Parent-offspring and sibling body mass index associations during and after sharing of common household environments: the Princeton School District Family Study.

Using the Princeton School Family Study cohort, our specific aim was to determine whether, and to what degree, parent-offspring and sibling associations for measures of body habitus outlast the period of shared common household environment in a single well characterized community. Familial associations of measures in body habitus were assessed in two and three generation kindreds, in parents and their pediatric offspring (less than 20-yr-old), parents and their adult offspring (less than or equal to 20-yr-old), and in pediatric and adult siblings. The cohort included 177 randomly recalled probands and 202 probands from a hyperlipidemic recall group (top decile plasma cholesterol and/or triglyceride). In randomly recalled whites, significant associations of body mass indices in parents and pediatric offspring and in pediatric siblings, and the absence of significant correlations in parents and adult offspring and in adult siblings, emphasize the potency of common household environmental effects relative to within-family similarities for shared body habitus. In whites from the hyperlipidemic recall group, only the mother-pediatric and adult offspring correlations for body mass indices were significant. We speculate that mothers and their offspring from kindreds selected by hyperlipidemic probands are more likely than fathers and their offspring to share eating habits and relative ponderosity, with these communal behaviors outlasting the period of common household environment. Alternatively, and speculatively, in the hyperlipidemic recall group, determinants for ponderosity may be shared more by mothers and their offspring than by fathers and their offspring. Particularly in the random recall group, within-family associations of body mass indices primarily reflect shared common household environments, and probably secondarily, the outcome of genes held in common.