Random-effect results showed that PD patients had lower CSF levels for Aβ42 (SMD = −0.239, 95% confidence interval [CI]: −0.309 to −0169), p-tau (SMD = −0.302, 95% CI: −0.376 to −0.228), t-tau (SMD = −0.274, 95% CI: −0.349 to −0.200), t-α-syn (SMD = −0.419, 95% CI: −0.542 to −0.295), Zn (SMD = −0.398, 95% CI: −0.623 to −0.173), DJ-1 (SMD = −0.791, 95% CI: −1.380 to −0.202), and YKL-40 (SMD = −0.322, 95% CI: −0.561 to −0.082) (Fig. 3). The gene discussed is CHI3L1; the disease is Parkinson disease.