HCRT and Parkinson disease: The median CSF orexin level of patients with PD (272.0 [interquartile range (IQR) = 221.7–334.5] pg/mL) was significantly lower than that of controls (352.2 [296.2–399.5] pg/mL) (Z statistic = 2.72, p = 0.007, effect size r = 0.270).