Sleep is a natural periodic state of rest for the mind and body, in which the eyes usually close and consciousness is completely or partially lost from which a person can be aroused. Historically, sleep was thought to be a passive state. However, sleep is now known to be a dynamic process, and our brains are active during sleep. Sleep affects our physical and mental health, and is essential for the normal functioning of all the systems of our body.
The International Classification of Sleep Disorders lists more than 80 different sleep disorders.
Prevalence of insomnia which is difficulty in getting sleep is around 6% to 15% in the population.
Sleep apnea syndrome (sudden stoppage of breathing for few seconds), often associated with insomnia or daytime sleepiness, is found in approximately 2% to 4% of the general population.
Restless legs syndrome (urge to move the legs, to get relief of abnormal sensation) is present in approximately 6% of the general population with a higher prevalence in the elderly subject.
Parasomnias are a category of sleep disorders that involve abnormal movements, behaviors, emotions, perceptions, and dreams that occur while falling asleep, sleeping, between sleep stages, or during arousal from sleep. Most parasomnias are dissociated sleep states which are partial arousals during the transitions between wakefulness and NREM sleep, or wakefulness and REM sleep. Parasomnias are less studied in the general population; prevalence of several parasomnias remains unknown. Some NREM parasomnias (sleep-walking, night-terrors, and confusional arousal) are common during childhood but decrease in frequency with increasing age
Nocturnal terrors, confusional arousals and nightmares have been observed with prevalence ranging from 2.2% to 5%. Despite their high frequency, sleep disorders remain poorly identified; less than 20% of individuals with sleep disorders are correctly diagnosed and treated
Narcolepsy also known as hypnolepsy, is a chronic neurological disorder caused by the brain's inability to regulate sleep-wake cycles normally. People with narcolepsy often experience disturbed nocturnal sleep and an abnormal daytime sleep pattern, which often is confused with insomnia. Narcoleptics, when falling asleep, generally experience the REM stage of sleep within 5 minutes, while most people do not experience REM sleep until an hour or so later
Facilities for PSG, CPAP titration, MSLT, MWT and SIT
Polysomnography (PSG): Also known as a sleep study, is a multi-parametric test used in the study of sleep and as a diagnostic tool in sleep medicine. Polysomnography is a comprehensive recording of the biophysiological changes that occur during sleep. It is usually performed at night. The PSG monitors many body functions including brain (EEG), eye movements (EOG), muscle activity or skeletal muscle activation (EMG) ,heart rhythm (ECG), respiratory airflow and respiratory effort indicators and peripheral pulse oximetry during sleep.
CPAP titration: CPAP stands for continuous positive airway pressure, and a CPAP titration study is the process that a health facility goes through to fit someone with sleep apnea with a CPAP machine. The CPAP machine is a small pump that pumps room air through a mask and into the nasal passages of a person with sleep apnea, and this opens up the breathing pathways to allow for a deeper sleep
MSLT: The Multiple Sleep Latency Test (MSLT) is a sleep disorder diagnostic tool. It is used to measure the time elapsed from the start of a daytime nap period to the first signs of sleep, called sleep latency. The test is based on the idea that the sleepier people are, the faster they will fall asleep.
The MSLT can be used to test for narcolepsy, to distinguish between physical tiredness and true excessive daytime sleepiness
MWT: In contrast to the MSLT, which measures a subject's ability to fall asleep, the maintenance of wakefulness test (MWT) measures a subject's ability to stay awake in a quiet, non-stimulating situation for a given period of time
SIT: Suggested Immobilization Test (SIT) is conducted in the evening prior to diagnostic polysomnography (sleep study). The SIT uses rest duration to provoke symptoms of restless legs.