We found that the proportion of CD8+ Tn cells in peripheral blood were positively correlated with severity of autonomic dysfunction (SCOPA-AUT) (correlation coefficient 0.398, 95% CI 0.119–0.676, P = 0.006) and psychiatric complications (SCOPA-PC) (correlation coefficient 2.883, 95% CI 0.179–5.587, P = 0.037), and negatively associated with severity of RBD (RBDSQ) (correlation coefficient − 1.193, 95% CI − 1.886 to − 0.501, P = 0.001) (adjusted R-squared 0.118, F = 6.061, P = 0.001). The gene discussed is CD8A; the disease is complication.