Estimating the month-specific effect of complementary food on weight loss occurrence rate in less than 2 years old children

  Introduction: Weight loss in children is one of the health problems that could occur several times for a child therefore it is categorized as a recurrent event. In this study, we investigated the weight loss risk factors firstly by using proportional rates model and then by applying time-dependent coefficient rates model.   Materials and Methods: In this study, the information of 1673 babies who were born in 2006 or 2007 and were visited for monthly check ups at Tehran east health centers during their first two years of life were included in the analysis. We first fitted the standard proportional rates model to this data with the purpose of determining weigh loss major risk factors. After adjusting these factors, the month-specific effect of complementary foods on weight loss occurrence rate was explored using time-varying coefficient rates model.   Results: Our findings showed that the risk of weight loss gets heightened as with the increase in the intake of complementary foods. This negative effect is likely to be the most between 9 and 11 months of age and then tends to weaken as the baby grows older. The results of Wald-type statistic showed that the impact of complementary food on the occurrence of weight loss is significantly different with respect to the child ‘age (P