APOE4 carriers display loss of anticipatory cerebral vascular regulation over AD progression.

Introduction: Maintenance of cerebral blood flow during orthostasis is impaired with aging and associated with cognitive decline, but the effect of Apolipoprotein 4-allele () is unknown.

Methods: Older adults (n=108) ( carriers, n=47; noncarriers, n=61) diagnosed as cognitively-normal (NC), MCI, or AD participated. Middle cerebral artery blood velocity (MCAv), assessed using Transcranial Doppler ultrasound, and beat-to-beat mean arterial blood pressure (MAP) were continuously recorded during a sit-to-stand transition. Anticipatory and orthostatic-induced MCAv and MAP responses were compared between genotypes and across disease progression.

Results: Cognitively-normal carriers showed greater anticipatory MCAv increase, greater MCAv decrease with orthostasis, and shorter latency of peripheral MAP responses to orthostasis compared to noncarriers. MCAv and MAP responses were delayed and attenuated across the disease progression, with no differences between genotypes in MCI and AD.

Discussion: carriers and noncarriers present with distinct phenotypes of cerebral vascular dysfunction during hemodynamic orthostatic challenge. Unique cerebral and peripheral vascular compensation observed in carriers may be lost as AD progresses.