title: Estimating familial aggregation while adjusting for covariates. Application to pulmonary function data from black and white sibships.
abstract: Although crude correlations are useful in family studies, some adjustment for effects of risk factors that vary both within and among families if often needed. A linear model for estimating sibship correlations while simultaneously considering height, age, race, sex, ascertainment, and smoking status was used on pulmonary function data on 1-second forced expiratory volume (FEV1) and the natural logarithm of the ratio of FEV1 to forced vital capacity (lnFEV%) from 402 adults in 152 white sibships and 172 adults in 59 black sibships. Crude correlations of .271 +/- .048 (FEV1) and .342 +/- .047 (lnFEV%) decreased significantly to .206 +/- .048 and .231 +/- .048, respectively, after adjustment. For black and white sibs, adjusted intraclass correlations, although not statistically different, were .153 +/- .089 and .225 +/- .055 (FEV1), respectively, and were .103 +/- .088 and .275 +/- .054 (lnFEV%), respectively, suggesting that pulmonary function may aggregate more strongly among whites. This analysis illustrates how risk factor adjustment can be readily incorporated into familial correlation studies.
authors.affiliation: Department of Epidemiology, Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD 21205.
authors.forename: M F
authors.initials: MF
authors.lastname: Cotch
authors.forename: T H
authors.initials: TH
authors.lastname: Beaty
authors.forename: A
authors.initials: A
authors.lastname: Muñoz
authors.forename: B H
authors.initials: BH
authors.lastname: Cohen
mesh_terms: D000328:Adult; D044383:Black People; D005190:Family; D005260:Female; D005541:Forced Expiratory Volume / Q000235:genetics; D006801:Humans; D008297:Male; D012044:Regression Analysis; D015656:Respiratory Mechanics / Q000235:genetics*; D012307:Risk Factors; D014797:Vital Capacity / Q000235:genetics; D044465:White People