hearing, seeing, smelling, tasting and feeling things that are not there.

N2 is the stage where adults spend the greatest amount of sleep time, which is up to about 55% of total sleep minutes. In this stage muscle activity is decreased and the sleeper is not consciously aware of their environment unless they are startled from their sleep.

N3 sleep is characterized as slow-wave sleep where the theta waves still occur but there are approximately 20 % delta waves which range from 0.5 – 2 hertz. At the end of N3, delta waves can increase to 50%. It is during this stage that nightmares, sleepwalking and nocturnal enuresis (urination) occur.

REM Sleep

During REM sleep, which accounts for about one quarter of the total sleep time, the brain and body is working but also rejuvenating. There is muscle atonia (loss of strength) which prevents the larger muscles from moving, allowing the best recovery and repair. It is in this stage that the eyes are moving very rapidly, breathing can increase or decrease based on the response to the deep dreams that are present.

Researchers now believe that REM sleep is the time that the brain is categorizing all the input obtained during the waking hours. This includes consolidating both procedural activities as well as spatial memory. Also, at this time, the brain is determining what information needs to be stored and what information can be discarded and requires no specific categorization.

Often disturbances in REM sleep with no known cause (idiopathic) are linked to the development of specific neurodegenerative disorders. In a study of patients with idiopathic REM sleep disturbances and normal sleeping individuals, it was found that those with interrupted REM sleep had lower attention spans, poorer verbal memory and slower EEG readings during waking hours. 3

Research also links the importance of REM sleep to the consolidation of emotional memories. The researchers compared data and recall of negative emotional memories in groups that had a nap and groups that did not. During the nap the subjects were in REM sleep. Those individuals that napped and those that were in REM sleep longer had higher emotional memory facilitation than those that had lower amounts of REM sleep or those that had no sleep at all. 4

This information may help in understanding why low levels of basal sleep or high sleep debt results in lack of memory and cognitive functioning. It also sheds light on why conditions that deprive individuals of sleep such as insomnia, fibromyalgia and chronic fatigue syndrome are linked to increased problems with attention span, memory recall, learning and mood disorders such as depression and anxiety.


1 How Much Sleep Do We Really Need? (n.d.). Retrieved from National Sleep Foundation:

2 Steiger, A. (2010). Sleep Cycle. In I. B. Weiner, & W. E. Craighead, Corsini Encyclopedia of Psychology. John Wiley & Sons, Inc.

3 Massicotte-Marquez, J., Decary, A., Gagnon, J.-F., et al. (2008). Executive dysfunction and memory impairment in idiopathic REM sleep behavior disorder. Neurology , 1250-1257.

4 Nishida, M., Pearsall, J., & Buckner, R. L. (2008). REM Sleep, Prefrontal Theta, and the Consolidation of Human Emotional Memory. Cerebral Cortex , 1158-1166.

This article was originally published on July 11, 2012 and last revision and update of it was 9/7/2015