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. 2023 Jun 30;38(7):1719-1728.
doi: 10.1093/ndt/gfad013.

Iron deficiency and cognitive functioning in kidney transplant recipients: findings of the TransplantLines biobank and cohort study

Joanna Sophia J Vinke  1 , Aaltje L Ziengs  2 , Anne M Buunk  2 , Lisanne van Sonderen  2 , Antonio W Gomes-Neto  1 ; TransplantLines Investigators; Stefan P Berger  1 , Stephan J L Bakker  1 , Michele F Eisenga  1 , Jacoba M Spikman  2 , Martin H De Borst  1
Affiliations

Iron deficiency and cognitive functioning in kidney transplant recipients: findings of the TransplantLines biobank and cohort study

Joanna Sophia J Vinke et al. Nephrol Dial Transplant. .

Abstract

Background: Neurocognitive impairment is common in kidney transplant recipients (KTRs). Adequate brain functioning requires energy and neurotransmitter activity, for which iron is essential. We aimed to investigate iron deficiency (ID) as a potentially modifiable risk factor for cognitive impairment in KTRs.

Methods: We analyzed stable KTRs participating in the TransplantLines Biobank and Cohort study. Participants underwent neuropsychological tests for memory, mental speed, and attention and executive functioning. ID was defined as ferritin <100 µg/mL or 100-299 µg/mL with transferrin saturation (TSAT) ≤20%. Associations between iron status and norm scores of neurocognitive outcomes, corrected for age, sex and education, were assessed using multivariable linear regression analyses adjusted for potential confounders including hemoglobin.

Results: We included 166 KTRs [median (IQR) age 57 (45-65) years, 59% male, estimated glomerular filtration rate 51±18 mL/min/1.73 m2]. Time since transplantation was 5.8 (1.0-12.0) years. Prevalence of ID was 65%. ID was independently associated with lower scores for mental speed (std.β = -0.19, P = .02) and attention and executive functioning (std.β = -0.19, P = .02), and tended to be associated with worse memory (std.β = -0.16, P = .07). Lower plasma ferritin levels were associated with worse memory (std.β = 0.23, P = .007), mental speed (std.β = 0.34, P < .001), and attention and executive functioning (std.β = 0.30, P = .001). Lower TSAT was associated with worse memory (std.β = 0.19, P = .04) and mental speed (std.β = 0.27, P = .003), and tended to be associated with worse attention and executive functioning (std.β = 0.16, P = .08).

Conclusions: Iron-deficient KTRs performed worse on neurocognitive tasks measuring memory, mental speed, and attention and executive functioning. These findings set the stage for prospective studies addressing whether ID correction restores cognitive function after kidney transplantation.

Keywords: cognitive function; iron; kidney transplant recipients.

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Conflict of interest statement

J.S.J.V. received a speaker fee from Vifor Pharma (to employer). M.F.E. has declared receiving consultant fees from Vifor Pharma; serving on the Advisory Board for Cablon Medical; and receiving speakers bureaus from Vifor Pharma, Cablon Medical and Astellas (all to employer). M.H.d.B. has consultancy agreements with Amgen, Astellas, AstraZeneca, Bayer, Kyowa Kirin, Vifor Fresenius Medical Care Renal Pharma and Sanofi Genzyme, and received grant support from Sanofi Genzyme and Vifor Pharma (all to employer).

Figures

Graphical Abstract
Graphical Abstract
Figure 1:
Figure 1:
Flowchart of included participants. None of the included participants had a Cognitive Screening Test score below the cut-off.
Figure 2:
Figure 2:
Cross-sectional associations of iron status parameters with the combined scores on the domains of cognitive functioning in KTRs. Scatter dot plots were used to show the relation between ferritin (A–C) or TSAT (D–F), both divided into quintiles, and memory (A, D), mental speed (B, E), and attention and executive functioning (C, F). Data are presented as mean ± SD. Norm scores are percentile scores adjusted for age, sex and/or educational level. *P < .05 vs quartile 4 (reference)
See this image and copyright information in PMC

References

    1. Wolfe RA, Ashby VB, Milford ELet al. . Comparison of mortality in all patients on dialysis, patients on dialysis awaiting transplantation, and recipients of a first cadaveric transplant. N Engl J Med 1999;341:1725–30. - PubMed
    1. Legendre C, Canaud G, Martinez F.. Factors influencing long-term outcome after kidney transplantation. Transpl Int 2014;27:19–27. - PubMed
    1. Pliskin NH, Yurk HM, Ho LTet al. . Neurocognitive function in chronic hemodialysis patients. Kidney Int 1996;49:1435–40. - PubMed
    1. Kramer L, Madl C, Stockenhuber Fet al. . Beneficial effect of renal transplantation on cognitive brain function. Kidney Int 1996;49:833–8. - PubMed
    1. Griva K, Thompson D, Jayasena Det al. . Cognitive functioning pre- to post-kidney transplantation—a prospective study. Nephrol Dial Transplant 2006;21:3275–82. - PubMed