Excessive daytime sleepiness in Parkinson disease Is it the drugs or the disease?

Objective: To examine associated demographic and clinical correlates and the development of excessive daytime sleepiness (EDS) over 8 years in a community-based cohort of patients with Parkinson disease (PD). Methods: A total of 232 patients with PD were included in a population-based prevalence study in 1993. Patients were followed prospectively and reexamined after 4 and 8 years. At all study visits, the authors administered semistructured interviews to obtain information on clinical and demographic variables. Standardized rating scales of parkinsonism, depression, and cognitive impairment were used. The diagnosis of EDS was based on a sleep questionnaire and in 2001 also on the Epworth Sleepiness Scale. Population-averaged logistic regression models for correlated data were performed to study the relationship between EDS and various demographic and clinical variables. Results: Of the 232 patients included at baseline, 138 were available for re-evaluation after 4 years and 89 patients after 8 years. Frequency rates of EDS increased from 5.6% in 1993 to 22.5% in 1997 and 40.8% in 2001, with an 8-year prevalence of 54.2%. In the majority of patients, EDS was a persistent feature. In the logistic regression model, EDS was related to age, gender, and use of dopamine agonists. In those never having used dopamine agonists, hypersomnia was associated with the Hoehn and Yahr stage only. Conclusion: Excessive daytime sleepiness is a frequent and highly persistent feature in Parkinson disease, with multifactorial underlying pathophysiology. The authors' findings indicate that both age and disease related disturbances of the sleep-wake regulation contribute to hypersomnia in PD. Treatment with dopamine agonists also contributed to excessive daytime sleepiness in our patients.