Biostatistics

Early feeding and growth pattern in infants: Using a three-variate longitudinal model derived from Gaussian copula function


Abstract


Background: The Gaussian copula model was used to generate joint distributions for continuous longitudinal variables and compared with Regular Multivariate Regression Model (RMRM) on infant types of feeding and longitudinal measures of height, weight and head circumference.

Methods: The study was performed longitudinally in rural areas of southern part of Iran, on children from birth to 9 months of age. Out of 319 infants with serial anthropometric measurements from birth, and 2, 4, 6, 7 and 9 months old, 120 infants were included. Infants were divided into three groups (breast fed, formula fed and both milk types). A three-variate longitudinal model including Copula function and RMRM were used to estimate the effect of feeding on growth pattern. All the analyses were performed using SAS version 9.4 (Proc NLmix).

Results: Ninety infants (75%) were breastfed, 16 (13.3%) were formula fed and 14 (11.7%) had combined feeding. Copula model showed that, breast fed children had a better weight gain (β=.627 95% CI 0.217-1.038 P = 0.003), height (β=2.603 95% CI 1.023-4.183 P = 0.001) and head circumference (β=0.8 95% CI 0.069- 1.531 P = 0.0) than formula fed children. R2 and RMSE of the two models were compared and R2 for Copula model was more (wt=0.52, ht=0.96, hc=0.84) than that of RMRM (wt=0.1, ht=0.1, hc=0.09).

Conclusion: Based on R2, Copula model was more precise than RMRM. Estimation of the parameters in copula model indicated that, breast milk consumption had a positive effect on the growth of the infants.

 

Key words: Growth; body measures; breast feeding; multivariate longitudinal model; Gaussian Copula model.

 




DOI: https://doi.org/10.2427/12908

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EBPH Epidemiology, Biostatistics and Public Health | ISSN 2282-0930

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.