Abstract WP186: Association Between Blood Pressure, Internal Carotid Artery Flow Parameters And Age-related White Matter Disease

Background: White matter lesions (WML) are associated with hypertension. Blood pressure (BP) is transmitted to the brain via the carotid arteries, and autoregulation helps protect the brain. We investigated if BP via carotid waveform parameters were associated with WML. Methods: We obtained BP measurements from a cohort of community dwelling subjects at mean ages 70±1 and 73±1 years; brain MRI and carotid artery ultrasound at mean age 73±1 years. We calculated mean values of BP (systolic, diastolic, mean, variability and pulsatility), measured WML by volume, and Fazekas scale. We calculated internal carotid artery (ICA) mean blood flow velocity, pulsatility index (PI), and resistivity index (RI). We tested associations between BP and ICA flow parameters and WML using multiple linear regression, corrected for intracranial volume (ICV), age, gender, BMI, previous MI, diabetes, hypertension, smoking, hypercholesterolaemia, PVD and stroke. Results: Amongst 694 subjects, diastolic and mean BP decreased and hence BP pulsatility increased significantly between ages 70 and 73 years. Lower diastolic BP and higher BP pulsatility were associated with higher ICA PI (standardized β, age 70= -0.24, age 73= -0.19, both p<0.001; age 70 β=0.18, p<0.001, age 73 β=0.10, p=0.008 respectively). WML volume was weakly associated with BP at age 70 (diastolic β=0.08, systolic β=0.08, mean β=0.09, all p<0.05) but not with BP variability or pulsatility. Similar but weaker associations were seen at age 73. After adjusting for BP, larger WML volume was associated with higher ICA PI (β=0.10, p=0.012), but not any other measures. All associations were the same for WML Fazekas scores. Conclusions: The relatively weak association between BP and WML may be mediated via ICA pulsatility which is largely driven by falling diastolic BP. This questions the nature of the apparent link between BP and WML.