Association between BMI and age at menarche or spermarche among both sexes: Findings from six successive national surveys in China.

Background: To explore trends of the association between body mass index (BMI) and age at menarche or spermarche and its urban-rural disparities from 1995 to 2019. Methods: A total of 912 753 children and adolescents - including 519 940 9-18 years old girls and 392 813 11-18 years old boys - were involved in six successive cross-sectional surveys conducted across 30 provinces in China from 1995 to 2019. Data on menarche and spermarche was collected using the status quo method, where same-gender physicians conducted face-to-face interviews to determine if children and adolescents had experienced their first menstrual cycle or ejaculation (yes/no). The median age at menarche or spermarche was estimated by probit analysis. Anthropometric measurements measured the height and weight of the study subjects. Children and adolescents were classified into thinness, normal range of weight, overweight, and obesity. t test was used to compare the differences in BMI between premenarchal and postmenarchal girls or prespermarcheal and postspermarcheal boys. Logistic regression was used to explore the associations between BMI/nutritional status and menarche or spermarche stratified by urban or rural residency status. Results: From 1995 to 2019, BMI in all age groups growth over time, and the values of BMI among children and adolescents under 15 who had menarche or spermarche were more significant than those without menarche or spermarche. In 2019, for girls, thinness was associated with delayed menarche (odds ratio (OR) = 0.26; 95% confidence interval (CI) = 0.24-0.28), while overweight (OR = 1.99; 95% CI = 1.85-2.14) and obesity (OR = 2.20; 95% CI = 1.92-2.53) was associated with advanced menarche. For boys, thinness was associated with delayed spermarche (OR = 0.71; 95% CI = 0.65-0.78), overweight was associated with advanced spermarche (OR = 1.08; 95% CI = 1.01-1.15) while obesity had no association with spermarche. The OR between BMI and menarche in 1995 was 1.35 (95% CI = 1.33-1.37), which decreased to 1.19 (95% CI = 1.18-1.20) by 2019. The OR between BMI and spermarche in 1995 was 1.10 (95% CI = 1.09-1.11), which decreased to 1.02 (95% CI = 1.02-1.03) by 2019. The trends by urban-rural stratification were consistent with the total sample. Conclusions: We have established a dose-response relationship between BMI and menarche in girls, whereas the association appears to be nonlinear in boys, and the associations were diminishing. Similar findings were observed in both urban and rural areas. Considering the dual adverse effects of obesity and early puberty on health, the results of this study suggest that sexual health education should be strengthened, especially among obese girls. Further research on the influencing factors and biological mechanisms of early puberty will be beneficial.

The effect of equalization of public health services on the health China's migrant population: Evidence from 2018 China Migrants Dynamic Survey.

Objectives: China has implemented an equalization of public health Services policy for migrants in 40 pilot cities since 2013. The main objective of this study is to explore the effect of this migrant-based reform policy on the health status of the migrant population in China. Methods: Using the China Migrants Dynamic Survey (CMDS), we included 152,000 migrants aged 15 years or over in 2018. Standardized questionnaires were used to collect socio-economic information and self-reported health status. The Associations between the equalization of public health services and health status were estimated using Multiple regression estimation models and Propensity Score Matching (PSM) methods. Results: Public health equalization reform in China has a significant and positive effect on the health status of the migrant population (ß = 0.033, p < 0.001). Compared to males, higher income, under 60 years of age, inter-provincial mobility, and migrants those already living in urban areas, the equalization of public health Services had shown more significant positive effects on the groups who were inter-provincial migration (ß = 0.055, p < 0.001), females (ß = 0.055, p < 0.001), having low-income (ß = 0.077, p < 0.001), aged over 60 years old (ß = 0.191, p < 0.001), and living in rural areas (ß = 0.038, p < 0.001). And multiple robustness tests prove that the above results are reliable. Conclusions and implications: Our findings confirmed the positive health effect of the equalization of public health services reform on china's migrant population, especially among vulnerable groups such as those in low income groups, in rural areas and females. And we recommend that it is necessary to further promote the practices and experiences of the pilot cities. First, strengthen health education for the mobile population and improve their health literacy. Second, further increase the financial investment to improve the coverage of public health services and the equity in resource allocation among regions. Last, strengthen the information-based management of the migrant population and prevent and control infectious diseases.