[Epidemiological characteristics and related factors of multimorbidity of common diseases among children and adolescents aged 7-18 years in Guangdong Province].

<b>Objective:</b> To investigate the multimorbidity of myopia and obesity, as well as myopia and malnutrition, among children and adolescents aged 7-18 in Guangdong Province and analyze their epidemiological characteristics and related factors. <b>Methods:</b> A stratified random cluster sampling method was used to select 274 939 children and adolescents aged 7-18 from 21 cities in Guangdong Province in 2023. Physical examination information such as height, weight, distance vision, and diopter, as well as questionnaire survey information on dietary behavior, physical activity, screen behavior, sleep time, etc., were collected to analyze the current status and trends of multimorbidity between myopia and obesity, myopia and malnutrition. The multivariate logistic regression model was used to analyze the related factors of multimorbidity. <b>Results:</b> The multimorbidity rates of myopia and obesity, myopia and malnutrition in children and adolescents aged 7-18 in Guangdong Province in 2023 were 4.43% and 6.40%, respectively. The multimorbidity rates for males were 5.44% and 6.88%, respectively, which were higher than those for females, about 3.31% and 5.88% (both <i>P</i><0.001). The multimorbidity rates of urban students were 5.03% and 6.73%, respectively, which were higher than those of county students at 4.03% and 6.18% (both <i>P</i><0.001). The multimorbidity rates of myopia and obesity, myopia and malnutrition increased with the increase of academic stage (all <i>P</i><0.001). The multimorbidity rates of myopia and obesity, as well as myopia and malnutrition, fluctuated with age, with the first decrease occurring at the age of 12. The multivariate logistic regression analysis showed that compared to children and adolescents aged 7-18 who had daily after-school tutoring <2 hours, daily screen time <2 hours, did not consume sugary drinks every day, sleep time that could meet health requirements daily, and exercised≥60 minutes of moderate-to vigorous-physical activity ≥60 minutes for at least 3 days per week, those who had daily after-school tutoring ≥2 hours (<i>OR</i>=1.18, 95%<i>CI</i>: 1.11-1.26), daily screen time ≥2 hours (<i>OR</i>=1.09, 95%<i>CI</i>: 1.02-1.16), consumed sugary drinks every day (<i>OR</i>=1.20, 95%<i>CI</i>: 1.11-1.30), daily sleep time that could not meet the health requirements (<i>OR</i>=1.16, 95%<i>CI</i>: 1.09-1.23), and no exercise per week (<i>OR</i>=1.09, 95%<i>CI</i>: 1.01-1.18) had a higher risk of multimorbidity of myopia and obesity. Compared to children and adolescents who exercised≥60 minutes of moderate-to vigorous-physical activity ≥60 minutes for at least 3 days per week, those who exercised <3 days per week (<i>OR</i>=1.20, 95%<i>CI</i>: 1.17-1.34) had a higher risk of multimorbidity of myopia and malnutrition. <b>Conclusion:</b> The multimorbidity rates of myopia and obesity, as well as myopia and malnutrition, in children and adolescents aged 7-18 in Guangdong Province are relatively low and fluctuate with age. Physical activity, screen time, consumption of sugary drinks, and sleep time may be associated with these multimorbidities.