Publication:
The Authors American Journal of Human Biology Published by Wiley Periodicals, Inc.
Author:
Michael Leung, Diego G. Bassani, Amy Racine-Poon, Anna Goldenberg, Syed Asad Ali, Gagandeep Kang, Prasanna S. Premkumar, Daniel E. Roth
HBGDki Topics:
Stunting
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Objectives

Conditioning child growth measures on baseline accounts for regression to the mean (RTM). Here, we present the “conditional random slope” (CRS) model, based on a linear-mixed effects model that incorporates a baseline-time interaction term that can accommodate multiple data points for a child while also directly accounting for RTM.

Methods

In two birth cohorts, we applied five approaches to estimate child growth velocities from 0 to 12 months to assess the effect of increasing data density (number of measures per child) on the magnitude of RTM of unconditional estimates, and the correlation and concordance between the CRS and four alternative metrics. Further, we demonstrated the differential effect of the choice of velocity metric on the magnitude of the association between infant growth and stunting at 2 years.

Results

RTM was minimally attenuated by increasing data density for unconditional growth modeling approaches. CRS and classical conditional models gave nearly identical estimates with two measures per child. Compared to the CRS estimates, unconditional metrics had moderate correlation (r 5 0.65–0.91), but poor agreement in the classification of infants with relatively slow growth (kappa 5 0.38–0.78). Estimates of the velocity-stunting association were the same for CRS and classical conditional models but differed substantially between conditional versus unconditional metrics.

Conclusion

The CRS can leverage the flexibility of linear mixed models while addressing RTM in longitudinal analyses.

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