Sleep Disorders Flashcards
Brain theory functions affected by sleep
- Neuronal Communication
- Energy Conservation Theory
- Repair and Restoration Theory
- Information-consolidation Theory
The effect of losing one hour of the day statistic..
AN increase of 20% in the number of heart attacks and road traffic accidents due to the hour of sleep lost
Measurement of Sleep
Brain Wave activity = Electroencephalogram (EEG)
Muscles tone = Electromyogram (EMG)
Eye Movement = Electrooculogram (EOG)
The chemical process of sleep…
Adenosine accumulates in brain during the day, eventually enough to stimulate onset of sleep.
Acting on neurons, and inhibiting ACh neurons in Laterodorasla tegmentum and peduculopntine nucleus.
Inhibits Raphe 5-HT neurosn during REM, whihc generally switch REM off when not inhibited & Hypocretin stimulates these to keep REM off
Adenosine inhibits GABAergic neurons of anterior hypothalamus
Inhibit sleep-active VLPO neurons during the day
Inhibiting this inhibition → VLPO neurons can be active, switch towards sleep
Disinhibited VLPO neurons inhibit wake-active neurons of Raphe Nucleus and tubular mammillary (?) and locus coeruleus nucleus
Galanin
Acts in concert with GABA in hypothalamus, VLPO
Inhibits wake-promoting centres during sleep onset
Inhibit non-REM sleep, allow entry to slow-wave sleep
Once non-REM sleep established, REM waves start in the pons
Hypocretin inhibits these during wakefulness
Move to the geniculate nucleus of the thalamus → Occipital cortex switches on to promote REM sleep
Oscillator controlled by VLPO controls switches back and forth between nREM and REM sleep
Sleep deprivation & subsequent effects:
Affects cardiovascular function- increases SBP which is a risk factor of heart disease
Less than 5 hours sleep a night associated with increased BMI
Outside of 7-8 hours sleep → higher risk of metabolic syndrome
Immune sensitivity and response decreases with sleep deprivation
Insomnia
Affects up to 30% of the adult population at any one time
Chronic insomnia affects 8% of men, 12% of women
May be due to the fact women women are more likely to take drugs that impact on sleep- ie benzodiazepines
Usually a symptom and not a disorder in itself
Often a symptom of many underlying medical, psychiatric (particularly depression) and psychological conditions
May be the presenting symptom of primary sleep disorders
15-20% of insomnias are ‘primary’ (ie. have no organic or psychological cause)
Three categories
1. Onset insomnia- drop of temperature associated with sleep delayed, people can’t fall asleep till later at night
- Disruptive insomnia
- Termination insomnia- people wake too early and can’t get back. Might be due to increased temp, also associated with depression
Treatment of Insomnia
Difficult to treat - in treatment of underlying causes
Sleeping pills may be prescribed for transient insomnia but should not be prescribed long term
Pharmacological treatments
Benzodiazepines
Antihistamines (histamine involved in awakening)
Need to cross BBB to work
Not addictive unlike benzodiazepines
Improving sleep hygiene
Circadian rhythm disorders
Altered with advancing age anyway
Earlier onset of sleepiness, earlier waking times
Jet lag
Temporary desynchronisation between our internal circadian rhythms and external time cues
Symptoms
Symptoms: insomnia / hypersomnia, fatigue, malaise, poor performance which last even past adjusting to new time cues
Shift work
Chronic desynchronisation between internal circadian rhythms and external time cues
Symptoms: insomnia / hypersomnia, fatigue, poor performance, medical / psychiatric illness, drug abuse, social impact
Sleep apnea
Cessation of breathing during REM sleep
Repetitive episodes of decreased airflow during sleep. Decreased airflow may be associated with a reduction in blood oxygen saturation, and enhanced autonomic activity.
Apnoeic events may terminate in arousals, causing sleep fragmentation
Linked to obesity (~50% of cases)
Linked to Sudden Infant Death Syndrome (SIDS)
Restless leg syndrome
Characterised by an almost irresistible urge to move, associated with disagreeable leg sensations
Often interferes with sleep
Symptoms worse at rest, partially relieved by activity
Symptoms worse in the evening or at night
Compared with periodic limb movement (similar but different)
Periodic limb movements
Stereotypic movements of legs (or arms) during sleep
Detected on polysomnography in 90% patients with RLS
May be independent of RLS
May disturb sleep
Narcolepsy
Cataplexy- sudden falling asleep
Relation to hypocretin?
Peptide aids control of sleep-wake cycle
Mice with null mutations of Hrct gene → narcolepsy
Produced from prehypocretin
Expressed in only a few thousand neurons in the dorsolateral hypothalamus- picked up by Hcrtr1 and Hcrtr2 receptors
Active during wakefulness
Widespread projections throughout forebrain, hypothalamus, down to lower areas of the brain
Stabilises “flip-flop” state between sleeping and wakened state by acting on both sleep and wakefulness neurons
Patients have fewer hypocretin neurons, no hypocretin in CSF…
Theory of narcolepsy as autoimmune disorder of these neurons
Neurons are victim of targeted immune response in some patients
