Objective: This study examined the relationship of psychological and health-related quality of life variables to insomnia in a population-based sample.
Methods: Data were derived from a longitudinal epidemiological study assessing the natural history of insomnia. The present results are based on the first of four postal evaluations conducted over a 2-year period. Participants (n=953) completed questionnaires assessing sleep, psychological and personality variables, and health-related factors. Participants were categorized into three sleep status subgroups using an algorithm based on Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision and International Classification of Diseases, 10th Edition diagnostic criteria for insomnia: (1) insomnia syndrome (n=147), (2) insomnia symptoms (n=308), and (3) good sleepers (n=493).
Results: Compared to individuals with insomnia symptoms and good sleepers, individuals with insomnia syndrome presented lower quality of life and higher scores on measures of depression, anxiety, neuroticism, extraversion, arousal predisposition, stress perception, and emotion-oriented coping. The same pattern was observed for individuals with insomnia symptoms in comparison with good sleepers. An ordinal logistic regression analysis showed that the presence of a past episode of insomnia, higher depressive symptoms, and lower scores on the 12-item Short Form Health Survey vitality and role physical subscales were the most useful variables to predict subgroups membership.
Conclusion: The findings indicate that insomnia is associated with increased psychological symptomatology and perceived stress, higher predisposition to arousal, and more impairment of health quality. Longitudinal follow-ups are now being conducted to assess the relative contribution of those variables in the development and natural course of insomnia.