Age dependence of brain oxygen metabolism in adults assessed by 3D constrained quantitative BOLD MRI

Global and regional variations in cerebral oxygen metabolism are known to be associated with both healthy aging and the early stages of neurodegeneration. To quantify age effects, a recently developed 3D constrained qBOLD protocol was implemented to determine voxelwise OEF, integrated with ASL-derived CBF measurements to compute CMRO₂. Thirty-four healthy adults (23-87 years) were examined to identify global and regional patterns of cerebral oxygen metabolism across younger (<35, n = 15) and older (>50, n = 19) adults. Whole-brain OEF was greater in older than in younger adults (40.2 ± 5.1 % vs 34.5 ± 4.6 %, P = 0.002), whereas CBF was lower (39.5 ± 10.3 vs 48.3 ± 8.3 mL/100g/min, P = 0.011), resulting in comparable CMRO₂ (144.0 ± 31.8 vs 150.7 ± 30.0 µmol/100g/min, P = 0.537). Across participants, OEF increased by 1.5 % and CBF declined by 2.1 % per decade. Regionally, OEF was greater in older adults within medial temporal lobe (MTL) (37.4 ± 5.9 % vs 32.2 ± 5.1 %), hippocampus (37.2 ± 7.0 % vs 29.1 ± 6.1 %), amygdala (38.3 ± 8.6 % vs 27.9 ± 6.1 %), thalamus (40.5 ± 6.4 % vs 32.5 ± 7.1 %), striatum (42.7 ± 5.3 % vs 36.2 ± 5.5 %), frontal (38.7 ± 5.2 % vs 34.7 ± 5.0 %), parietal (43.9 ± 5.1 % vs 38.2 ± 5.5 %), and occipital (40.7 ± 6.3 % vs 35.1 ± 5.3 %) lobes, all P < 0.05. CMRO₂ differed between older vs younger subjects only in the amygdala (126.6 ± 35.9 vs 97.5 ± 31.6 μmol/min/100 g, P = 0.01). Exploring regional heterogeneity, MTL and its substructures exhibited reduced OEF relative to whole-brain averages in both groups. Overall findings indicate that cerebral oxygen metabolism remains largely preserved throughout adulthood. The combined qBOLD-ASL technique offers a robust framework for detecting regional variations in brain oxygen metabolism, characterizing both normative cerebrovascular aging and possibly early stages of neurodegeneration.