A disease modification effect of APOE E4 on the association between urinary albumin excretion and cognition in Korean adults

Markers of kidney function, genetic variation related to cognitive function, and cognitive performance in the UK Biobank

BACKGROUND

Chronic kidney disease has been linked to worse cognition. However, this association may be dependent on the marker of kidney function used, and studies assessing modification by genetics are lacking. This study examined associations between multiple measures of kidney function and assessed effect modification by a polygenic score for general cognitive function.

METHODS

In this cross-sectional study of up to 341,208 European ancestry participants from the UK Biobank study, we examined associations between albuminuria and estimated glomerular filtration rate based on creatinine (eGFRcre) or cystatin C (eGFRcys) with cognitive performance on tests of verbal-numeric reasoning, reaction time and visual memory. Adjustment for confounding factors was performed using multivariate regression and propensity-score matching. Interaction between kidney function markers and a polygenic risk score for general cognitive function was also assessed.

RESULTS

Albuminuria was associated with worse performance on tasks of verbal-numeric reasoning (β(points) = -0.09, p < 0.001), reaction time (β(milliseconds) = 7.06, p < 0.001) and visual memory (β(log errors) = 0.013, p = 0.01). A polygenic score for cognitive function modified the association between albuminuria and verbal-numeric reasoning with significantly lower scores in those with albuminuria and a lower polygenic score (p = 0.009). Compared to participants with eGFRcre ≥ 60 ml/min, those with eGFRcre < 60 ml/min had lower verbal-numeric reasoning scores and slower mean reaction times (verbal numeric reasoning β = -0.11, p < 0.001 and reaction time β = 6.08, p < 0.001 for eGFRcre < 60 vs eGFRcre ≥ 60). Associations were stronger using cystatin C-based eGFR than creatinine-based eGFR (verbal numeric reasoning β = -0.21, p < 0.001 and reaction time β = 11.21, p < 0.001 for eGFRcys < 60 vs eGFRcys ≥ 60).

CONCLUSIONS

Increased urine albumin is associated with worse cognition, but this may depend on genetic risk. Cystatin C-based eGFR may better predict cognitive performance than creatinine-based estimates.

Albuminuria in Association with Cognitive Function and Dementia: A Systematic Review and Meta-Analysis

OBJECTIVES

Cerebral microvascular disease is considered to contribute to cognitive dysfunction. We opted to explore whether albuminuria, a marker of systemic microangiopathy, is associated with cognitive impairment, dementia, and cognitive function.

DESIGN

Systematic review; independent reviewers screened 2359 articles, derived through the search strategy, for identification of observational studies quantifying an association of albuminuria with the outcomes of interest, abstracted data on study characteristics and results and evaluated studies on quality using the Newcastle-Ottawa scale.

SETTING

Community.

PARTICIPANTS

Adults.

MESUREMENTS

Cognitive impairment and dementia, defined by validated neuropsychological tests or clinical guidelines, respectively, and cognitive function, assessed by validated instruments.

RESULTS

Thirty-two eligible studies were identified. Albuminuria was associated with cognitive impairment (Odds Ratio (OR): 1.35, 95% Confidence Interval (CI): 1.19-1.53; 7,852 cases), dementia (OR: 1.35, 95% CI: 1.10-1.65; 5,758 cases), clinical Alzheimer's disease (OR: 1.37, 95% CI: 1.11-1.69; 629 cases) and vascular dementia (OR: 1.96, 95% CI: 1.16-3.31; 186 cases); the effect remained significant among longitudinal, population-based and high quality studies. Time-to-event analysis on prospective studies of non-demented at baseline individuals also showed a significant association with incident dementia (Risk Ratio: 1.52, 95% CI: 1.16-1.99; 971 cases). Worse global cognitive performance (Hedge's g: -0.13, 95% CI: -0.18, -0.09; 68,348 subjects) and accelerated cognitive decline (g: -0.20, 95% CI: -0.34, -0.07; 31,792 subjects) were noted among subjects with albuminuria, who also scored lower in executive function, processing speed, verbal fluency, and verbal memory.

CONCLUSIONS

Albuminuria was independently associated with cognitive impairment, dementia and cognitive decline. The stronger effects for vascular dementia and cognitive performance in domains primarily affected by microvascular disease support that the association could be mediated by shared microvascular pathology in the kidney and the brain.

Role of Vitamin D in Cognitive Function in Chronic Kidney Disease

Both vitamin D deficiency and cognitive impairment are common in patients with chronic kidney disease (CKD). Vitamin D exerts neuroprotective and regulatory roles in the central nervous system. Hypovitaminosis D has been associated with muscle weakness and bone loss, cardiovascular diseases (hypertension, diabetes and hyperlipidemia), inflammation, oxidative stress, immune suppression and neurocognitive impairment. The combination of hypovitaminosis D and CKD can be even more debilitating, as cognitive impairment can develop and progress through vitamin D-associated and CKD-dependent/independent processes, leading to significant morbidity and mortality. Although an increasingly recognized comorbidity in CKD, cognitive impairment remains underdiagnosed and often undermanaged. Given the association of cognitive decline and hypovitaminosis D and their deleterious effects in CKD patients, determination of vitamin D status and when appropriate, supplementation, in conjunction with neuropsychological screening, should be considered integral to the clinical care of the CKD population.