Age and disease contribute to excessive daytime sleepiness in PD

The frequency of excessive daytime sleepiness (EDS) in patients with Parkinson's disease (PD) is almost as high in those who have never used dopamine agonists as those who have, suggesting that age- and disease-related factors also play an important role.The findings come from a recent community-based study in 232 patients with PD, designed to examine the relative importance of drugs, disease, and other clinical and demographic features in the development of EDS. The frequency rates of EDS increased over the 8-year study period from 5.6% at baseline, to 22.5% at four years, to 40.8% at eight years; the 8-year prevalence was 54.2%. EDS was found to be related to age, gender, and the use of dopamine agonists. However, in the subgroup of patients who never used dopamine agonists, the prevalence of EDS increased from 4.1% at baseline to 40.8% at eight years, with an 8-year prevalence of 46.5%. In these patients, hypersomnia was associated with the Hoehn and Yahr stage.Although previous studies have not found age to be independently related to EDS in PD patients, the authors say that their longitudinal results indicate that ageing does contribute to EDS, and this is in accord with more general observations that somnolence increases with age. They note, "This observation suggests and confirms the proposal that a combination of age-related and disease-related biological changes in certain areas of the brain induce or predispose to hypersomnia. However, the far higher occurrence of EDS among patients with PD than among healthy elderly of similar age may indicate that aging only modestly contributes to the emergence of EDS in PD." Although dopamine agonists are recognised to cause drowsiness and were significantly associated with EDS in the study, the authors point out that the frequency of EDS was almost as high among patients who have never used these agents. They say, "This strongly suggests that, although dopamine agonists provoke somnolence in some patients, other factors have a more important role in the development of EDS."...