The upper airway obstruction is either complete, in which case the person completely stops breathing (apnea), or partial, causing a partial cessation of breathing (hypopnea). There are three types of sleep apnea. Obstructive sleep apnea is the most common form of sleep apnea (84% of cases); the other two types are central sleep apnea (0.4%) and mixed sleep apnea, a combination of obstructive and central sleep apnea (15%) (Villines, 2021). Prevalence It is currently estimated that 15 to 30 percent in males and 10 to 15% of females in North America have obstructive sleep apnea when it is defined as an (AHI) of at least 5 events per hours of sleep (Kline, 2021).These characteristics meet the definition of OSA. It is also estimated that among adults aged 30 to 70, approximately 13% of men and 6% of women Etiology Two important determinants of upper airway patency are the anatomy of the oropharynx and the tonicity of the upper airway dilator muscles, including the tensor veli and genioglossus, which tend to increase airway dimensions (Mohamed, et al., 2016). Upper airway collapse most often results from a Risk factors The primary risk factors for OSA have been identified in population-based cross-sectional and longitudinal studies. These include: ● Excess body weight (the dominant contributor). ● Male sex. ● Certain craniofacial abnormalities (e.g., macroglossia, narrow mandibular arch, high palatal arch, large uvula, and enlarged tonsils; Poss, 2016). ● Aging. (Mayo Clinic, 2020) In both males and females, the strongest risk factor for OSA is obesity (Strohl, 2018). Obstructive sleep apnea is more strongly correlated with an increased neck size or waist circumference than with general obesity (Kline, 2021).). Craniofacial and upper airway soft tissue abnormalities increase the likelihood of having or developing OSA (Kline, 2021; Poss, 2016). These abnormalities are described later in the section on screening and diagnosis of OSA.
The severity of sleep apnea is defined by the apnea-hypopnea index (AHI), which represents the number of apneas plus hypopneas per hour of sleep. The American Academy of Sleep Medicine (AASM) has defined mild sleep apnea as an AHI of 5 to 15 events per hour, moderate sleep apnea as an AHI of 15 to 30 events per hour, and severe sleep apnea as an AHI of more than 30 events per hour (Laratta, et al., 2017). Obstructive sleep apnea is defined as an AHI of 5 or greater, with associated symptoms (e.g., excessive daytime sleepiness), or an AHI of 15 or greater, regardless of associated symptoms. currently have moderate to severe sleep apnea (AHI ≥ 15), also meeting the criteria for OSA. These estimated prevalence rates represent substantial increases over the past two decades (relative increases of between 14% and 55%, depending on the subgroup). The prevalence of OSA in the United States appears to be increasing due to rising rates of obesity (Strohl, 2018). combination of anatomic factors that predispose the airway to collapse during inspiration and insufficient neuromuscular compensation during sleep. In some patients, the tongue falls back into the oropharynx, obstructing the airway (Poss, 2016). Nasal congestion, smoking, and menopause (or post menopause) are additional risk factors for OSA. Various medical conditions are also associated with an increased prevalence of OSA; these include pregnancy, congestive heart failure, end- stage renal disease, chronic lung disease, stroke and transient ischemic attacks, acromegaly, hypothyroidism, and polycystic ovary syndrome (Strohl, 2018).. Regarding edentulous patients, there is no consensus on the effects of wearing conventional complete dentures during sleep (Heidsieck, de Rutter, & de Lange, 2016). Edentulism decreases the size and tonicity of the muscles of the pharyngeal walls which has an adverse effect upon airway patency and when this is coupled with the loss of the vertical dimension of occlusion the incidence of apnea episodes nearly doubles (Rouse, 2017). The results of one meta-analysis indicated that OSA patients who slept with their dentures did not diminish their AHI scores and consequently the severity of their OSA (Vila-Nova TEL, et al., 2021). However, other studies have indicated that wear their dentures at night can diminish the severity of their OSA (Vago, et al., 2022).
CONSEQUENCES OF UNTREATED OBSTRUCTIVE SLEEP APNEA
Several medical disorders are affected by OSA, some quite significantly. The following are some of the more serious adverse medical and social sequelae of untreated OSA. Additional
adverse associations exist with OSA but are outside the scope of this course.
Medical sequelae Cardiovascular diseases
or HF was defined by new reports of myocardial infarction, coronary revascularization procedures, congestive heart failure, and cardiovascular deaths. In a study of 393 patients, the 10-year risk for cardiovascular morbidity and mortality increased with the severity of OSA (Archontogeorgis et al., 2018). Type 2 diabetes mellitus Individuals with OSA have an increased risk for the development of Type II diabetes mellitus and optimizing sleep duration and quality may be a means of improving glycemic control (CDC, 2018). Obstructive sleep apnea appears to be an independent risk factor for insulin resistance and the development of Type II diabetes (Nagayoshi M, et al., 2016). Epilepsy There is an association between OSA and epilepsy (Lin, et al., 2017). In a clinical study of 283 adult epilepsy patients,
Longitudinal and cross-sectional studies have shown a strong association between OSA or hypopnea and hypertension (Bonsinore, et. al., 2019; CDC, 2018). Data from the Wisconsin Sleep Cohort study, a longitudinal study of sleep and sleep disorders, following more than 1,000 adults over more than two decades (Lin, et al., 2017; University of Wisconsin, 2017; Moon, et al., 2021) show that OSA during rapid eye movement (REM) sleep is cross-sectionally and longitudinally associated with hypertension. This finding has particular clinical relevance, because treatment of OSA is often limited to the first half of the sleep period; the REM period, occurring later, is thereby left untreated (Moon, et al., 2021). The Wisconsin Sleep Cohort study found that patients with untreated severe sleep disordered breathing (AHI > 30) were 2.6 times more likely to have “incident coronary heart disease [CHD] or heart failure [HF]” compared with people without sleep disordered breathing. Incident CHD
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