Psychometric properties of an insomnia-specific measure of worry: the Anxiety and Preoccupation about Sleep Questionnaire.

The aim of this study was to examine the psychometric properties of the Anxiety and Preoccupation about Sleep Questionnaire (APSQ), with a focus on factorial validity and internal consistency as well as discriminative, convergent, and association with sleep parameters and daytime impairment. Among a randomly selected sample from the general population (N = 5,000), 2,333 participants completed a survey on nighttime symptoms, daytime symptoms, health outcomes, and psychological processes. The study sample consisted of 1800 participants who did not fulfill criteria for another sleep disorder than insomnia. A two-factor solution, accounting for 70.7% of the variance, was extracted from the 10 APSQ items. One six-item factor determined worries about the consequences of poor sleep (α = .91); the second factor, with four items, assessed worries about the uncontrollability of sleep (α = .86). The two factors were significantly intercorrelated (ρ = .65) and significantly associated with the total APSQ (ρs = .97 and .76, respectively). The APSQ and the two subscales showed discriminant validity between three sleep status groups (normal sleep, poor sleep, and insomnia disorder; R(2) = .33-.41). The APSQ and the subscales demonstrated convergent validity with measures on cognitive arousal, sleep-related beliefs, anxiety, and depression. They also were significantly correlated with sleep parameters and daytime impairment. The findings suggest that the APSQ is a psychometrically sound instrument for assessing worry in insomnia.