GENETIC INFLUENCES ON AMBULATORY BLOOD-PRESSURE PATTERNS - THE MEDICAL-COLLEGE-OF-VIRGINIA TWIN STUDY

The genetic influence of ambulatory blood pressure and heart rate was examined in 38 pairs of monozygotic twins, 17 pairs of same-sex dizygo tic twins, and 11 pairs of opposite-sex dizygotic twins, all aged 15 o r 17 years. The data were analyzed taking into consideration that the response was multivariate (24-h values) instead of the usual univariat e response. The results demonstrated the heritability of ambulatory bl ood pressure and heart rate. This was true regardless of whether the e stimate of heritability involved monozygotic twin pairs compared to sa me-sex dizygotic twin pairs only, or all dizygotic twin pairs. The tim e-related intraclass correlation coefficient within each twin classifi cation indicated that the patterns of response within twin pairs corre lated more for monozygotic twin pairs than within twin pairs for eithe r set of dizygotic twin pairs. In addition, although the opposite-sex dizygotic twin pairs may have different mean levels of response, they exhibit a similarity of patterns of response akin to that seen within same-sex dizygotic twin pairs.