CHI3L1 and Parkinson disease: In the PD group, age correlated positively with α‐syn (P = .028, R = .286), tau (P = .001, R = .394), YKL‐40 (P < .001, R = .576), and NFL (P < .001, R = .517) and negatively with Aβ42 (P = .037, R = −.263).