An experiment was performed in which α-synuclein was detected in 52% of the general population and its level of expression did not change between ages 40 and 91, while all PD patients with α-synuclein positive and expressed higher α-synuclein levels than that in the age-matched non-PD controls, where AD subjects were no difference from controls [39]. The gene discussed is SNCA; the disease is Parkinson disease.