Sleep disorders etiology

The etiology of enuresis is poorly understood, but there is a clear genetic link. The incidence in children from families in whom there are no members with enuresis, where one parent had enuresis as a child, and where both parents had enuresis as children are 14%, 44%, and 77%, respectively. Loci for enuresis have been located on chromosomes 12,13, and 22. Sleep disorders are not considered major contributors with the exception of sleep apnea. Enuresis occurs in all sleep stages in proportion to the time spent in each stage. However, a small proportion of individuals are not aroused from sleep by bladder distention and have uninhibited bladder contractions preceding enuresis. 

Although the etiology of autism is not understood, the defining or core symptoms of autistic disorder are considered to be impaired social interaction, impaired verbal and nonverbal communication, and restrictive, repetitive patterns of behavior. In addition, most patients with a primary diagnosis of autism exhibit other neurological or psychiatric symptoms, which may include seizures, sleep disorders, anxiety, panic attacks, attention deficit/hyperactivity, self-injury, and cognitive impairment (Simonoff et ah, 2008). It is not known to what extent these comorbidities reflect the primary pathology of autism and to what extent they represent unrelated vulnerabilities that are exacerbated by the impaired social interaction and communication that is characteristic of the disorder. 

Causes of excessive daytime sleepiness are numerous and include Intrinsic sleep disorders, such as obstructive sleep apnea/hypopnea syndrome and narcolepsy circadian rhythm sleep disorders, such as jet lag and sleep disorders associated with neuropsychiatric conditions, such as anxiety and depression (42). In many Instances, excessive daytime sleepiness is treated by addressing the underlying cause however, the specific etiology of narcolepsy Is unknown. Narcolepsy also can be characterized by brief periods of muscle paralysis (cataplexy). 

OHS, previously called the Pickwickian syndrome (6), is defined as the association of obesity, sleep-disordered breathing (SDB) with daytime h)q)ersomnolence, and hypercapnia (Pacc>2 > 45 mmHg) in the absence of any other respiratory disease (Fig. 1). SDB can present as obstructive apneas and hypopneas, obstructive hypoventilation due to increased upper airway resistance, and/or central hypoventilation (7). The prevalence of OHS is 36% in patients with BMI between 35 and 40 kg/m, and 48%, if BMI equals or exceeds 50 (8). Without adequate treatment, patients with OHS develop cor pulmonale and recurrent episodes of hypercapnic respiratory failure, and loss of survival (Fig. 2). OHS is one of the many etiologies of CRF and has become a growing indication to initiate longterm noninvasive ventilation (NIV) in most European countries (9,10). 

PI is a disorder characterized by difficulty initiating and/or maintaining sleep. It is distinguished by its etiological independence from other physical or mental disorders. 

Bipolar disorder is characterized by episodes of mania or hypomania, which include hyperactivity, decreased need for sleep, and a euphoric or irritable mood. Additionally, persons with bipolar disorder may have episodes of depression similar to those seen in major depressive disorder. The lifetime prevalence of severe bipolar disorder is about 1% and 3-5% if milder cases are included, afflicting men and women equally. Both bipolar disorder and major depressive disorder tend to be episodic, and in the periods of time between episodes, persons may experience few or no symptoms. The etiology of bipolar disorder is predominately genetic, with a 70% concordance in monozygotic twins. The neurobiology of bipolar disorder is less well understood, and few animal models have been developed. Treatment of bipolar disorder usually involves mood stabilizer medications, including lithium, and the anticonvulsants valproate and carbamazepine. At times, antidepressant and antipsychotic medications are also used. 

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