Back to Annual Meeting Page
133rd Annual Meeting & Exposition
December 10-14, 2005
Patrick Crockett, PhD1, Eric Harvey, PhD1, Xuguang Guo, PhD1, David Francis, PhD2, and Pim Brouwers, PhD3. (1) Constella Health Sciences, 2605 Meridian Parkway, Durham, NC 27713, 919-544-8500, email@example.com, (2) Department of Psychology, University of Houston, 4800 Calhoun Rd, Houston, TX 77204, (3) National Institute of Mental Health, 6001 Executive Boulevard, Rockville, MD 20852
For some health effects, one anticipates that an affected population will begin to diverge from normal responses some time after exposure or infection, and it is of interest to be able to characterize the starting time of divergence. As an example, for children born with HIV, scores on neurocognitive tests may be consistent with normal children until a certain age, and then the HIV children may not develop at the same rate after that point. Such data may be modeled with mixed effects models including splines with unknown knots. Others have shown how to include splines into mixed effects models [Ruppert, Wand, and Carroll, 2003], but the locations of knots (the point of divergence in our example) are specified in advance. We present a method for incorporating a linear spline into a mixed effects model, allowing the knot location to be a random effect. We demonstrate the use of the method for longitudinal data (Bayley II scores [Lindsey & Brouwers, 1999]) on children born with (or without) HIV.
Presenting author's disclosure statement:
I wish to disclose that I have NO financial interests or other relationship with the manufactures of commercial products, suppliers of commercial services or commercial supporters.
The 133rd Annual Meeting & Exposition (December 10-14, 2005) of APHA