Sleep plays an essential part in maintaining health. There are several disorders and disturbances that affect the duration and depth of sleep. In adequate sleep or over sleep can cause numerous behavioral and cognitive problems. Some of the sleep disturbances include:-

Insomnia

This is the commonest sleep disorder. This usually means the inability to initiate or maintain continuous sleep.

Insomnia affects nearly 40% of women and 30% of men. It affects over 50% of people over the age of 65. Insomnia may be loss of quantity (number of hours) and/or quality (depth) of sleep.

In the elderly insomnia may be due to frequent arousals and reversal of sleeping hours from night to day.

Insomnia may be caused by three important factors:-

• Psychophysiologic factors – resulting from age, stress and emotional changes. Psychophysiological insomnia is commonly seen when the patient worries excessively about his/her inability to sleep all night and increases the risk of a sleepless night. There is usually resultant short sleep time, daytime fatigue, and irritability.
• Organic factors – loss of sleep due to other diseases and disorders like heart disease, asthma, snoring, obstructive sleep apnea etc. Other medical disorders include those that cause pain like arthritis, peptic ulcers, and parkinsonism.
• Psychiatric disorders – loss of sleep due to presence of psychiatric problems like depression, anxiety disorders, bipolar disorder etc.

Insomnia can manifest in several ways. Some may suffer from transient insomnia that usually lasts just a few nights. This is commonly caused by an emotional change, stress, anxiety, shift work or jet lag etc.

Chronic insomnia lasts longer than a month. The symptoms of insomnia rarely require confirmed diagnosis. Acute insomnia generally does not require a sleep study for confirmed diagnosis.

In cases where insomnia is present for at least 6 months and there is no response to behavioral, medical, or psychiatric treatment, a sleep study is needed.

Excessive Sleepiness

While insomnia is a common form of sleep disturbance, excessive sleepiness especially during daytime is another common complaint in sleep clinics.

The causes include sleep apnea, narcolepsy or disorders of the nerves including head injury, myotonic dystrophy, Parkinson’s disease, Alzheimer’s disease, postviral infection and developmental disorders.

Parasomnias like sleep-walking, talking in sleep, grinding teeth while sleeping (bruxism) may also result in day time sleepiness.

For diagnosis of these conditions the multiple sleep latency test (MSLT) is employed along with polysomnogram to check for adequacy and pattern of sleep the night before. History from the bed partner or family is also important.

Obstructive sleep apnea

This type of disorder occurs when there is complete or partial obstruction of the upper airway. This may be of varying severity ranging from snoring to severe obstruction and arousal from sleep. This leads to interrupted sleep and day time sleepiness.

Narcolepsy

Narcolepsy occurs in young adults in their second to third decades of life. It affects men and women equally. There is excessive daytime sleepiness, paralysis of the muscles during sleep, hallucinations during sleep and cataplexy (abnormal movements, emotional changes etc.). The patient may be awake but be completely paralyzed - unable to move and experience hallucinations.

Circadian Rhythm Sleep Disorders

These are problems that are associated with timing of sleep and wakefulness. The human body has its own clock called the circadian rhythm. This resides in the suprachiasmatic nucleus (SCN). This clock regulates the sleep and wake rhythms of the body. Types of circadian rhythm sleep disorders include:-

• Delayed sleep phase disorder – this is seen when a person regularly goes to sleep and wakes up more than two hours later than is considered normal. Those who typically sleep late at night (or early next day e.g. 3 AM) and wake up late in the morning or noon are said to have this condition.
• Advanced sleep phase disorder – this is the opposite of delayed sleep phase disorder when a person goes to sleep several hours earlier than normal. The person may go to sleep between 6 to 9 PM and wake up between 2 to 5 AM.
• Jet lag disorder – this occurs when a person travels from one time zone to another. In this new location the person needs to sleep or wake at different times from what his or her body clock is used to. The problem is more severe if more number of time zones are crossed. Jet lag affects all age groups but elderly tend to suffer more than the young adults.
• Shift work disorder - shift work disorder is seen in persons who work on night shifts. While the person may feel sleepy during his or her shift, trying to sleep during the day when off duty is a challenge. Rotating shifts also compound the problem of sleep deprivation.
• Irregular sleep-wake rhythm – this occurs when a person has too many nap times in their 24 hours cycle and do not have a complete restful all-night sleep. There may be insomnia as well as excessive sleepiness.
• Free-running sleep disorder – this is seen when there are variable sleep-wake cycles that tend to shift to a later time every day. Occasionally, the disorder is associated with mental retardation or dementia.