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        People may complain of difficulty getting to sleep or staying asleep, intermittent wakefulness during the night, early morning awakening, or combinations of any of these, according to Dr S Sathyanarayanan of Sri Chakra Hospital, Chennai.

        Sleep consists of two distinct states as shown by electroencephalo-graphic studies: (1) REM (rapid eye movement) sleep, also called dream sleep, D state sleep, paradoxic sleep, and (2) NREM (non-REM) sleep, also called S stage sleep, which is divided into stages 1, 2, 3 and 4 and is recognisable by different electro-encephalographic pattern. Stages 3 and 4 are 'delta' sleep. Dreaming occurs mostly in REM and to a lesser extent in NREM sleep.

        Sleep is a cyclic phenomenon, with four or five REM periods during the night accounting for about one-fourth of the total night's sleep (1 Fraction 1/2 - 2 hours). The first REM period occurs about 80-120 minutes after onset of sleep and lasts about 10 minutes. Later REM periods are longer (15-40 minutes) and occur mostly in the last several hours of sleep. Most stage 4 (deepest) sleep occurs in the first several hours.

        Age-related changes in normal sleep include an unchanging percentage of REM sleep and a marked decrease in stage 3 and stage 4 sleep, with an increase in wakeful periods during the night. These normal changes, early bedtimes, and daytime naps play a role in the increased complaints of insomnia in older people.Variations in sleep patterns may be due to circumstances (eg 'jet lag') or to idiosyncratic patterns ('night owls') in persons who perhaps because of different 'biologic rhythms' habitually go to bed late and sleep late in the morning. Creativity and rapidity of response to unfamiliar situations are impaired by loss of sleep. There are also rare individuals who have chronic difficulty in adapting to a 24-hour sleep-wake cycle (desynchronisation sleep disorder), which can be resynchronised by altering exposure to light.

        One of the major sleep disorders is Dyssomnias (Insomnia) Classification and clinical findings Transient episodes are usually of little significance. Stress, caffeine, physical discomfort, daytime napping, and early bedtimes are common factors.

        Psychiatric disorders are often associated with persistent insomnia. Depression is usually associated with fragmented sleep, decreased total sleep time, earlier onset of REM sleep, a shift of REM activity to the first half of the night, and a loss of slow wave sleep - all of which are nonspecific findings. In maniac disorders, sleeplessness is a cardinal feature and an important early sign of impending mania in bipolar cases.

        Abuse of alcohol may cause or be secondary to the sleep disturbance. There is tendency to use alcohol as a means of getting to sleep without realising that it disrupts the normal sleep cycle. Acute alcohol intake produces a decreased sleep latency with reduced REM sleep during the first half of the night.

        Heavy smoking (more than a pack a day) causes difficulty falling asleep - apparently independently of the often associated increase in coffee drinking.

        Sedative-hypnotics - specifically, the benzodiazepines, which are the most commonly prescribed drugs to promote sleep - tend to increase total sleep time, decrease sleep latency, and decrease nocturnal awakening, with variable effects on NREM sleep. Withdrawal causes just the opposite effects.

        Treatment:

        In general, there are two broad classes of treatment for insomnia, and the two may be combined: psychologic (cognitive-behavioural) and pharmacologic. In situations of acute distress, such as grief reaction, pharmacologic measures may be most appropriate.

        Psychologic:

        Psychologic strategies should include educating the patient regarding good sleep hygiene: 1) Go to bed only when sleepy, 2) Use the bed and bedroom only for sleeping and sex, 3) If still awake after 20 minutes, leave the bedroom and only return when sleepy, 4 ) Get up at the same time every morning regardless of the amount of sleep during the night, 5) Discontinue caffeine and nicotine, at lease in the evening if not completely, 6) Establish a daily exercise regimen, 7) Avoid alcohol as it may disrupt continuity of sleep, 8) Limit fluids in the evening and 9) Learn and practise relaxation techniques.

        When the above measures are insufficient, medications may be useful.