Morphometric analysis of the uvula in patients with sleep-related breathing disorders

The upper-airway mucosa in obstructive sleep apnea (OSA) patients and snorers is often described as edematous and hyperplastic. The morphologic aspects of the pharyngeal mucosa, and in particular the mucosa of the uvula and soft palate, in OSA patients are, however, not well described. The aim of the present retrospective study therefore was to perform histologic examination of the pharyngeal mucosa obtained from patients with various forms of sleep-related breathing disorders, including primary snoring. A midsagittal section of uvulas obtained by uvulopalatopharyngoplasty (UPPP) was investigated in 34 OSA patients and 9 non-apneic snorers. Control tissues were taken by autopsy in 19 patients not known to have OSA or snoring. A morphometric point counting technique was used to determine the tissue composition. The data showed that OSA patients and non-apneic snorers had a significantly greater percentage of intercellular space than controls (65.7% vs 54.0%; P = 0.006). Control uvulas contained more muscle than OSA and snorers (14.0% vs 7.8%; P = 0.006). Moreover, the covering epithelium was significantly thicker in OSA and snorers than in controls (variance ratio = 7.64; P = 0.008). When taking body mass index (BMI) into account, no correlation was found between fat deposition and BMI. Findings showed that an increased clinical severity of OSA did not affect the tissue composition. Indeed, uvula morphology was similar in OSA patients with respect to non-apneic snorers. Since the increased amount of intercellular space is the expression of edema, we hypothesize that these mucosal changes together with hyperplasia of the covering epithelium are secondary effects to snoring. They presumably play a minor role in the etiopathogenesis of OSA, but may increase the severity of OSA by further narrowing the pharyngeal lumen.