Study Objectives: The prospective Self-Efficacy Measure for Sleep Apnea study (SEMSAS) is to determine prevalence of health literacy, self-efficacy and precariousness at obstructive sleep apnea syndrome (OSAS) diagnosis.

Methods: Eligible individuals had confirmed OSAS and were referred to a homecare provider for continuous positive airway pressure (CPAP) therapy initiation. Data on patient characteristics and comorbidities were collected, along with baseline evaluations of self-efficacy (15-item Self-Efficacy Measure for Sleep Apnea tool [SEMSA-15]), precariousness (Deprivation in Primary Care Questionnaire [DipCareQ]), and health literacy (Health Literacy Questionnaire).

Results: Enrolment of 302 patients (71% male, median age 55 years, median body mass index 31.6 kg/m2) is complete. Low self-efficacy (SEMSA-15 score ?2.78) was found in 93/302 patients (31%), and 38 (12.6%) reported precariousness (DipCareQ score >1); precariousness did not differ significantly between patients with a SEMSA-15 score ?2.78 versus >2.78. Health literacy was generally good, but was significantly lower in patients with versus without precariousness, and with low versus high self-efficacy.

Conclusions: SEMSAS is the first study using multidimensional baseline assessment of self-efficacy, health literacy and precariousness, plus other patient characteristics. Data collection continue for CPAP adherence to determine future adherence to CPAP, including CPAP adherence trajectories.