The Association between Cerebral Oxygenation and CKD in Older Adults

KEY POINTS: Older adults with CKD had significantly and independently lower dynamic cerebral oxygenation at all time points on standing. When analyzed by eGFR level, lower eGFR levels were consistently associated with reduced dynamic cerebral oxygenation. Lower cerebral oxygenation in CKD may drive cognitive decline and serve as a marker for risk stratification. 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 Aging, a nationally representative, population-based cohort of community-dwelling adults aged 50 years or older in Ireland. A total of 2322 participants (mean age 64.7±7.6 years; 53% female) were included. 7.1% had CKD, defined by eGFR. Cerebral oxygenation, indicated by the tissue saturation index, was continuously measured using near-infrared spectroscopy during and after an orthostatic maneuver. 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% confidence interval, -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 coexistence of orthostatic hypotension amplified this association at later time points, while systolic hypotension may mitigate it. Lower eGFR was associated with lower cerebral oxygenation; eGFR 45-59 ml/min per 1.73 m 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.