ABSTRACT
Epidemiology is “the study of distribution and determinants of health-related states in specified populations”(1). This chapter will focus on the distribution of parkinsonism. Unlike laboratory studies where the experimental conditions can be controlled, epidemiology examines natural events occurring in human populations that are influenced by characteristics of the individuals studied as well as by outside forces including medical, economic, and social factors. For these reasons, care must be taken when conducting and reviewing epidemiological studies. No two epidemiological studies are identical. For many reasons, the methods utilized at one location or at one time may not be possible at another and populations vary by time and place. Two primary factors must be considered in studying the epidemiology of parkinsonism, the case definitions used and the population studied.
