THE SLEEP-WAKE ACTIVITY INVENTORY - A SELF-REPORT MEASURE OF DAYTIME SLEEPINESS

The purpose of this study was to develop a valid multidimensional self -report measure of sleepiness. There were 554 subjects who completed t he inventory. The structure of the Sleep-Wake Activity Inventory (SWAI ) was derived from principal components analysis. The independent pred ictive strength of the factors was assessed by forward stepwise regres sion analysis with the average sleep latency on the Multiple Sleep Lat ency Test (MSLT) as the dependent variable. The scores on each of the factors were also compared by the level of sleepiness determined by th e MSLT (pathological, diagnostic gray area, and normal). Factor analys is showed the existence of six factors on the SWAI (Excessive Daytime Sleepiness [EDS], Psychic Distress, Social Desirability, Energy Level, Ability to Relax and Nocturnal Sleep). The EDS factor was the best pr edictor of average MSLT. It was also able to differentiate pathologica l levels of sleepiness from both the diagnostic gray and normal levels of sleepiness. EDS factor scores were sensitive to changes in sleep p hysiology as improved scores followed normalization of sleep-disordere d breathing. The SWAI was shown to be easy to complete, have a multi-d imensional structure, have a EDS factor useful in the prediction of av erage MSLT scores, be sensitive to differential levels of sleepiness, and change as a result of effective treatment.