Impaired Cerebral Autoregulation in Alzheimer's Disease: A Transcranial Doppler Study

Background: Vasculature changes have been observed in Alzheimer's disease (AD). AD-related vascular pathology might impair cerebral autoregulation (CA). Objective: This study was designed to evaluate CA of AD patients by using transcranial doppler (TCD). Methods: A total of 61 participants were included in the study, including 31 AD patients and 30 controls. The trend curves of cerebral blood flow velocities (CBFV), pulsatility index, and resistance index were obtained using TCD during supine-to-standing posture changes. CA was measured by the changes of CBFV curves during supine-to-standing test. Results: There were two spikes named X spike and W spike that appeared in the CBFV curve when the subjects stood abruptly. The slope of the X spike descending branch, the slope of the W spike ascending branch, and the angle between X and W spikes (alpha angle), showed significant differences between the experimental and control groups (2.34 +/- 0.99 versus 3.15 +/- 1.61 cm/s(2), p = 0.021; 2.31 +/- 0.81 versus 3.38 +/- 1.18 cm/s(2), p < 0.001; and 52.71 +/- 20.26 versus 41.4 +/- 12.87 degrees, p = 0.012, respectively). ROC analysis showed that AUC(alpha angle) is 0.664 (p = 0.028) and that AUC(SAB) and AUC(adjustedSAB) are 0.775 and 0.738, respectively (both p < 0.001). Conclusions: Our study demonstrated that supine-to-standing TCD test is a valuable tool for the evaluation of CA in AD patients. Impaired CA in AD patients manifested as decreased efficiency of changes in the CBFV curve. Neurovascular units were involved in the pathogenesis of AD.