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Hemodialysis.com | Dr. Tamura: Albuminuria Kidney Function and Cognitive Impairment

Author Interview: Dr. Kurella Tamura

Publication:

Author Interview: Dr. Kurella Tamura

Albuminuria, Kidney Function, and the Incidence of Cognitive Impairment Among Adults in the United States.

Kurella Tamura M, Muntner P, Wadley V, Cushman M, Zakai NA, Bradbury BD, Kissela B, Unverzagt F, Howard G, Warnock D, McClellan W.
Division of Nephrology, Stanford University School of Medicine, Palo Alto, CA; Geriatric Research and Education Clinical Center, Palo Alto VA Health Care System, Palo Alto, CA.
Am J Kidney Dis. 2011 Aug 2.

What are the main findings of the study?

What are the main findings of the study? We found that albuminuria and low estimated GFR (glomerular filtration rate) were complementary but not additive risk factors for cognitive impairment in a large cohort of US adults.  That is, when estimated GFR was preserved, albuminuria independently predicted cognitive impairment.  When albuminuria was low or absent, low estimated GFR independently predicted cognitive impairment.

Were any of the findings unexpected?

Were any of the findings unexpected? Previous studies have shown that albuminuria and low estimated GFR were independent risk factors for death, cardiovascular events, and ESRD.  We expected but did not find a similar relationship for cognitive impairment, and we speculate that this finding may reflect some distinct aspects about the pathophysiology of cognitive impairment versus other vascular outcomes.

What should clinicians and patients take away from this study?

What should clinicians and patients take away from this study? One important take-home point is that patients who have a preserved estimated GFR (>60) but albuminuria were at the highest risk for cognitive impairment in our study. 

What recommendations do you have for nephrology health care providers as a result of your study?

What recommendations do you have for nephrology health care providers as a result of your study? Markers of kidney function such as GFR and albuminuria may prove to be useful and simple measures to assess future risk for dementia and cognitive decline.

Abstract:

BACKGROUND:

Albuminuria and estimated glomerular filtration rate (eGFR) are each associated with increased risk of cognitive impairment, but their joint association is unknown.

STUDY DESIGN:

Prospective cohort study.

SETTING & PARTICIPANTS:

A US national sample of 19,399 adults without cognitive impairment at baseline participating in the REGARDS (Reasons for Geographic and Racial Disparities in Stroke) Study.

PREDICTORS:

Albuminuria was assessed using urine albumin-creatinine ratio (UACR) and GFR was estimated using the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation.

OUTCOMES:

Incident cognitive impairment was defined as score ≤4 on the 6-Item Screener at the last follow-up visit.

RESULTS:

During a mean follow-up of 3.8 ± 1.5 years, UACRs of 30-299 and ≥300 mg/g were associated independently with 31% and 57% higher risk of cognitive impairment, respectively, relative to individuals with UACR <10 mg/g. This finding was strongest for those with high eGFRs and attenuated at lower levels (P = 0.04 for trend). Relative to eGFR ≥60 mL/min/1.73 m(2), eGFR <60 mL/min/1.73 m(2) was not associated independently with cognitive impairment. However, after stratifying by UACR, eGFR <60 mL/min/1.73 m(2) was associated with a 30% higher risk of cognitive impairment in participants with UACR <10 mg/g, but not higher UACRs (P = 0.04 for trend).

LIMITATIONS:

Single measures of albuminuria and eGFR, screening test of cognition.

CONCLUSIONS:

When eGFR was preserved, albuminuria was associated independently with incident cognitive impairment. When albuminuria was <10 mg/g, low eGFR was associated independently with cognitive impairment. Albuminuria and low eGFR are complementary, but not additive, risk factors for incident cognitive impairment.

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