Nationwide Trends of Pediatric Obesity and BMI z-Score From 2017-2021 in China: Comparable Findings From Real-World Mobile- and Hospital-Based Data

Abstract

Introduction: Lifestyle changes including COVID-19 lockdown cause weight gain and may change obesity trends; however, timely changes are largely unknown and monitoring measures are usually lack. This first large-scale study aimed to analyze the real-world national trends of obesity prevalence of Chinese children in the past five years, and the impact of COVID-19 pandemic on pediatric obesity development through both mobile- and hospital-based data.

Methods: This study included children aged 3 to 19 years old all over China from January 2017 to April 2021. Hospital-measured and parent-reported cases from XIGAO database were analyzed. Body mass index (BMI) z-score calculation and obesity status evaluation were made according to Chinese standards. We evaluated obesity/overweight prevalence over the past five years and the changes of BMI z-score during COVID-19 lockdown.

Results: A total of 656396 children from 31 provinces were involved, including 447481 hospital-measured cases and 208915 parent-reported cases. The obesity and overweight prevalence were 8.05% (95%CI 7.76%-8.39%) and 10.06% (95%CI 10.79%-11.55%), comparable to those of China National Nutrition Surveys during 2015-2019. Northern China had the highest obesity prevalence. Parent-reported data had higher obesity/overweight prevalence than hospital-measured data (18.3% [95%CI 17.7%-18.9%] vs. 21.7% [95%CI 20.7%-23.0%]). The trend of obesity prevalence remained stable with slight decrease, but COVID-19 lockdown caused a significant increase of 1.86% in 2020. Both mobile- and hospital-based data showed weight gain in the first half of 2020. High BMI z-score increase were found among primary and junior middle school children, and children in northeast area during lockdown.

Conclusion: Weight gain during COVID-19 among Chinese children had regional differences and mainly affect primary and junior middle school children, thus warrants targeted interventions. The mobile growth assessment based on parent-reported data was a feasible, efficient and timely way for obesity monitoring among Chinese children, especially during epidemic.

Keywords: China; adolescent; body mass index; children; pediatric obesity.

Figure 1

Flow chart of sampling procedure. ^aTo remove the cases that might had growth disorder, we only included the cases whose height age- and sex- specific SDS was between ±2. Then cases with BMI z-score higher than 5 or lower than -5 were excluded in order to excluded incorrect entries and weight abnormalities that might be secondary to other diseases. ^bEach child had a unique ID. Cases that repeatedly registered data in both the hospital database and the mobile database were regarded as repeated cases, and data from mobiles were excluded.

Figure 2

Characteristics of the standardized prevalence of obesity and overweight and BMI z-score. (A) The standardized prevalence of obesity by province. (B) The standardized prevalence of obesity and overweight by province. The prevalence was standardized by sex and age in different provinces. This study didn’t included children in Taiwan, Hong Kong and Macao. Cases in Tibet Autonomous Region and Qinghai province were limited thus were not included in the map. (C) Trajectories of the prevalence of obesity and overweight by age. (D) Trends of the prevalence of obesity and overweight. The prevalence was standardized by sex and age. The band indicated 95% CI. (E) BMI z-score of different sexes and ages. Black points indicated the mean of BMI z-score of different groups.

Figure 3

BMI z-score changes during COVID-19 lockdown by province. The changes of the mean BMI z-score in the first half of 2020 and that in 2019.