Cerebrovascular reactivity over time course in healthy subjects.

INTRODUCTION: Cerebrovascular reactivity (CVR) reflects the compensatory dilatory capacity of cerebral arterioles to a dilatory stimulus and is an important mechanism for maintaining constant cerebral blood flow. Many pathological conditions are associated with an impaired CVR thus contributing to a higher risk of cerebrovascular disease. Since an impaired CVR might contribute to a cerebrovascular disease if it lasts for a longer period of time, it is of importance to know what the time-course of CVR might be under healthy conditions.
METHODS: We investigated CVR in 33 healthy subjects on baseline and on follow-up after 1 to 3 years. CVR was determined by calculating the difference between maximal blood flow velocity after stimulation with acetazolamide and during rest. Blood flow velocities were measured by transcranial Doppler ultrasound.
RESULTS: CVR did not differ significantly in a group of healthy persons when reevaluated after 1 to 3 years. Possible influencing factors like age, gender, interval between testing, and smoking did not show a significant influence. DISCUSSION: This is the first study to investigate within-subject-differences in healthy subjects. CVR seems to remain constant under healthy conditions. Even this short period of life-span is of importance because an altered CVR can improve under treatment within weeks. Nevertheless further studies should follow-up longer periods of time.