• test–retest;
  • lifestyle factors;
  • Parkinson's disease


Epidemiological studies of environmental risk factors in Parkinson's disease (PD) are dependent on recollection of past exposures based on patients' self-reports. There are limited studies that have assessed the quality of such data. We conducted a prospective study to determine the test–retest repeatability of environmental and lifestyle factors, and medical data in a PD cohort of Asian ethnicity. A total of 150 consecutive PD patients were initially screened, and 100 were recruited and completed an initial interview. Eighty-three patients completed the second interview more than 6 months later. Lifestyle habits (such as smoking and coffee consumption) showed excellent agreement (κ > 0.90). For the amount and duration of coffee, tea, alcohol, and cigarette smoking exposure, the total agreement in the response for these factors in the repeat interview were noted in 71.4%, 73.3%, 100%, and 90%, respectively (ICC > 0.83). Medical conditions for which the patients were on treatment, such as diabetes, hypertension, and stroke, revealed very high repeatability (κ = 0.81–0.90). Environmental exposures like well-water consumption and prior farm-dwelling produced a moderately good repeatability (κ = 0.66–0.77). In conclusion, our study demonstrates that even over long interval period of more than half a year, self-report lifestyle exposure information, personal and environmental exposure data can be collected with moderate-to-high repeatability from PD patients. © 2008 Movement Disorder Society