To Örebro University

Objectives: The purpose of this study was to examine the factorial solution of the Modified Somatic Perception Questionnaire (MSPQ) among individuals with insomnia symptoms in the general population.

Design: A cross-sectional study with a randomly selected sample from the general population (N = 3,600; 20-60 year old) was used. In total, 251 of the 2,179 respondents fulfilled the criteria for insomnia symptoms and filled out a survey on demographic parameters, the MSPQ, the Hospital Anxiety and Depression Scale, sleep medication use, and health care consumption.

Methods: Exploratory factor analysis and correlations were used.

Results: The results showed that a two-factor solution, accounting for 47.31% of the variance, was extracted from the 13 items of the MSPQ. While one factor consisting of 10 items determined general symptoms of somatic arousal (a = .83), the other factor with 3 items assessed stomach symptoms and nausea (a = .78). The two factors were significantly inter-correlated (r = .54) and significantly associated with the total MSPQ (r = .96, r = .74). The two factors also showed discriminant validity with anxiety and depression and predictive validity with retrospective reports of sleep medication use and health care consumption. A few significant interactions emerged the two MSPQ factors and degree of sleep complaints.

Conclusions: Although it is often assumed that the MSPQ taps a single factor of somatic arousal, this study on individuals with insomnia symptoms suggests that a two-factor solution has the best fit. Further research on the factorial solution of the MSPQ is warranted.