Reliability of reported age at onset for Parkinson's disease.

An individual's age at onset of Parkinson disease (PD) can be collected through a variety of sources, including medical records, family report, and clinical observation. The most common source of PD age at onset information in the research setting is family-report, which is then typically used to classify a subject as juvenile, young, or late age at onset. The reliability of the family-reported age at onset of PD has not been rigorously examined. The present study used data from individuals diagnosed with PD to evaluate the reliability of age at onset information by comparing data obtained from three sources: 1) the subject's medical records, 2) a Family History Questionnaire, and 3) a Subject History Questionnaire. Among the 149 subjects with data for all three age at onset sources, the estimated reliability was R = 0.94. Similar reliability was observed when the sample was stratified based on gender, age at examination, disease duration, first symptom of PD, and years of education. The three measures of age at onset of PD show excellent agreement, strengthening confidence in the reliability of the reported age of clinical onset for PD.