Relationship between cerebrovascular reactivity and cognition among people with risk of cognitive decline

Background It has been shown that cerebrovascular reactivity (CVR) is correlated with cognitive performance and alterations of CVR may be an indicator of vascular disfunction leading to cognitive decline. However, the underlying mechanism of CVR alterations in BOLD signal is not straight‐forward since other physiological parameters, such as oxygen utilization and blood volume, also contribute to its measurements. In this study, we measured cerebral blood flow (CBF) using a dynamic arterial spin labeling (ASL) technique during a hypercapnia challenge and tested if CVR is related to risk factors of cognitive decline and cognitive performance. Method Sixty‐three subjects (age: 70.17±7.09 yrs, M/F: 18/45; BMI: 27.63±5.07; years in education: 15.79±2.38 yrs; 7 diabetes; 17 hypertension; MMSE score: 28.49±1.40) enrolled in the Wake Forest Alzheimer’s Disease Research Center (ADRC) Clinical Core cohort underwent MRI, including ASL during a hypercapnia challenge with a RespirAct computer‐controlled gas blender, targeting 10mmHg higher end‐tidal CO2 level than the baseline while end‐tidal O2 level is maintained. Pseudo‐continuous ASL (PCASL) was collected during a 3‐minute baseline and a 2‐minute hypercapnic period. The whole brain CVR was obtained by calculating a percent change of CBF per the end‐tidal CO2 elevation in mmHg between the baseline and the hypercapnic challenge (Figure 1). A partial volume correction on CVR and baseline CBF was applied and the whole brain gray matter CVRgm and CBFgm were calculated. Linear regression analyses were performed (CVRgm or CBFgm ∼age+sex+BMI+years of education+diabetes+hypertension+MMSE) to examine the relationship between CVRgm or CBFgm and global cognitive performance (MMSE score). Result CVRgm is positively associated with the MMSE scores (β=0.208, p=0.016) independent of other covariates (Figure 2). CBFgm is negatively associated with age (β=‐0.552, p=0.013) and BMI (β=‐0.623, p=0.037) with the adjustment for all other covariates (Figure 3). Conclusion This study demonstrated that CVRgm is related to lower MMSE scores, while resting CBFgm showed significant relationships with age and BMI. Therefore, CVRgm may be a sensitive imaging parameter relating vascular and cognitive function.