Changes of cerebrovascular CO2 reactivity during normal aging

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 CO2 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<0.01) and was significantly higher in the 3rd and 4th compared with the 5th, 6th, and 7th decades (P<0.05). Information on hormone replacement therapy (HRT) in women of the 6th and 7th decades was obtained retrospectively. HRT was associated with enhanced CR (HRT, n=7 versus non-HRT, n=13; P<0.001), with values similar to those found in premenopausal women. 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.