Dealing with abnormal sleep patterns
Dr Zenobia Zaiwalla looks at what lies behind a good – and a bad – night's sleep
What's in this article
lThe significance of rapid eye movement and non-REM sleep
lSleep problems in babies and children and treatment
lEffect of circadian rhythms; the role of genes and external factors
lSleep and age
lRestless leg syndrome
lManaging daytime sleepiness
Sleep medicine is a relatively young field in the UK, with only a couple of centres until the 1980s. In the last decade a number of centres have sprouted, often led by chest physicians and ENT surgeons with an interest in obstructive sleep apnoea, forcing neurologists and neurophysiologists to wake up and contribute to the non-respiratory aspect of this neglected subject.
The two states of sleep
Within sleep, two states are recognised – non rapid eye movement (NREM) and rapid eye movement (REM). These alternate cyclically through the night with cycle time of 90 minutes (50-60 minutes in the newborn). NREM sleep evolved with the homeothermic state and is divided into four stages: stages 1 and 2 (considered light sleep), and stages 3 and 4 (deep sleep with high arousal threshold).
REM is ontogenically primitive with EEG activity closer to wake state, intermittent bursts of REMs and muscle atonia interrupted by phasic bursts producing asynchronous twitching. The atonia of REM sleep prevents acting out of dreams and is lost in REM behaviour disorder when dreams content becomes violent and patients act out their dream, often resulting in injury.
REM behaviour disorder can be a precursor of neurodegenerative disease including Parkinsons. Dream content (pleasant/unpleasant) will be remembered on waking from REM sleep but there is often little or no memory of the preceding mental activity on arousals from NREM sleep, even when associated with complex behaviours and autonomic disturbance as occurs in night terrors or sleep walking.
In the newborn 50 per cent of total sleep time is occupied by REM sleep, progressively shrinking to 25 per cent in the adult, the first block of REM sleep occurring about 90 minutes after sleep onset. Abrupt withdrawal of alcohol and many centrally acting recreational and non-recreational drugs can cause REM sleep to occur at sleep onset. This can also increase total REM sleep, leading to intense vivid often frightening dreams (hypnogogic – sleep onset/hypnopompic or, on waking, hallucinations), similar to that experienced by patients with narcolepsy.
The NREM/REM sleep states are interrupted by brief arousals and transient awakenings. The frequency of the arousals may increase with emotional disturbance or environmental discomfort but also in many intrinsic sleep disorders such as periodic leg movements in sleep, obstructive sleep apnoea and narcolepsy.
A basic rest/activity cycle originates in fetal life. The newborn sleeps an equal amount during the day and night, the sleep/wake cycle organised around three-to four-hourly feeds. By the second month favouring of sleep towards night-time occurs and by six months the baby will have about 12 hours of sleep at night in addition to a couple of daytime naps.
In general, children born prematurely have a tendency to be awake more at night in the first year and breast-fed babies wake more frequently, but the difference disappears by the second year. Persistent night awakenings in infants and toddlers usually reflect the child's inability to self-soothe back to sleep without parental attention and will respond to a well-supported behavioural programme.
The establishment of a consolidated night sleep pattern in children reflects brain maturation and may be disrupted in children with developmental problems. Even in this group success is possible by persisting with behavioural work, though many paediatricians prescribe melatonin for these children with some success. But as the long-term safety of melatonin remains unknown it should be used as a last resort.
There are now good studies looking at short-term use of melatonin in sleep wake cycle disorders such as delayed sleep phase syndrome. Its use as a hypnotic should be discouraged, especially in the developing child as there is uncertainty on other cycles, such as menstrual.
My view is that GPs should consider helping with ongoing prescriptions only when started by a specialist, after careful discussion with the patient and after other options have been considered.
Larks and owls
In addition to the NREM/REM cycles, there is a circadian (24 hours) sleep/wake cycle entrained by intrinsic rhythms (melatonin and body temperature) and extrinsic factors (light and
social cues such as mealtimes, school/work times).
The pineal hormone melatonin plays a role in entraining the sleep/wake cycle to the light/dark cycle. Melatonin secretion is high in darkness and low in daylight hours, the process beginning in the retina with the supra-chiasmatic nucleus playing a major role as a sleep regulator via melatonin. Blind people may lose this entrainment and develop a free running sleep/wake cycle with progressive advancement of sleep onset time.
Polymorphism of the circadian clock gene has now been identified with the population divided between morning types (larks) and evening types (owls). Those predisposed to later sleep onset time (evening types) are susceptible to developing delayed sleep phase syndrome especially during adolescence when sleep requirement increases and there is a tendency towards later time for sleeping and waking.
In delayed sleep phase syndrome, sleep onset is delayed to the early hours of the morning with consequent difficulty in waking in time for school/ work. Once established, advancing sleep onset time is difficult and requires treatment with appropriately timed melatonin or bright light therapy, or chronotherapy – advancing sleep onset progressively forwards until the desired sleep time is reached.
In contrast the elderly who are more susceptible to perturbation in their sleep/wake schedule can develop advanced sleep phase syndrome with sleep onset occurring early in the evening. Shift workers often struggle to cope with shift patterns as they grow older due to difficulty in re-adjusting their circadian clock. In general, morning bright light exposure is a more powerful synchroniser of the circadian rhythm than melatonin.
Many physiological regulatory mechanisms are altered in sleep. REM sleep is physiologically more unstable when cardio-respiratory and temperature regulation instability and increase in cerebral blood flow may lead to medical emergencies in the vulnerable. REM sleep has been implicated in sudden infant death syndrome.
How much sleep?
Total sleep requirement varies with age from 16 hours in the newborn to seven to seven-and-a-half in the adult with marked individual variability in the elderly. Sleep stage distribution changes with age. Children have more deep sleep and can be very difficult to wake in the first half of the night, increasing their tendency to night terrors and sleep walking behaviours (especially if genetically predisposed) occurring on sudden arousal from deep NREM sleep. In contrast there is a decline in NREM stages 3 and 4 sleep in the elderly.
Restless leg syndrome
It is essential to exclude restless leg syndrome (RLS) in patients complaining of insomnia. Patients with RLS report uncomfortable, unpleasant sensations usually in the legs but sometimes also involving the arms, with an urge to move the limbs, the symptoms relieved by movement. The symptoms usually occur in the evening or at night.
At the severe end of the spectrum RLS will prevent sleep onset, the patients pacing the floor until they fall asleep with exhaustion. At the milder end the RLS symptoms are intermittent, but the sleep is chronically disturbed by the associated periodic leg movements in sleep producing arousals.
It is important to be familiar with the range of colloquial expressions used including 'Elvis legs', crazy legs, maggots crawling and so on, as this disorder which is often familial can be effectively treated.
Some patients respond to iron replacement therapy or codeine preparations with an anticonvulsant. Dopaminergic agonists like pramipexole, ropinirole or cabergoline can be very effective if symptoms are severe and persistent.
Excessive daytime sleepiness
Excessive daytime sleepiness (EDS) can be multi-factorial from insufficient night sleep to sleep wake cycle disorder or organic sleep disorders such as narcolepsy or obstructive sleep apnoea (OSA).
Differentiating fatigue from sleepiness can be difficult. The Epworth sleepiness scale (see further information below) is a standardised subjective scale of propensity to daytime sleepiness and is a useful screen. A score of over 11 usually indicates significant daytime sleepiness needing referral to a sleep centre. EDS can be effectively treated.
Treatment with home continuous positive airway pressure (CPAP) has revolutionised treatment of patients with OSA and recent advances in understanding the pathophysiology of narcolepsy has led to exciting developments for diagnosing this disorder and potential for future cure.
Zenobia Zaiwalla is consultant neurophysiologist, Park Hospital for Children and Radcliffe Infirmary, Oxford
lRestless leg symptoms – if neurological examination normal, check serum ferritin and exclude secondary causes, such as renal disorder. See response to iron if ferritin level below 50 micrograms/litre. Refer to a neurologist or sleep clinic with interest for further assessment and treatment.
lDifficulty falling asleep followed by normal sleep (delayed sleep phase syndrome) – refer to a sleep centre with interest.
lDifficulty initiating/maintaining sleep – no major psychiatric problems/depression, refer to a psychologist or sleep centre with interest.
Excessive daytime sleepiness
lEpworth score >11 and depression/insufficient night sleep excluded – refer to a sleep centre.
Sleep-wake cycle disorder
lPersistent – refer to a sleep centre with interest.
lPersistent behaviours, such as night terrors/sleep walking – refer to psychologist/sleep centre with interest.
REM behaviour disorder a possibility – refer to a neurologist/ sleep centre with interest.
lDiagnosis not clear/epilepsy suspected – refer to a neurologist or sleep centre with interest and expertise.
*For sleep service providers directory, including diagnostic facilities and areas of interests, contact British Sleep Society: www.sleeping.org.uk
www.sleeping.org.uk/news/documents/Guidelines.pdf (Epworth scale in appendix 3)
Solve Your Child's Sleep Problems, R.Ferber (Dorling Kindersley, 1986)
Solving Children's Sleep Problems, L.Quine (Beckett Karlson, 1997)