Response shift in perception of sleepiness in obstructive sleep apnea-hypopnea syndrome before and after treatment with nasal CPAP.

After nasal continuous positive airway pressure (nCPAP) treatment, several symptoms such as hypersomnolence, daytime fatigue, and impaired concentration improve in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). A variability of perception of pretreatment sleepiness (response-shift phenomenon) experienced in OSAHS patients before and after nCPAP treatment may reflect informative shifts in an individual's internal standards, in values and priorities, or in the conceptualization of perceived sleepiness. The objective of this study is to determine whether there is a response shift in perceptions of pretreatment sleepiness before and after nCPAP treatment in patients with OSAHS. We investigated the response shift in Epworth Sleepiness Scale scores before and after nCPAP.