Kiyoka Enomoto, Tomonori Adachi, Keiko Yamada, Daisuke Inoue, Miho Nakanishi, Tomohiko Nishigami, Masahiko Shibata

To confirm the psychometric properties of the Athens Insomnia Scale (AIS) among Japanese chronic pain patients. In total, 144 outpatients were asked to complete questionnaires comprising the AIS and other study measures. According to the original article, the AIS has 2 versions: the AIS-8 (full version) and the AIS-5 (brief version). To validate the AIS-8 and AIS-5 among chronic pain patients, we confirmed: 1) factor structure by confirmatory factor analysis; 2) internal consistency by Cronbach's a; 3) test-retest reliability using with interclass correlation coefficients; 4) known-group validity; 5) concurrent validity; and 6) cut-off values by receiver operating characteristic analysis. In addition, semi-structured interviews were conducted to assess the participants' sleep disturbance. If the participants had any sleep complaints, including difficulty in initiating sleep, difficulty in maintaining sleep, and early morning awakening, they were defined as insomnia symptoms. A 2-factor model of the AIS-8 and 1-factor model of the AIS-5 demonstrated good fit. The AIS had adequate internal consistency and test-retest reliability. Patients with insomnia had a higher AIS score than those without insomnia. The sleep disturbance measured by the AIS was positively associated with pain intensity, disability, depression, anxiety, and pain catastrophizing, and negatively associated with pain-related self-efficacy. The cut-off values for detecting insomnia were estimated at 8 points in the AIS-8 and 4 points in the AIS-5. The AIS-8 and AIS-5 had adequate reliability and validity in chronic pain patients.