Proposition of a Shortened Version of the Self-efficacy Measure for Sleep Apnea (SEMSA-15): Psychometric Validation and Cut-Off Score for CPAP Adherence

The Self-Efficacy Measure for Sleep Apnea (SEMSA) is a 26-item questionnaire that investigates perceived risks, outcome expectancies and self-efficacy, i.e., the confidence to undertake treatment, in the context of continuous positive airway pressure (CPAP) interventions for sleep apnea syndrome. This questionnaire can be considered too lengthy for clinical practice; therefore, a shortened version is needed. 290 adults undergoing CPAP treatment completed the SEMSA-26. An item reduction process took into account both the results of statistical analyses and the expertise of a steering committee. Construct validity, reliability and external validity were tested for a 15-item short version. Additionally, CPAP adherence (usage more than 4 h per night) was collected, and receiver operating characteristics analyses were performed to establish the cut-off point of the SEMSA-15 that would best classify patients depending on their adherence. The structure of the SEMSA-15 was confirmed by principal components factor analysis. Cronbach’s alpha coefficients ranged from 0.66 to 0.86. The SEMSA-15 dimension scores were highly correlated with their respective SEMSA-26 dimension scores. The self-efficacy sub-score of the SEMSA-15 obtained the best classification performance, with a cut-off point of 2.78 to predict CPAP adherence. The SEMSA-15 seems to be appropriate for use in clinical practice to investigate beliefs and perception of self-efficacy in CPAP interventions. It is, therefore, a useful tool to predict long-term adherence to treatment.