BACKGROUND:Tremor is one of the cardinal symptoms in Parkinson's disease, but only few clinical studies have focussed on its therapy as the primary endpoint. One reason is the substantial fluctuation of tremor severity over time, which is difficult to capture and may render momentary clinical assessments unreliable. METHODS:We evaluated the usefulness of a novel wrist-worn actigraph allowing long-term recordings of tremor in a pilot study, in which we assessed the therapeutic effect of cabergoline on tremor in 10 patients with tremor-dominant Parkinson's disease. Clinical data were obtained by using the Unified Parkinson's Disease Rating Scale (UPDRS Part III, item 20) and simultaneously a patient's tremor diary. RESULTS:We found a significant reduction in UPDRS motor and tremor scores, in tremor duration and tremor amplitude by actigraphy and diaries. Furthermore, we found significant correlations between actigraphy measurements and patient ratings of tremor intensity and occurrence in diaries. CONCLUSION:Long-term actigraphy is a reliable method to assess tremor occurrence and severity and may be used to document antitremor effects in clinical studies.