Development and validation of the Japanese version of the Athens Insomnia Scale.
The aim of this study was to develop and validate a Japanese version of the Athens Insomnia Scale (AIS-J). The AIS-J was created using a back-translation design. A total of 477 outpatients with chronic insomnia and 163 individuals from the general community were recruited. Participants were asked to complete the AIS-J along with two other insomnia scales - Japanese versions of the Pittsburgh Sleep Quality Index and the Insomnia Severity Index. The AIS-J consisted of a two-factor structure: 'nocturnal sleep problem' (items 1-5) and 'daytime dysfunction' (items 6-8). Internal consistencycoefficients ranged from 0.78 to 0.88. Correlations between the AIS-J and the aforementioned authorized scales were 0.81 and 0.85, respectively. Scores on the AIS-J were significantly higher for the insomnia group than for the control group. The AIS-J cut-off value for identifying pathological insomnia was estimated at 6 points or more, and the AIS-J-nocturnal cut-off value was estimated at 4 points or more. The AIS-J has sufficient validity and diagnostic utility.