Although the sample of patients is small, it is observed that in the present study, laboratory and clinical variables were not associated with worse sleep quality, which may be due to the uniformity and availability of treatment of these patients for anemia, bone mineral disease, adequacy of dialysis with better technology in hemodialysis machines, and drug treatment (such as erythropoietin, phosphorus binders, and calcimmetics) involved. The gene discussed is EPO; the disease is anemia.