THE CONJOINT TRAIT OF LOW HIGH-DENSITY-LIPOPROTEIN CHOLESTEROL AND HIGH TRIGLYCERIDES IN ADOLESCENT BLACK-AND-WHITE MALES

To evaluate the interrelationships among body composition, blood press ure, and lipid phenotypes in adolescent black and white boys, we asses sed racial distributions of lipids, blood pressure, and obesity and th eir joint occurrence in black and white boys aged 10 to 15 years. Subj ects were recruited from Cincinnati (OH) schools. Because the differen ces in high-density lipoprotein cholesterol (HDL-C) and triglycerides (TGs) are the most profound coronary heart disease (CHD) risk factor d ifferences between black and white males, we assigned subjects to one of four low-HDL-C and high-TG categories (normal and increased risk) u sing the age/race-specific 25th (HDL-C) and 75th (TG) percentiles. We then assessed racial distributions of lipids, blood pressure, and obes ity by these phenotypes. Age differences between the black and whits p articipants were significant, with the former about 3 months younger ( P =.03), but black boys were more mature and were significantly taller and heavier and had a greater body mass index ([BMI] weight in kilogr ams divided by height in centimeters squared). Differences in the sum of the triceps, subscapular, and suprailiac skinfolds were not signifi cant. Blacks had significantly higher HDL-C, lower TG, and higher dias tolic blood pressure (DBP), but differences in systolic blood pressure (SBP) were not significant. In both racial groups, the body compositi on measures were significantly correlated with HDL-C, TG, and blood pr essure levels; the correlations between HDL-C and both weight and BMI were significantly stronger in white boys. The proportion of boys of e ach race with low HDL-C and high TG was similar by design. In both rac ial groups, subjects with the conjoint trait had a significantly great er BMI, triceps skinfold, and sum of skinfolds than subjects in the ot her phenotypic groups. For white boys, participants with the conjoint trait had the highest SEP and DBP; differences in SEP were significant for comparisons to the normal-and high-TG group alone, and difference s in DBP were significant for the comparison between normal and low HD L-C alone. For black boys, subjects with both normal HDL-C and TG had significantly lower SEP than boys with either the conjoint trait or hi gh TG alone: none of the group differences in DBP were significant. Bl ack had significantly less dense LDL (more LDL-C per apolipoprotein [a po] B). In each racial group, boys with the conjoint trait had the mos t dense LDL, significantly more dense than in any of the other phenoty pes in black boys and significantly more dense than in boys with low H DL-C alone and normal boys in the white group. In both racial groups, the occurrence of no risk factors (>75th percentile TG, BMI, SEP, and DBP or <25th percentile HDL-C) and three or more risk factors was grea ter than expected by chance alone, and the occurrence of exactly one r isk factor and two factors was less. When examined by phenotypic group s within race, boys in each racial group with the normal phenotype had a greater than expected percentage with no risk factors, and white bo ys with the conjoint trait were more likely to have a marked increase in multiple risk factors. Possible mechanisms for this clustering of r isk factors and for the racial differences in the patterns are discuss ed. Copyright (C) 1998 by W.B. Saunders Company.