Secular trends of obesity prevalence in urban Chinese children from 1985 to 2010: gender disparity

Abstract

Based on the data from six Chinese National Surveys on Students Constitution and Health (CNSSCH) from 1985 to 2010, we explored the secular trend in the prevalence of obesity in urban Chinese children over a period of 25 years. The aim of this study was to examine the gender disparities in the prevalence of childhood obesity over time. The standardized prevalence of obesity in Chinese children increased rapidly during the past 25 years from 0.2% in 1985 to 8.1% in 2010. The increasing trend was significant in all age subgroups (p<0.01). Although the prevalence of obesity continuously increased in both boys and girls, the changing pace in boys was faster than that in girls. Age-specific prevalence odds ratios (PORs) of boys versus girls for obesity increased over time during the 25 year period. The prevalence of obesity in boys was significantly higher than in girls in all age-specific subgroups from 1991 and after. The gradually expanding gender disparity suggests the prevalence of obesity in boys contribute to a large and growing proportion of obese children. Therefore, it is critical for developing and implementing gender-specific preventive guidelines and public health policies in China.

Figure 1. Age-specific prevalence of obesity and 95% confidence intevals (CI) in the Chinese urban boys (left figure) or girls (right figure) from 1985 to 2010.

Note: In most subgroups, the increasing trends in the prevalence of obesity were statistically significant, and 95%CI of each two adjacent years were not overlapped. In recent five years, there was no significant difference in girls of 13∼15 and 16∼18 year subgroups and boys of 16∼18 year subgroup. The increasing trend was observed in both boys and girls, but the increase values in girls were less than that in boys.

Figure 2. Age-specific prevalence odds ratios (POR) with 95% confidence interval (CI) for obesity of male compared with female in different years of CNSSCH.

Note: In 1985, the 95% CI of POR in 10∼12, 13∼15 and 16∼18 year subgroups included 1, and in 1991, the 95% CI of POR in 13∼15 and 16∼18 year subgroups also included 1, which meant there was no significant differece in gender disparity. The PORs were significant between two genders in other subgroups, and increased over time.