What is the pathophysiology of sleep-disordered breathing (SDB)?

Updated: Feb 13, 2020
  • Author: Vittorio Rinaldi, MD; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Answer

Any factors that decrease upper-airway size or patency during sleep can lead to intermittent obstruction during inspiration, despite inspiratory effort. If the obstruction is sufficiently prolonged, blood oxygen levels drop. Then, the patient arouses or awakens. The arousals disrupt normal sleep architecture. These, together with the oxygenation drops, are responsible for the more severe accompaniments of SDB, including hypertension, arrhythmias, and death. [13]

Factors affecting upper-airway size or patency include numerous anatomic variants and abnormalities (eg, nasal obstruction, retrognathia, macroglossia), obesity, alcohol or sedative intake, and body position during sleep.

Obesity contributes to SDB by changing pharyngeal size and shape. Fat storage in the neck may be particularly associated with risk for SDB, though a subset of patients with SDB are of normal body weight. Many of these patients have a family history of snoring or SDB.

Alcohol intake near bedtime can cause or worsen SDB by reducing the activity of the upper-airway dilating muscles. Alcohol increases both the number and duration of apneic or hypopneic events.

Racial studies and chromosomal mapping, familial studies, and twin studies have provided evidence for a possible link between OSAS and genetic factors. Genetic factors associated with craniofacial structure, body fat distribution, and neural control of the upper-airway muscles likely interact to produce the OSAS phenotype. [14, 15, 16]

Although the role of specific genes that influence the development of OSAS has not yet been identified, some research, especially in animal models, suggests that several genetic systems may be important.

Human leukocyte antigen (HLA)-DQB1*0602 allele, a well-known genetic risk factor for narcolepsy, has been described as a potential genetic factor influencing sleep physiology in individuals diagnosed with OSAS. [17]

Polymorphisms in the serotonin (5-HT) receptor gene can alter its transcription, affecting the number of receptors in the serotoninergic system, contributing to OSAS. [18]

A number of inflammatory factors, such as interleukin (IL)-6, IL-8, and tumor necrosis factor alpha (TNF-α), can be found in high concentrations in persons with OSAS and may serve as biologic markers of this disease. The concentration of these cytokines contributes to weight gain in patients with OSAS and can also modify the risk of obesity-related metabolic disorders, especially insulin resistance. [19]


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