Influence on aerobic fitness on aortic stiffness in apparently healthy Caucasian and African-American subjects.

Background: Previous research suggests that arterial stiffness may be significantly higher in African-Americans compared to Caucasians. However, the influence of aerobic fitness on the putative difference in arterial stiffness between these groups has not been previously investigated.

Methods: Two hundred forty-eight subjects (215 Caucasian, 33 African-American) participated in this study. Within one week following enrollment, subjects underwent body mass index (BMI, kg/m2) assessment, cardiopulmonary exercise testing and measurement of aortic wave velocity (AWV, m/s) via magnetic resonance imaging. Initially, 33 Caucasian subjects were randomly age (+/-4 years) and sex-matched (10 male/23 female) to the African-American subjects. 25 Caucasian subjects were then randomly matched for age (+/-4 years), sex (7 male/18 female) and maximal oxygen consumption (VO2Max+/-7 mlO2 kg(-1) min(-1)) to the African-American subjects. Matching based upon VO2Max criteria was not possible for 8 African-American subjects.

Results: In the age and sex-matched analysis, Caucasian subjects demonstrated a significantly higher VO2Max (38.3+/-9.6 vs. 27.9+/-8.6 mlO2 kg(-1) min(-1), p<0.001) and lower BMI (24.5+/-3.2 vs. 29.3+/-6.2 kg/m2, p<0.001) and AWV (5.8+/-1.7 vs. 6.7+/-1.5 m/s, p=0.03). However, when subjects were matched for age, sex and VO2Max, the differences in both BMI (26.8+/-5.5 vs. 27.9+/-5.6 kg/m2, p=0.45) and AWV (6.1+/-1.8 vs. 6.5+/-1.6 m/s, p=0.77) were insignificant.

Conclusions: The results of the present study suggest that previously reported differences in arterial stiffness between Caucasians and African-Americans are at least partially a consequence of a lower level of aerobic fitness in the latter group, a phenomenon that has also been previously demonstrated.