Inclusion Criteria for CKD Participants:  In stages 3b-5 of chronic kidney disease (GFR ≤ 60 ± 5 ml/min/1.73m2) at the first baseline visit in BRINK 1.0. Able to complete an approximately 90 minute cognitive and physical testing battery. Able to sign the informed consent, or allow a caregiver, relative, surrogate, or witness to sign the informed consent if participant is unable to do so.  Inclusion Criteria for non-CKD Participants:  GFR ≥ 60 ± 5 ml/min/1.73m2 at the first baseline visit in BRINK 1.0. Able to complete an approximately 90 minute cognitive and physical testing battery. Able to sign the informed consent, or allow a caregiver, relative, surrogate, and/or witness to sign the informed consent if participant is unable to do so.  Exclusion Criteria:  Exclusion Criteria for CKD and non-CKD Participants:  Acute psychiatric illness that would impede cognitive testing Active chemical dependence Legally blind or unable to complete cognitive tests due to visual loss or deafness