Epidemiological approaches to the etiology of Parkinson's disease.

In the search for the cause of Parkinson's disease epidemiology serves several purposes. Valuable clues to the etiology may be derived from the epidemiological features of the disease, and the subsequent search for risk factors in analytical studies can be narrowed correspondingly. On the other hand, knowledge of the epidemiology of Parkinson's disease is necessary in creating etiological hypotheses, since only hypotheses consistent with the epidemiological profile deserve careful testing.