RACE & GENDER DIFFERENCES IN INTRACEREBRAL & CAROTID ARTERIAL VELOCITY--AGING

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The project studies intracerebral blood flow velocity and resistance, and carotid blood flow velocity using doppler ultrasonography in Baltimore Longitudinal Study of Aging participants. The goal is to determine how these factors, which are associated with cerebrovascular diseases, change with aging and are related to cardiovascular disease. Arterial elasticity can be assessed using carotid ultrasonography, but its association with aortic stiffness has not been completely clarified. We examined the relationship by comparing LCS measurements of aortic stiffness in the BLSA using aortic pulse wave velocity (APWV) and the common carotid artery (CCA) pressure-strain elastic modulus (Ep). Both CCA Ep and APWV increased with age and similarly for women and men. The most parsimonious model to explain APWV included CCA Ep and age (r2=.59, p<.001), but not BP. The association between CCA stiffness and APWV suggest that carotid doppler ultrasonography may be useful in assessing arterial stiffness. We have examined the influence of age and current estrogen replacement therapy (ERT) on common carotid arterial (CCA) stiffness in 172 women, including 37 current postmenopausal ERT users. A stiffness index was defined as the logarithm of the ratio of systolic to diastolic blood pressure (BP) divided by the fractional diameter increase during the cardiac cycle. The stiffness index increased linearly with age (r=0.69, p<0.001), and was lower in ERT users than in postmenopausal nonusers (8.0?2.0 vs 9.7?3.1, p<0.01). The effects of age and ERT on the stiffness index persisted after adjustments for BP and other cardiovascular risk factors. The stiffness index was lower in ERT users than in postmenopausal nonusers after considering the effects of age. Age-associated increases in CCA stiffness are reduced by postmenopausal ERT. The determination of arterial stiffness from carotid doppler requires interactive measurements by the sonographer that adds several minutes to the clinical examination. To simplify the process, we have explored using the shape of the doppler waveform as a measure of arterial stiffness with a program that automatically identifies the shape of the curve. An exponential function was applied to the post-peak ICA Doppler waveform contour. The exponential coefficient, termed 'Decay Index' (DI), was calculated for 108 stenosis-free ICAs and was moderately correlated with APWV (r=0.57) and SBP (r=0.45), and with RI (r=0.54), PI (r=0.44) and SDR (r=0.54), whereas APWV and SBP were also correlated with the resistance measures. DI from stenosis-free ICA is associated with central arterial stiffness and modestly with peripheral resistance. We are currently examining the relationship between several carotid arterial measurements and alcohol usage in the BLSA. We find that mild to moderate alcohol usage is associated with greater arterial elasticity and decreased stiffness in the common carotid artery. A less impressive association was observed with arterial wall thickness and diameter. The changes were independent of blood pressure and age. The response of the artery to alcohol usage may represent one mechanism for its protective effect against cardiovascular disease.