Race differences in reproducibilities: The HERITAGE family study

The HERITAGE (HEalth, RIsk factors, exercise Training And GEnetics) Family Study is a multicenter clinical trial conducted by five institutions in the United States and Canada. The overall objective of the study is to investigate the role of the genotype in cardiovascular, metabolic, and hormonal responses to aerobic exercise training and the contribution of regular exercise to changes in cardiovascular disease and diabetes risk factors in white and black families. Since the accuracy of the assessment of the response to training depends on how repeatable or reproducible the measurements are, it is important to assess potential racial differences in reproducibilities, which may have implications for pooling data across races. The sample studied consisted of 96 blacks and 304 whites. The black sample had 46 males with mean age 33.6 ± 14.2 years and 40 females with mean age 33.9 ± 12.7 years. The white sample had 152 males with mean age 35.5 ± 14.9 years, and 152 females with mean age 34.9 ± 14.3 years. Reproducibilities, as measured by intraclass correlations among repeated measures, were comparable between whites and blacks for variables in the anthropometry, i.e, lipid, exercise test, and blood pressure domains. Reproducibilities in both races exceeded 0.85 for most of the variables. When the within-race reproducibilities are very high, statistical significance of any observed racial difference in the reproducibilities may not be very meaningful. There was a significant racial difference in the reproducibility for Apoprotein A1 (0.73 in blacks, 0.89 in whites, P < 0.01). However, this is not a cause for concern, since only one among 37 comparisons was significant. Am. J. Hum. Biol. 9:415–424, 1997. © 1997 Wiley-Liss, Inc.