BDNF and chronic kidney disease: In contrast to NfL, the impact of renal function and BDNF has mainly been studied in the context of chronic kidney disease [50] with some studies reporting decreased BDNF level in serum in patients with chronic kidney disease compared to healthy controls [51], while other studies reported no change in serum concentrations of BDNF due to impaired renal function as measured by GFR [52].