Background: To identify the effect of certain factors on insomnia in the general population.
Methods: A self-reported questionnaire survey was conducted among 648 Japanese women living in the residential area of a city. Age of participants ranged from 20 to 80 s.
Results: The crude prevalence of insomnia was 8.8%. Multivariate logistic regression analysis with control for many confounding variables revealed that experiencing a major life event (OR=4.4, 95% CI=1.7-11.4, P<0.01), depressive state (OR=1.2, 95% CI=1.1-1.3, P<0.01), and 'relatively poor or poor' self-rated health (OR=3.2, 95% CI=1.0-10.1, P<0.05) were risk factors for insomnia. By contrast, there was no dose-response relationship between the distance of our subjects from a major road and prevalence of insomnia.
Conclusions: The authors assume that depressive state by a major life event is closely associated with insomnia and that relatively poor self-rated health is also associated with stressful event and psychological distress. Although the noise from vehicles such as cars or motorcycles can affect the quality of sleep for subjects who live near a major road, in general the prevalence of insomnia did not increase significantly in this study.