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Overview of sleep disorder

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Sleep disorders (SDs) are among the most common clinical problems encountered in the field of medicine. Approximately, 10% of adults suffer from pronounced insomnia and another 10% from markedly increased daytime sleepiness.1 Sleep disorders cause high socioeconomic burden to the affected individuals due to increased accident risk, sick leave and cardiovascular-related consequences. Nevertheless, the prevalence, burden and management of SDs are often overlooked, which leads to undertreatment of the condition, making it as a serious health concern.

Increased awareness of the disorder, proper understanding of the most common causes in each agegroup along with an effective method of history taking, that is applicable to all agegroups are necessary to diagnose SDs.

Effective therapeutic strategies are available for many SDs. Treatment includes a variety of strategies based on the underlying disorder including lifestyle changes, medications, supportive therapy and the application of continuous positive airway pressure (CPAP) in patients suffering from sleep disordered breathing.


It is essential to know the basics of sleep cycle and the different stages in order to understand the various disorders of sleep. Sleep represents one-third of the human life. It has multiple functions including rest and maintenance of the brain, rest of the cardiovascular system and glucose metabolism balance.

The US National Sleep Foundation recommends 8–9 h of sleep for adults as optimal and that sufficient sleep benefits alertness, memory, problem solving, overall health and reduces the risk of accidents.2 Nevertheless, sleep quality is more important than the total number of hours slept because sleep requirements vary from person to person.

Types and Stages of Sleep

Human sleep is a succession of five stages: four non-rapid eye movement (NREM) stages and one rapid eye movement (REM) stage. Rapid eye movement sleep is marked by extensive physiological changes such as accelerated respiration, increased brain activity, eye movement and muscle relaxation.

The NREM sleep is further divided into four stages. Each stage can last from 5–15 min. A completed cycle of sleep consists of a progression from stages 1–4 before REM sleep is attained, then the cycle starts over again.

Stage 1 (Drowsiness):

  • Transition state between sleep and wakefulness.
  • Eyes begin to roll slightly.
  • Lasts only for a few minutes before moving on to next stage.

Stage 2 (Light sleep):

  • Heart rate slows and body temperature decreases.
  • The body prepares to enter into deep sleep.
  • Only lasts for a few minutes.

Stages 3 and 4 (Deep sleep):

  • Deep sleep stages, with stage 4 being more intense than stage 3.
  • When awakened during this stage of sleep, individuals often feel groggy and disoriented for several minutes.
  • Children may experience bedwetting, night terrors or sleepwalking.

The REM sleep (dream sleep) is characterized by the following:

  • Rapid eye movement along with occasional muscular twitches.
  • Heart rate and respiration increase and become erratic.
  • Intense dreaming occurs as a result of heightened cerebral activity.

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Sleep Cycle

One complete sleep cycle lasts about 90–100 min. Therefore, during an average sleep period, a person will experience 4–5 complete sleep cycles. The first sleep cycles have relatively short REM sleeps and long periods of deep sleep but later in the night, REM periods lengthen and deep sleep time decreases. Therefore, as the night goes on, the dream period becomes longer.

Sleep deprivation, altered sleep timing, change in environment and stress frequently affect the progression of the sleep cycle. Psychological conditions like depression shorten the duration of REM sleep. Further, pharmacological treatment for psychiatric conditions may cause difficulty in sleeping and can inhibit REM sleep stages.

Written by: healthplus24.com team

Date last updated: April 12, 2015