A two-year follow-up study on the symptoms of sleep disturbances/insomnia and their effects on daytime functioning

Objective: This study attempts to identify changes in the symptoms of sleep disturbances/insomnia over a two-year course and their effects on daytime functioning. Methods: We administered two population-based epidemiological surveys in 2005 and 2007 to participants from rural Japan. Results: In the first survey, 30.7% of the subjects reported sleep disturbances/insomnia. Among them, 60.9% reported sleep problems at the two-year follow-up. A comparison of sleep disturbances/insomnia, and subjective daytime functioning measures between the new incident cases and persistent poor sleepers revealed that the total score of persistent poor sleepers was significantly lower than that of new incident cases on the Pittsburgh Sleep Quality Index and physical quality of life (QoL) but not mental QoL. Longitudinal comparisons of the symptoms of sleep disturbances/insomnia in persistent poor sleepers revealed that sleep efficiency was significantly worse at follow-up. Exacerbation of the symptoms of sleep disturbances/insomnia at follow-up was observed in mild but not severe cases. Conclusions: Sleep efficiency progressively worsens over time, and physical QoL can deteriorate as sleep disturbances/insomnia become chronic. Since the symptoms of sleep disturbances/insomnia and their daytime effects are exacerbated even in mild cases, early intervention and treatment are necessary.