An Instrument to Measure Functional Status Outcomes for Disorders of Excessive Sleepiness

TLDR

The study develops the Functional Outcomes of Sleep Questionnaire (FOSQ), the first self‑report instrument to assess how disorders of excessive sleepiness affect everyday activities. The authors constructed the FOSQ using three samples—153 individuals seeking sleep care and matched controls, 24 OSA patients from one center, and 51 OSA patients from another—to perform psychometric analyses. Factor analysis identified five subscales, and the FOSQ showed excellent internal (α 0.86–0.91) and test‑retest (r 0.81–0.90) reliability, discriminated between normal and sleep‑problem subjects, and proved suitable for research and clinical use.

Abstract

This article reports the development of the functional outcomes of sleep questionnaire (FOSQ). This is the first self-report measure designed to assess the impact of disorders of excessive sleepiness (DOES) on multiple activities of everyday living. Three samples were used in the development and psychometric analyses of the FOSQ: Sample 1 (n = 153) consisted of individuals seeking medical attention for a sleep problem and persons of similar age and gender having no sleep disorder; samples 2 (n = 24) and 3 (n = 51) were composed of patients from two medical centers diagnosed with obstructive sleep apnea (OSA). Factor analysis of the FOSQ yielded five factors: activity level, vigilance, intimacy and sexual relationships, general productivity, and social outcome. Internal reliability was excellent for both the subscales (alpha = 0.86 to alpha = 0.91) and the total scale (alpha = 0.95). Test-retest reliability of the FOSQ yielded coefficients ranging from r = 0.81 to r = 0.90 for the five subscales and r = 0.90 for the total measure. The FOSQ successfully discriminated between normal subjects and those seeking medical attention for a sleep problem (T157 = -5.88, p = 0.0001). This psychometric evaluation of the FOSQ demonstrated parameters acceptable for its application in research and in clinical practice to measure functional status outcomes for persons with DOES. Thus, the FOSQ can be used to determine how disorders of excessive sleepiness affect patients' abilities to conduct normal activities and the extent to which these abilities are improved by effective treatment of DOES.