Ethnic differences in vascular stiffness and relations to hypertensive target organ damage

OBJECTIVE: People of Black African descent have greater risks of hypertensive target organ damage than would be anticipated for given levels of blood pressure. Arterial stiffness may further account for ethnic differences in risk. DESIGN: Cross-sectional study. SETTING: Population based, London, UK. PARTICIPANTS: One hundred and three Europeans and 99 African Caribbeans aged 40-64 years. METHODS: We measured resting and ambulatory blood pressure, and pulse wave velocity (PWV) of elastic and muscular arteries. Echocardiography measured interventricular septal thickness (IVST). MAIN OUTCOME MEASURES: PWV, IVST. RESULTS: Carotid-femoral PWV was 12.7 m/s 95% confidence interval (CI) 12.3, 13.1 in African Caribbeans and 11.2 m/s (10.9, 11.6) in Europeans (P < 0.0001). This difference persisted on adjustment for resting and ambulatory blood pressure, 12.4 versus 11.5 m/s (P = 0.003). The greater IVST in African Caribbeans (9.6 mm) compared to Europeans (9.1 mm, P = 0.0005), could only in part be accounted for by differences in carotid*femoral PWV. Stiffness in the muscular carotid-radial segment did not differ by ethnicity, but was positively associated with systolic pressure in Europeans (beta regression coefficient 0.033, P = 0.04), and negatively associated in African Caribbeans (-0.036, P = 0.04, and P = 0.02 for interaction). CONCLUSIONS: Aortic stiffness is increased in African Caribbeans compared to Europeans, even when higher blood pressures are accounted for. It is most closely related to IVST, but contributes little to explaining ethnic differences. Stiffness of the upper limb muscular arteries did not differ by ethnicity, but remained favourable in the presence of hypertension in African Caribbeans, while being increased in Europeans. We suggest that this is due to ethnic differences in vascular remodelling.