Comparing clinical features of young onset, middle onset and late onset Parkinson's disease.

BACKGROUND Parkinson's disease (PD) affects 1-2% of the population over 65 years. There is evidence that the clinical features differ with age at symptom onset, but published information is scarce. METHODS We reviewed the charts of 593 PD patients and divided them into young onset (≤49 years), middle onset (50-69 years) and late onset (≥70 years) groups. Data collected included age at symptom onset, year of onset, family history of Parkinson's disease in first and second degree relatives, predominant first symptom, first anti parkinsonian medication prescribed, frequency of levodopa-induced dyskinesia, therapy related dystonia, therapy related gastrointestinal side effects, hallucination, dementia, depression and apathy. RESULTS The middle onset was the largest group (51%), followed by the late onset (39%) and the young onset (10%) groups. Young onset patients had a more frequent family history of Parkinson's disease and a longer survival. Symptoms other than tremor were more frequent as the initial symptom of the young onset group, and the frequency of tremor as the first symptom increased with advancing age at onset. Depression was more frequent in the young onset group. The frequency of treatment related dyskinesia or dystonia decreased with advancing age at onset. CONCLUSION We have identified specific clinical differences in Parkinson's disease related to the patient's age at onset and added to the existing knowledge of the variability of disease presentation. We suggest an age of onset of 49 years or less for the definition of young onset PD.