Time Trends in the Incidence of Parkinson Disease

Abstract

In 2008, Morozova et al¹ suggested that smokers have a 74% reduction in risk of Parkinson disease (PD) because some constituents of tobacco may reduce the risk of PD. Under the assumption that smoking is causally associated with PD, they postulated that the drastic decline in smoking frequency that took place in US men after the peak in the 1940s and 1950s would predict an increase in the incidence of PD several decades later.^1,2 However, to our knowledge, their predictions have not been tested empirically, and the long-term time trends for PD remain uncertain.^3-9 Therefore, we studied time trends for parkinsonism overall and for PD over 30 years in a well-defined US population.^3,10-12