FIG. 1.

Illustration of hypothesis: Reported symptoms of PD patients and controls in the prodromal phase of PD with regard to mean age (years, y) at onset (modified from¹⁰ and²⁸). The schema of stages of PD and image of brain are used with friendly permission of Braak et al.¹⁰ * P-value for the test < 0.05. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]