Racial differences in the influence of body size on ambulatory blood pressure in youths

Background African Americans have higher night-time blood pressures than Ca ucasians do despite their having similar daytime blood pressures, It is wel l established that body size is related to casual blood pressure. Objective To examine the influence of body size on racial differences in pa tterns of ambulatory blood pressure. Methods Ambulatory blood pressure recordings were performed on 292 healthy children and adolescents (148 African Americans and 144 Caucasian) aged 10- 18 years (mean 13 +/- 2 years), These blood pressures were related to heigh t, weight, body surface area, and body mass index in separate regression mo dels that also included race, sex, and age as factors. Results The race-by-height interaction was significant for night-time systo lic blood pressure (P < 0,02), with a significant relationship for African Americans (P < 0.0001), but not for Caucasians. The race-by-weight interact ion was significant for night-time systolic blood pressure (P < 0,04), also with a greater relationship for African Americans (P < 0.0001) than for Ca ucasians (P < 0,03), In addition, the race-by-weight interaction was signif icant for night-time diastolic blood pressure (P < 0,04), with a significan t relationship for African Americans (P < 0.01), but not for Caucasians. Fi nally, the race-by-body-surface-area interaction was significant for night- time diastolic blood pressure (P < 0,05), again with a significant relation ship for African Americans (P < 0.02) but not for Caucasians, Conclusion Differences in the relationship between body size and blood pres sure contribute to the racial differences in patterns of ambulatory blood p ressure and should be considered when evaluating patterns of blood pressure in African American youths. (C) 2000 Lippincott Williams & Wilkins.