Growth velocity of children and its affective factors in northwestern Iran: A longitudinal study using marginal models

Background: Child growth is an important health indicator in human’s lifespan. Evaluating growth variations in infants and children is highly important. This study was conducted to evaluate the risk factors of child growth retardation and determine childhood growth velocity in Zanjan province, Iran. Methods: This longitudinal study was conducted on 7892 children aged 0 to 2 years in Zanjan province in 2013. The sampling method was multi-stage cluster sampling. To determine the growth velocity, 2- pointed model was used. We applied the marginal models of generalized equation estimators (GEE). The related curves were obtained using LOWESS method, and data were analyzed using R Version 2.14.1. Results: In this study, 3879 (49%) of the participants were female, and the mean age of mothers was 27.1±5.4 years. Growth velocity had a significant association with gender, mother’s residency, multiple pregnancies, gestational age, and exclusive breastfeeding (p<0.001). A significant association was observed between gender and weight growth velocity (p<0.001). Moreover, exclusive breastfeeding had a significant association with weight growth velocity (p<0.001). Conclusion: Growth velocity in girls was slightly higher than in boys, however, no considerable difference was found between height growth velocity of girls and boys. The findings of this study also indicated that each month increase in exclusive breastfeeding leads to less growth velocity in children. So, exclusive breastfeeding is strongly recommended to prevent childhood obesity.