Methods for Analysis of Longitudinal Data: Blood-Lead Concentrations and Cognitive Development

Abstract This article reports results from a longitudinal study investigating the effects of low-to-moderate prenatal and postnatal lead exposure on the cognitive development of children during the first 18 months of life. Study hypotheses are expressed as a sequence of linear models for the outcome variable adjusted score on the Bayley Scales of Mental Development (MDIA), as a function of cord blood-lead concentration, infant blood-lead concentration at semiannual examinations, and other characteristics of study participants. These models are fitted to MDIA measurements on three occasions for as many as 214 infants, first assuming an arbitrary multivariate covariance structure for the repeated measurements and then with covariance structure arising from a random-effects model for errors. Estimates of the effects of lead exposure are not sensitive to the assumed covariance structure. The article describes several approaches to residual analysis and outlier detection in the longitudinal setting. In particu...

[1]  L. Lillard,et al.  Components of variation in panel earnings data: American scientists 1960-70 , 1979 .

[2]  R. Little Models for Nonresponse in Sample Surveys , 1982 .

[3]  D. Freedman,et al.  Bootstrapping a Regression Equation: Some Empirical Results , 1984 .

[4]  J. Ware,et al.  Random-effects models for longitudinal data. , 1982, Biometrics.

[5]  A. C. Aitken IV.—On Least Squares and Linear Combination of Observations , 1936 .

[6]  R. D. Bock,et al.  A multivariate correction for attenuation , 1975 .

[7]  K. Mather,et al.  Components of variation , 1971 .

[8]  T. Louis Estimating a population of parameter values using Bayes and empirical Bayes methods , 1984 .

[9]  N. Laird,et al.  Maximum likelihood computations with repeated measures: application of the EM algorithm , 1987 .

[10]  R. N. Kackar,et al.  Approximations for Standard Errors of Estimators of Fixed and Random Effects in Mixed Linear Models , 1984 .

[11]  D. Rubin INFERENCE AND MISSING DATA , 1975 .

[12]  N M Laird,et al.  Missing data in longitudinal studies. , 1988, Statistics in medicine.

[13]  C. Waternaux,et al.  Early sensory-motor development and prenatal exposure to lead. , 1984, Neurobehavioral toxicology and teratology.

[14]  C. Morris Parametric Empirical Bayes Inference: Theory and Applications , 1983 .

[15]  D. Bellinger,et al.  The Developmental Consequences of Childhood Exposure to Lead , 1984 .

[16]  Donald B. Rubin,et al.  Selection Modeling Versus Mixture Modeling with Nonignorable Nonresponse , 1986 .

[17]  J. Berger,et al.  Empirical Bayes Estimation of Rates in Longitudinal Studies , 1983 .

[18]  Cheng Hsiao,et al.  Analysis of Panel Data , 1987 .

[19]  S. Weisberg,et al.  Residuals and Influence in Regression , 1982 .

[20]  C Waternaux,et al.  Longitudinal analyses of prenatal and postnatal lead exposure and early cognitive development. , 1987, The New England journal of medicine.