Insomnia in Parkinson's disease: frequency and progression over time

Objectives: To examine the development of nocturnal sleeping problems in patients with Parkinson’s disease (PD) over an 8-year period and to study the clinical and demographic correlates of insomnia. Methods: 231 patients were included in a population-based prevalence study in 1993, and re-examined in 1997 and 2001. At all study visits, we applied semi-structured interviews to obtain information on clinical and demographic data, as well as on nocturnal sleeping problems. Standardised rating scales of parkinsonism, depression and cognitive impairment were used. The relationship between insomnia and demographic and clinical variables was analysed using population-averaged logistic regression models for correlated data. 231 patients were included at baseline, 142 were available for re-evaluation in 1997 and 89 patients in 2001. Results: Most nocturnal sleeping problems varied little in prevalence over time, whereas problems related to turning in bed and vivid dreaming or nightmares increased. Insomnia was present in 54–60% of the patients at each of the three study visits and varied considerably in individual patients over time. The presence of insomnia was closely related to disease duration, higher Montgomery–Asberg Depression Rating Scale scores and female sex. Conclusion: Insomnia is a highly frequent complaint in patients with PD. It fluctuates over time in individual patients, and its origin seems to be multifactorial. Physicians should be aware of the high prevalence of insomnia in patients with PD and should examine their patients for a possible coexisting depression.