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Author: Gardner, William

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1.	Gardner, William Meyer, Marion Ketterlinus, Robert D.
1.	Discrete-Time Event History Analysis Using Segmented Hazards Experimental Aging Research 17,4 (1991): 251-259. Also: http://www.tandfonline.com/doi/abs/10.1080/03610739108253902 Cohort(s): NLSY79 Publisher: Beech Hill Enterprises Keyword(s): Age at First Intercourse; Event History; Research Methodology; Sexual Activity; Sexual Behavior Permission to reprint the abstract has not been received from the publisher. Event history analysis is a means of explaining variation in the timing of events in individual life histories. This article describes methods for overcoming two difficult problems likely to be encountered in applications of event history analysis to studies of aging and human development. First, in many studies the ages of occurrence of critical life events are recorded in discrete units such as years, but the probability distributions of life events are usually specified in continuous-time form. In this paper, the authors show how to estimate models for discrete-time data based on an underlying continuous-time specification. Second, the standard distributions for life events often fail to capture the complex age- dependence seen in actual data. Also shown is how to construct a model using segmented hazards, that is, a composite of different functions for different segments of time. To illustrate these points, the authors examine the age of first intercourse of 11,883 subjects from the NLSY.
	Bibliography Citation Gardner, William, Marion Meyer and Robert D. Ketterlinus. "Discrete-Time Event History Analysis Using Segmented Hazards." Experimental Aging Research 17,4 (1991): 251-259.

2.	Salsberry, Pamela J. Reagan, Patricia Benton Pajer, Kathleen Gardner, William Fang, Muriel Z. Currie, Lisa
2.	Choosing a Measure of Birth Size in Longitudinal Studies: How Do Various Measures Compare? Presented: Dublin, Ireland, Society for Longitudinal and Life Course Studies (SLLS) International Conference, October 2015 Cohort(s): Children of the NLSY79, NLSY79, NLSY79 Young Adult Publisher: Society for Longitudinal and Life Course Studies Keyword(s): Adolescent Health; Age at Menarche/First Menstruation; Birthweight; Body Mass Index (BMI); Health Factors; Health/Health Status/SF-12 Scale; Methods/Methodology Permission to reprint the abstract has not been received from the publisher. As the fetal origins hypothesis has gained support over the past two decades, an increasing number of studies have used birth size as a predictor for later life health. Birth size is thought to matter because it is a marker of adverse intrauterine conditions that results in various structural, physiological and metabolic changes in the fetus. Empirical tests of the fetal origins hypothesis have generally provided support, but not all studies have found a relationship. This may be related to methodological differences across studies, with wide variation in how birth size is measured. For example, birth size has been captured using birth weight as a continuous measure as well as in categories of low and high weight; others capture gestational age or birth length as part of the measure. Little justification is generally provided regarding the choice of measure. But are these measures the same? Clinical research in maternal-fetal medicine indicates that different birth size measures provide different information about fetal development, thus suggesting that these measures may not be interchangeable. The purpose of this study is: i) to investigate how different birth size indexes predict young adult health outcomes, including age at menarche and BMI, outcomes that are related to adult health; and ii) whether different indexes identify the same group of high risk infants. The US based NLSY79 mother, child and young adult files are used in these analyses. Sample inclusion requires birth data and young adult outcomes on the participants. Regression analyses will be completed. Results from these analyses will help inform researchers about how various measures of birth size compare, providing empirical results to inform decisions regarding the choice of birth size measure in future studies.
	Bibliography Citation Salsberry, Pamela J., Patricia Benton Reagan, Kathleen Pajer, William Gardner, Muriel Z. Fang and Lisa Currie. "Choosing a Measure of Birth Size in Longitudinal Studies: How Do Various Measures Compare?" Presented: Dublin, Ireland, Society for Longitudinal and Life Course Studies (SLLS) International Conference, October 2015.

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