Vitamin K Status and Cognitive Function in Adults with Chronic Kidney Disease: The Chronic Renal Insufficiency Cohort.

Vitamin K is linked to cognitive function, but studies in individuals with chronic kidney disease (CKD), who are at risk for vitamin K insufficiency and cognitive impairment, are lacking. The cross-sectional association of vitamin K status biomarkers with cognitive performance was evaluated in ≥55-y-old adults with CKD ( N  = 714, 49% female, 44% black). A composite score of a cognitive performance test battery, calculated by averaging the z scores of the individual tests, was the primary outcome. Vitamin K status was measured using plasma phylloquinone and dephospho-uncarboxylated matrix Gla protein [(dp)ucMGP]. Participants with low plasma (dp)ucMGP, reflecting higher vitamin K status, had better cognitive performance than those in the two higher (dp)ucMGP categories based on the composite outcome ( P  = 0.03), whereas it did not significantly differ according to plasma phylloquinone categories ( P  = 0.08). Neither biomarker was significantly associated with performance on individual tests (all P  > 0.05). The importance of vitamin K to cognitive performance in adults with CKD remains to be clarified.