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(Stroke. 2003;34:1871.)
© 2003 American Heart Association, Inc.

Original Contributions

Effect of Aging on Dynamic Cerebral Autoregulation During Head-Up Tilt

From the Department of Geriatric Medicine, Bantry General Hospital, Bantry, Ireland (B.J.C.), and Division of Medicine for the Elderly, University of Leicester, Glenfield Hospital (J.F.P.), and Division of Medical Physics, University of Leicester, Leicester Royal Infirmary (R.B.P.), Leicester, UK.

Correspondence to Dr Brian J. Carey, MD, Department of Geriatric Medicine, Bantry General Hospital, Bantry, Co Cork, Ireland. E-mail careyb2{at}shb.ie

Background and Purpose— Physiological aging is associated with many changes in the cardiovascular and cerebrovascular systems, but dynamic cerebral autoregulation (CA) during supine rest shows no age-related changes. Because syncopal syndromes usually occur during orthostatic stress and their prevalence increases with age, it is important to define the effect of aging on dynamic CA during orthostatic stress.

Methods— Twenty-five younger subjects (40 years) and 25 sex-matched older subjects (60 years) underwent 70° head-up tilt for 30 minutes. Bilateral middle cerebral artery blood flow velocities were measured with transcranial Doppler ultrasound, along with noninvasive continuous measurements of arterial blood pressure, heart rate, and transcutaneous and end-tidal carbon dioxide concentrations. By comparing actual changes in cerebral blood flow velocity to changes predicted by a model based on arterial blood pressure changes, we derived dynamic autoregulatory indexes for each subject for periods before, during, and after tilt.

Results— Younger subjects were a mean of 40 years younger than older subjects (28±8 versus 69±10 years). Although cerebral blood flow velocity (P<0.001) and baroreceptor sensitivity (P<0.001) were significantly lower at rest in older subjects, autoregulatory indexes were similar in younger and older subjects at all times before, during, and after tilt (P=0.62).

Conclusions— Although increasing age is associated with lower cardiac baroreceptor sensitivity and cerebral blood flow velocity, dynamic CA during orthostatic stress is unaffected by physiological aging.

Key Words: aging • cerebrovascular circulation • syncope • ultrasonics

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