The short Thai version of functional outcomes of sleep questionnaire (FOSQ-10T): reliability and validity in patients with sleep-disordered breathing

Purpose: The study is to evaluate reliability and validity of the short Thai version of Functional Outcome of Sleep Questionnaire (FOSQ-10T), in patients with sleep disordered breathing (SDB). Methods: Inclusion criteria were Thai patients with SDB age ≥ 18 years old who had polysomnography results available. Exclusion criteria were patients unable to complete questionnaire for any reason, patients with a history of continuous antidepressant or alcohol use, and underlying disorders including unstable cardiovascular, pulmonary, or neurological conditions. All participants were asked to complete the FOSQ-10 T and Epworth sleepiness scales (ESS). Of these, 38 patients were required to retake FOSQ-10 T at 2–4 weeks later to assess test–retest reliability, and 19 OSA patients treated with CPAP were asked to do so at 4 weeks following therapy to assess questionnaire’s responsiveness to treatment. Results: There were 42 participants (24 men, 18 women), with a mean age of 48.3 years. The internal consistency of the FOSQ-10T was good, as indicated by Cronbach’s alpha coefficient of 0.85. The test–retest reliability was good, as indicated by intraclass correlation coefficient of 0.77. The correlation between the FOSQ-10T and ESS scores (concurrent validity) was moderate (r = − 0.41). The scores of FOSQ-10T significantly increased after receiving adequate CPAP therapy, showing an excellent responsiveness to treatment. However, there was no significant association between FOSQ-10T scores and OSA severity measured by apnea–hypopnea index. Conclusions: The FOSQ-10T has good reliability and validity to use as a tool to assess QOL in Thai patients with SDB. It is convenient and potentially useful in both clinical and research settings.