Univariate genetic analysis of oxygen transport regulation in children: the Medical College of Virginia Twin Study.

We investigated the relative contributions of genetic, individual environmental, and shared environmental effects on 2,3-diphosphoglycerate (DPG) regulation in preadolescent children. In a population of 165 early pubescent boy and girl twin pairs (11.4 y old), of whom 63 were passive smokers, we asked: 1) Are there differences in the control of DPG levels between early pubertal boys and girls? 2) If present, are these differences influenced by exposure to passive cigarette smoke? Non-passive-smoking boys and girls had similar DPG levels. With exposure to passive smoke, DPG levels increased in boys (p = 0.02) but not in girls. Analysis of variance on DPG demonstrated a parental smoking effect (p = 0.008) and suggested an interactive effect between parental smoking and sex of the child (p = 0.08). Univariate genetic analyses suggested that genes operated at different magnitudes in boys (9%) and girls (39%) in explaining a significant portion of the variance in DPG. The magnitude of shared environmental influences was greater in boys (62%) than in girls (34%), whereas individual environmental effects were similar in boys (29%) and girls (26%). Early pubertal boys differ from girls in their regulation of DPG. Environmental stressors such as passive cigarette smoke may elicit different responses in males and females, even at an early age. The use of path analysis may provide important insights into the mechanisms and interactions of genetic and environmental effects that underly the childhood antecedents of atherosclerotic heart disease.