Differential impairment of psychomotor efficiency and processing speed in patients with chronic kidney disease

Cognitive impairment has been documented in patients with chronic kidney disease. In a recent paper, improvements in cognitive function were seen in hemodialysis (HD) patients switched from conventional HD to nocturnal HD, in two of three domains of cognitive function. Based on these findings, we hypothesized that functional decline may occur differentially in some domains more than others. Using a cross-sectional study design, patients optimized on medical treatment at a predialysis clinic were tested using a battery of neuropsychological (NP) tests measuring three domains of cognitive functioning—attention & working memory skills; psychomotor efficiency & processing speed; and learning efficiency. Clinical subjective symptoms for cognitive functioning and depression were measured using the Patient’s Assessment of Own Functioning (PAOF) inventory and the Beck Depression Inventory (BDI). One hundred and three patients aged 64.6 ± 12.4 years were recruited. Of these, 40% were diabetic, with a mean Charlson comorbidity score of 4.4 ± 2.1. Depression (defined as >16 on the BDI score) was seen in 11 patients. After adjustment for comorbid diseases, hemoglobin, the use of neurodepressor medication, and parathyroid hormone (PTH) values, renal function was negatively correlated with psychomotor efficiency & processing speed, but not with attention & working memory or learning efficiency scores. Chronic kidney disease is associated with a decline in psychomotor efficiency & processing speed, but not with attention & working memory or learning efficiency.