The Association Between Cerebral Oxygenation and CKD in Older Adults

Background: CKD is common, and its prevalence is increasing rapidly worldwide. The aim of this study was to investigate the relationship between CKD and dynamic changes in cerebral oxygenation, which may help explain the link between CKD, cerebrovascular disease, and cognitive impairment. Methods: This observational study used data from waves three (2014–2015) and six (2020–2023) of The Irish Longitudinal Study on Ageing (TILDA), a nationally representative, population-based cohort of community-dwelling adults aged ≥50 years in Ireland. A total of 2,322 participants (mean age 64.7 ± 7.6 years; 53% female) were included.7.1% had CKD, defined by estimated glomerular filtration rate (eGFR). Cerebral oxygenation, indicated by the Tissue Saturation Index, was continuously measured using near-infrared spectroscopy during and after an orthostatic manoeuvre. Results: Participants with CKD were older, had lower levels of educational attainment and higher prevalence of cardiovascular and cerebrovascular disease and cognitive impairment. At wave three, cerebral oxygenation was significantly and independently lower at all time points post-standing in those with CKD (30 s:-0.23 95% CI -0.43 to -0.04, 60 s:-0.31 -0.51 to -0.11, 90 s -0.34 -0.54 to -0.14, 120 s: -0.34 -0.54 to -0.14, 150 s: -0.32 -0.52 to -0.12 and 180 s: -0.36 -0.55 to -0.16, p <0.05). The co-existence of orthostatic hypotension amplified this association at later timepoints while systolic hypotension may mitigate it. Lower eGFR was associated with lower cerebral oxygenation, eGFR 45-59 mL/min/1.73 2 showed the most pronounced decline. Conclusions: CKD is significantly and independently associated with reduced cerebral oxygenation during orthostatic challenge. This may represent a key mechanism linking CKD to cognitive impairment. Further longitudinal studies are warranted to explore the clinical utility of cerebral oxygenation as a predictive biomarker for cognitive decline in CKD.