Dental sleep medicine series 3: Daytime sleepiness

Treating sleepiness is a big part of why we treat sleep. Many but not all patients with SDB will experience sleepiness. There is definite links to workplace and motor vehicle accidents which affect population morbidity and mortality. Often the patients who experience sleepiness are the quickest to accept treatment plans as they want to improve. Conversely, a person with chronic tiredness may be convinced that their condition is the norm and may be the ones who resist diagnoses and treatment the most.

From Sleep medicine 6th edition

Sleepiness is a problem reported by 10% to 25% of the population, depending on the definition of sleepiness used and the population sampled. It is most common in young adults and elderly persons. Sleepiness is a physiologic need state like hunger of thirst, with its intensity evident by how rapidly sleep onset occurs, how easily sleep is disrupted, and how long sleep endures. It is normally expressed in a 24 hour cycle related to the light-dark environmental cycle.

Excessive daytime sleepiness (EDS) can occur in healthy people who have had poor opportunities to sleep or it can be a symptom of serious, life threatening medical conditions.

Within a conventional 24-hour sleep and wake schedule, maximum sleepiness ordinarily occurs in the middle of the night when the individual is sleeping, and consequently this sleepiness typically is not experienced or remembered. When forced to be awake in the middle of the night, one experiences loss of energy, fatigue, weariness, difficulty concentrating, and memory lapses.

Risk factors for increased sleepiness
-Less hours of sleep
-Full time/shift/night work
-Unmarried
-Snoring
-Depression
-Young adults or elderly age

The assessment of sleep
-Behavioural signs: yawning, ptosis, reduced behavioural activity, lapses in attention and head nodding. Factors such as motivation, stimulation and competing needs can reduce the behavioural signs of sleepiness and they can often underestimate the underlying sleepiness.
-Stanford sleepiness scale
-Epworth sleepiness scale
-Multiple sleep latency test
-Maintenance of wakefulness test: Subjects lie in bed or sit in a darkened room and try to remain awake.

Determinants of sleep
-Quantity of sleep: The degree of daytime sleepiness is directly related to the amount of nocturnal sleep. Patients with chronic insufficient sleep exhibit excessive sleepiness and unusually high sleep efficiency and report about 2 more hours sleep on weekends. The rate at which sleep loss occurs is critical and slow adaptation to up to 2 hours sleep loss improves the recovery process.
-Quality of sleep: Arousals affect the quality and continuity of a night's sleep contributing to daytime sleepiness. These arousals are characterized by bursts of EEG speeding or alpha activity and, occasionally, transient increases in skeletal muscle tone. The arousal stimulus differs in different disorders but sometimes can be identified (leg movements, apnoeas, pain). These arousals do not usually cause shortened sleep but will cause fragmentation resulting in daytime sleepiness. Fragmentation, as indexed by number of brief EEG arousals, number of shifts from other sleep stages to stage 1 sleep or wake, and the percentage of stage 1 sleep, correlates with EDS in various patient groups.
-Circadian Rhythms: The circadian rhythm in sleepiness is part of a circadian system in which many biologic processes vary rhythmically over 24 hours. Te sleepiness rhythm parallels the circadian
variation in body temperature, with shortened latencies occurring in conjunction with temperature troughs.

-CNS drugs
Sedating drugs
CNS depressant drugs e.g benzodiazepines and alcohol hasten sleep onset and reduce latency to sleep after night wakening. Second generation antiepileptic drugs have some evidence of sedative effects. Histamine-1 antagonists have sedative effects. Antihypertensive particularly B-adrenergic receptor blockers are reported to cause daytime sedation. Dopaminergic agonists used in treating Parkinson's disease are known to disrupt and fragment sleep as well as cause EDS.
Alerting drugs
Stimulant drugs including caffiene, amphetamine, methylphenidate, pemoline, and modafnil reduce daytime sleepiness
The level of sleepiness can affect the efficacy of the CNS affecting drug. Increased daytime sleepiness can cause an enhanced sedative effect of ethanol. Conversely, Caffiene and methylphenidate causes similar effects in alertness regardless of the basal level of sleepiness.
-CNS pathologies: Idiopathic CNS hypersomnelensce, hypocretin/orexin deficiency in narcoleptics, "sleep attacks" in Parkinson's disease

Public health effects of sleepiness
Nearly half the patients with excessive sleepiness report automobile accidents; half report occupational accidents, some life threatening; and many have lost jobs because of their sleepiness. In addition, sleepiness is considerably disruptive of family life. The highest rate of automobile crashes occurs in the early morning hours, which is notable because the fewest automobiles are on the road during these hours. Also during these early morning hours, the greatest degree of sleepiness is experienced. Long haul truck drivers, graveyard shift workers and medica lresidents are particularly sleepy populations. Cognitive function is also impaired by sleepiness. Adults with various disorders of excessive sleepiness have cognitive and memory problems. Sleepiness also depresses arousability to physiologic challenges: 24-hour sleep deprivation decreases upper airway dilator muscle activity and decreases ventilatory responses to hypercapnia and hypoxia.

Depressed physiologic responsivity due to sleepiness is clinically significant for patients with sleep apnoea and other breathing disorders because they are all exacerbated by sleepiness. The emerging data on sleepiness and pain threshold, cited earlier, are also clinically significant in the management of both acute and chronic pain conditions. Finally, life expectancy data directly link excessive sleep (not specifically sleepiness) and mortality. A 1976 study found that men and women who reported sleeping more than 10 hours a day were about 1.8 times more likely to die prematurely than those sleeping between 7 and 8 hours daily. This survey, however, associated hypersomnia and increased mortality and not necessarily EDS, for which the relation is currently unknown.