The improvement in these domains was independent of the baseline apnea/hypopnea index or other indicators of OSA severity. The degree of impairment in quality of life domains but not the severity of disease determined the degree of improvement with nCPAP. In a study by Engleman et al of 204 nCPAP users, there was a significant improvement in daytime sleepiness and a reduction in road traffic incident rate. The use of nCPAP correlated positively with symptoms prior to treatment and not with OSA severity. The reported average (±SD) use of nCPAP in this study was 5.8 ± 2.0 h/night, which is comparable to our average of 6.0 ± 1.6 h/night. One explanation is that patients with more severe OSA but with less perceived impairment in life domains did not use nCPAP regularly and did not report a significant change in their functions. Another reason for the lack of a relationship between OSA severity and the perceived improvement in quality of life could be that patients with severe OSA having cognitive deficit could underestimate the impairment in their own quality of life domains. The patient’s symptoms and especially the degree of sleepiness have been shown to be good predictors of acceptance or compliance with nCPAP therapy. Some patients with mild OSA but with more severe impairment in quality of life measures demonstrated significant increases in SF-36 scores after nCPAP. This type of response has also been observed by other investigators. However, in the latter study, those with a higher apnea/hypopnea index and increased frequency of microarousal had better compliance and greater improvement in quality of life. Although factors other than sleep apnea, such as obesity and comorbidities, can adversely affect the quality of life, the rapid improvement in functions after nCPAP therapy suggests that sleep apnea is the main cause of functional impairment.
We used a general instrument rather than a disease-specific instrument to examine the effect of nCPAP therapy. there Previous studies have already shown improvement in daytime sleepiness and neuropsychiatric manifestations in OSA patients.’ The sleepiness correlated with vitality and general health perception domains of SF-36 in a group of patients with mild to moderate OSA. The fact that some of the SF-36 domains showed significant improvement in the expected direction indicates that this instrument has reasonable sensitivity to show a change after intervention. These types of instruments have the potential for being used in the initial evaluation of OSA patients and perhaps as a predictor of nCPAP response. A nCPAP study with a longer follow-up period is needed to assess the long-term effect of nCPAP treatment on other domains of the quality of life that may have a physical basis.
In conclusion, this study demonstrated a marked impairment of the quality of life in patients with even mild OSA, and that 8 weeks of nCPAP treatment improves the quality of life domains related to vitality, social functioning, and mental health.