Severe vitamin D deficiency and risk of mild cognitive impairment in patients with chronic kidney disease: A cohort study

Although vitamin D deficiency (VDD) has been linked to cognitive decline in the general population, its impact on cognitive function in patients with chronic kidney disease (CKD) remains unclear. This retrospective cohort study analyzed data from the TriNetX Global Health Research Network database (2010-2022). Adults aged >= 50 years with CKD were categorized into VDD (25-hydroxyvitamin D < 20 ng/mL) or control (>= 30 ng/mL) groups based on measurements at the index date. After propensity score matching, participants were followed for 3 years after a 1-year lag period to assess mild cognitive impairment risk. The matched cohort included 17,545 pairs of patients with balanced baseline characteristics. During follow-up, mild cognitive impairment occurred in 0.8% of the VDD group versus 0.7% in the control group, with no statistically significant difference (hazard ratio [HR]: 1.25, 95% confidence interval [CI]: 0.98-1.58, P = .074). However, sensitivity analysis of patients with severe VDD at baseline (<10 ng/mL) revealed a significantly higher risk of mild cognitive impairment (HR: 1.97, 95% CI: 1.19-3.30, P = .007) and mortality (HR: 1.58, 95% CI: 1.39-1.81, P < .001) compared to the control group. Severe VDD defined at baseline was significantly associated with both cognitive decline and mortality, though this may not reflect persistent deficiency during follow-up. These findings suggest a potential association between baseline vitamin D status and cognitive outcomes in patients with CKD, which may vary with the severity of deficiency. Further prospective studies are warranted to validate these observations.