Age-Period-Cohort Analysis of Abdominal Obesity in Iranian Children and Adolescents: The CASPIAN Study

Background: The assessment of the trend of changes in the prevalence of abdominal obesity can provide useful health information. Objectives: This study aimed to conduct an age-period-cohort (APC) analysis to provide the trend of the prevalence of abdominal obesity in the Iranian pediatric population through the three temporal dimensions of age, period, and cohort. Methods: Data were gathered from a total number of 53,962 Iranian children and adolescents aged 5 to 19 years through four surveys of a national surveillance program (the CASPIAN study) conducted in 2003, 2007, 2011, and 2015. Abdominal obesity was defined as a waist-to-height ratio of >= 0.5. The APC analysis was performed using the "apc_ie" command in STATA software. Results: A significant correlation existed between age, period, and cohort effects and the prevalence of abdominal obesity in children and adolescents. With increasing age, regardless of considerable fluctuations, the prevalence of abdominal obesity followed an overall increasing trend in both genders. The age effect coefficient increased from -2.1 in the age group of 5 - 9 years to 1.1 in the age group of 10 - 14 years and then decreased to 1.0 in the age group of 15 - 19 years among boys; figures followed an increasing trend in girls from -2.2 to 0.8 and 1.5, respectively. As for the period effect, in both boys and girls, the prevalence of abdominal obesity followed an increasing trend when coming from the earlier periods to the recent ones (from -4.6 to 4.0 in boys and from -4.1 to 2.4 in girls). Likewise, this prevalence increased from earlier birth cohorts to the recent ones in both genders. Conclusions: The prevalence of abdominal obesity is increasing among Iranian children and adolescents and this rising trend is affected by age, period, and birth cohort effects. The findings of this study emphasize the necessity of implementing comprehensive interventions for tackling the epidemic of childhood obesity.