Two paths to one destination: altered low-frequency oscillations of cerebral perfusion and oxygenation but not oxygen metabolism in mild cognitive impairment

Cerebrovascular dysfunction, a risk factor for dementia, is challenging to detect in mild cognitive impairment (MCI). Herein, we used novel, light-based technology to investigate low-frequency hemodynamic oscillations (LFOs; 0.02-0.16 Hz) in cerebral perfusion, oxygenation, and relative metabolic rate of oxygen (rCMRO₂) in MCI (<i>n</i> = 13; 74 ± 6 yr) and cognitively intact controls (<i>n</i> = 10; 69 ± 6 yr). Relative cerebral microvascular perfusion and tissue oxygenation changes were recorded using a depth-enhanced optical monitoring system. Continuous wavelet transforms were used to compare average LFO power between groups (α = 0.025). Compared with controls, MCI had lower LFO power in microvascular perfusion, greater power in oxygenation (<i>P</i> ≤ 0.02), and no statistical difference in oscillatory power for rCMRO₂. Similar rCMRO₂ but opposing changes in oscillatory power for cerebral perfusion and oxygenation associated with MCI suggest an adaptation to maintain energy production.<b>NEW & NOTEWORTHY</b> We used a novel, depth-enhanced optical monitoring system to investigate low-frequency hemodynamic oscillations (0.02-0.16 Hz) in cerebral microvascular perfusion, oxygenation, and relative metabolic rate of oxygen in patients with MCI and cognitively intact controls. Our findings indicate cerebrovascular dysfunction in MCI, wherein the regulation of oxygenation is altered to maintain metabolism in an environment with attenuated vascular control. These findings highlight the potential of using optical technology to assess cerebrovascular function in MCI.