Epidemiology of alpha-synucleinopathies: from Parkinson disease to dementia with Lewy bodies.

The epidemiology of the diagnosis of Parkinson's disease and dementia with Lewy bodies is still based on clinical criteria and the definition of the different diseases is still a challenge for clinician and researcher. The epidemiologic estimates of prevalence and incidence are highly affected by differences in diagnostic criteria, geographic location, and methodologic limitations. Studies of prevalence and incidence show increases with advancing age and a higher rate of Parkinson's disease and dementia with Lewy bodies in men compared to women.