NEFL and diabetes mellitus: In the DM group, there was a significant correlation between plasma NfL level and age (r = 0.40, 95% CI: 0.28, 0.51, p < 0.0001), but not between serum creatinine level and age (r = 0.07, 95% CI: − 0.07, 0.21, p = 0.30).