Changes of Cerebrovascular CO 2 Reactivity During Normal Aging

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Abstract
Background and Purpose —During the past decade, transcranial Doppler sonography has widely been used to assess blood flow velocities in the basal intracranial arteries and cerebrovascular reactivity (CR) to various stimuli. Although numerous studies have shown a decline of cerebral blood flow velocity with age, the age dependency of CR, including cerebrovascular CO 2 reactivity, however, is controversial. Recently, we have reported a significant sex-related difference in CR, stressing the need to study the relation between normal aging and CR in both sexes separately. Methods —By means of transcranial Doppler sonography, CR was determined in 100 healthy, nonsmoking volunteers (age 20 to 70 years, 10 men and 10 women per decade). Results —In men, no change of CR with increasing age could be observed ( P =0.98). In contrast, CR in women declined significantly, with a step decrease from the 4th to the 5th decades (F=4.413; P P P Conclusions —There are no changes of CR during normal aging in men, whereas CR declines significantly from the 4th to the 5th decades in women. HRT in postmenopausal women appears to enhance CR.