Clinical Characteristic and Respiratory Disturbance Index as Correlates of Sleep Architecture in Obstructive Sleep Apnea Syndromes Diagnosed with Polysomnography

Kim, S J; Park, D H; Kim, Y S; Woo, J I; Ha, K S; Jeong, D U

Abstract

OBJECTIVES
Obstructive sleep apnea syndrome is common and may produce various symptoms and serious complications. A substantial number of research articles on obstructive sleep apnea syndrome have been published in Korea. However, we found such limitations as lack of sufficient sample size and lack of polysomnography-proven cases. Therefore, we aimed at studying clinical features and sleep structure in a sufficient number of Korean patients with obstructive sleep apnea syndrome diagnostically confirmed with polysomnography.
METHODS
We studied 801 subjects referred to Division of Sleep Studies, Seoul National University Hospital, who were diagnosed as having obstructive sleep apnea syndrome with polysomnography. Subjects were excluded if they had central sleep apnea syndrome, periodic limb movement disorder, narcolepsy or REM sleep behavior disorder. Foreign patients were also excluded. First of all, we studied the clinical features of the subjects. Secondly, we compared sleep-related parameters of the study subjects with those of age/sex-matched normal values. Thirdly, correlations of respiratory disturbance index (RDI) with each of the sleep-related parameters were calculated.
RESULTS
Among the 801 subjects, 668 were male subjects (83.4%) and 133 female subjects (16.4%). Their mean age was 46.6 years(+/-13.5). The mean body mass index (BMI) was 25.8(+/-3.8) and subjects with BMI was over 28.0 accounted for 22.8% of the total. Fifty subjects (6.2%) were found to take benzodiazepines, Mean RDI and mean nocturnal oxygen saturation of all subjects was 31.2(+/-24.4) and 94.5% (+/-3.6), respectively. In comparison with normal values, the subjects showed longer sleep latency, lower sleep efficiency, decreased total show wave sleep %(TSWS %), and decreased total REM sleep % (TREM %)(p<0.01 in all). RDI had a negative correlation with each TSWS % and TREM % (p<0.01, p<0.01). However, RDI did not have significant correlation with either sleep latency or sleep efficiency.
CONCLUSION
In this study, 6.2% of patients diagnosed as having obstructive sleep apnea syndrome were found to take benzodiazepines, although they are generally considered to be of litte benefit or even dangerous because of the respiratory suppressing effect. The proportion of obese subjects was only 22.8% and Korean patients with obstructive sleep apnea syndrome seem to be less obese than those described in foreign journals. This study also suggests that the severity of obstructive sleep apnea syndrome may have a more significant effect on sleep architecture defined as TSWS % and TREM % than on sleep efficiency.