Adaptation of functional outcomes of sleep questionnaire (FOSQ) to Turkish population.

Turkish version of functional outcomes of sleep questionnaire (FOSQ.tr) was examined for its psychometric properties in patients with obstructive sleep apnoea hypopnoea syndrome (OSAHS). The FOSQ was translated into Turkish using a forward-backward translation. For the psychometric evaluation, 73 consecutive patients were selected along with 73 control subjects. Internal consistency, test-retest reliability, concurrent and discriminant validity were investigated. Values of Cronbach's alpha for the total FOSQ.tr (alpha= 0.92) and its sub-scales (alpha= 0.76-0.80) suggest that the questionnaire was consistent internally. Test-retest reliability of the FOSQ.tr was significant for the total score (r= 0.7) and the sub-scales apart from social outcome (r= 0.5 to 0.8, all p< 0.01). FOSQ.tr correlated moderately with Epworth sleepiness scale (ESS), with coefficients ranging from r= -0.5 to -0.62, (all p< 0.05) for the sub-scales, and r= -0.64 (p< 0.01) for total score. Discriminant analysis showed that FOSQ.tr could significantly distinguish the patients from normal subjects (p< 0.03). The psychometric properties of the FOSQ.tr suggest that it is a valid and reliable instrument for the assessment of the impact of disorders of excessive sleepiness on daily behaviour.