In patients with Parkinson’s disease in stages 1–3 according to the Hoehn and Yahr scale (system for describing the motor deficit in PD, first stage—unilateral deficit with minimal disability, third stage—bilateral disease, mild to moderate disability with impaired postural reflexes; the last, fifth stage is confinement to bed or wheelchair unless aided), melatonin was shown to increase BMAL1 expression without normalizing sleep [119]. The gene discussed is BMAL1; the disease is Parkinson disease.