Low-grade impairments in cognitive and kidney function in a healthy middle-aged general population: a cross-sectional study

Abstract

Background Although the relationship between manifest chronic kidney disease and reduced cognitive function is well established, limited data exists on GFR and cognitive function in the general population. Both the brain and kidneys have low-impedance vascular beds, rendering them susceptible to damage from pulsatile blood flow. An association between mildly reduced GFR and cognitive function in the healthy general population may reveal early disease mechanisms underlying low-grade impairment of both organs as well as the possibility for intervention. Our aim was to identify an early stage of low-grade impairments in both the brain and the kidneys in the general population. Methods This investigation was a population-based cross-sectional study that included 1627 participants aged 50–62 years who were representative of the general population in the municipality of Tromsø, Norway. The associations between GFR, measured as iohexol clearance, the urinary albumin-creatinine ratio and performance on five tests of cognitive function—the Digit Symbol Substitution Test, the finger tapping test, the Mini-Mental State Examination and the 12-word test parts 1 and 2 – were examined. The data were adjusted for factors known to be associated with both GFR and cognitive function, including cardiovascular risk factors, medications and education level. Results In multivariate adjusted linear regression analyses, we did not observe associations of the measured GFR or albumin-creatinine ratio with performance on any of the five cognitive tests. In an analysis without adjustment for the education level, an association of worse performance on the Digit Symbol Substitution Test with higher measured GFR ( p = 0.03) was observed. An exploratory analysis revealed an inverse relationship between mGFR and a higher education level that remained significant after adjusting for factors known to influence mGFR. Conclusions We did not find evidence of an association between low-grade impairments in either the kidneys or the brain in the middle-aged general population. A possible association between a high GFR and reduced cognitive function should be investigated in future studies. Electronic supplementary material The online version of this article (10.1186/s12882-019-1356-4) contains supplementary material, which is available to authorized users.

Assessment of cognitive functioning after living kidney donation: A cross-sectional pilot study

“…In the Brain in Kidney Disease Study [10] participants with a eGFR between 30 and 59 ml/min/1.73m 2 performed 0.2 to 0.5 standard deviations below norms in all tested domains of attention and memory. However, consistent with the results of the present study, others did not observe associations between performance on cognitive tests and eGFR or measured GFR in general population samples [35][36][37]. In the general population, low GFR may be a sign of systemic atherosclerosis.…”

Effect of a common UMOD variant on kidney function, blood pressure, cognitive and physical function in a community-based cohort of older adults

“…Although a significant decrease in MMSE values across CKD stages has been reported in frail patients [ 13 ], in the Cardiovascular Health Study, in which cognitive function was assessed by the Modified MMSE and DSST, no significant differences were detected between participants with cystatin C-based eGFR ≥ 90 mL/min/1.73 m 2 and those with eGFR of 60 to below 90 mL/min/1.73 m 2 at baseline [ 30 ]. In addition, in a healthy population aged 50–62 years, a measured GFR below 90 ml/min/1.73 m 2 but >60 ml/min/1.73 m 2 did not associate with several tests of cognitive function, including the DSST and MMSE [ 31 ]. Moreover, a previous study involving the current cohort did not find an association between mild-to-moderate CKD (Stage G3a; defined as eGFR < 45–59 mL/min/1.73 m 2 ) and cognitive performance assessed by MMSE, among other tests [ 32 ].…”

Interactive effect of obesity and cognitive function decline on the risk of chronic kidney disease progression in patients with type 2 diabetes mellitus: a 9.1-year cohort study

“…In contrast, another study reported that weight loss among obese individuals without overt renal diseases was associated with an improvement in glomerular hemodynamic abnormalities [50]. In addition, a cross-sectional study by Småbrekke et al did not find evidence of an association between low-grade cognitive impairment on either the kidneys or brain in a middle-aged general population [51]. Therefore, further studies are needed to clarify the role of normal weight or better cognitive function on the change in CKD risk.…”