Objective To explore the application of segmented linear regression of interrupted time series design in the evaluation of policy intervention and SAS implementation, and to provide reference for public health policy researchers in methodology application. Methods Taking the influence of the two-child policy on the cesarean section （CS） rates as an example, SAS software was used for the segmented linear regression model in the CS rates at Ⅳ-class maternity hospitals in Guangzhou between January 2013 to December 2016, including principle of the model, SAS program, controlling for autocorrelation and adjustment of covariates. Results The segmented linear regression analysis showed that there was no significant change in the level and trend of CS rate at Ⅳ-class maternity hospitals in Guangzhou both during the period of the selective two-child policy and the universal two-child policy after adjusting maternal age and the history of CS. Conclusion The segmented linear regression model is a powerful tool for evaluating the effects of policy by estimating the changes in the level and trend of observed indicators before and after the intervention, but attention should be paid to the applicable conditions and the interpretation of the results for its limitations.

Objective To investigate the cadmium content of main food sold in Guangzhou, and to preliminarily evaluate the health risk of the children and adolescents aged 3-17 years exposed to cadmium via the diet. Methods The cadmium content of 2 882 foods of 16 categories in Guangzhou was determined from 2016 to 2018. Combined with the data of food consumption survey of Guangzhou in 2011, the cadmium exposure risk of children and adolescents aged 3-17 years was preliminarily evaluated by the point estimate method. Results The average content of cadmium in major foods sold in Guangzhou was 0.000 4 -1.397 5 mg/kg. The total detection rate was 81.37%. The average cadmium content of bivalves was the highest （ with the average of 1.397 5 mg/kg）. The average monthly cadmium dietary exposure was 17.129 5 µg/kg·BW for preschool children aged 3-6 years, and 13.970 9 µg/kg·BW for school-age children and adolescents aged 7-17 years, both of the margin of safety （MOS） were greater than 1. According to high exposure model of food chemicals, the high-end exposure （95th percentile） of each group was 43.018 2 and 39.812 7 µg/kg·BW respectively, with the MOS less than 1. With the average dietary consumption of children and adolescents aged 3-6 years and 7-17 years, the main sources of cadmium exposure were rice and its products, leaf vegetables and bivalves, and the cumulative contribution rates of three kinds of food were 72.39% and 75.09%, respectively. With the high dietary consumption, the major sources of cadmium were bivalves, rice and its products and leaf vegetables, and the cumulative contribution rates of three kinds of food were 89.01% and 91.27%. Conclusion The cadmium intake of children and adolescents aged 3-17 years in Guangzhou through the daily diet is of low risk to health. However, children with high dietary consumption, especially those with high intake of bivalves have certain health risks. It is necessary to strengthen the monitoring of cadmium content in key food and advocate a balanced diet and diversity of food intake.

Objective To investigate the current situation of violence among patients with severe mental disorders in Hainan Province and analyze its influencing factors. Methods Taking the cases of severe mental disorders in Hainan Province as the research object, the risk level assessment was completed during the follow-up of the cases in charge in 2019. The basic information of the cases and the disease-related factors were derived from the information management system of severe mental disorders in Hainan Province. Descriptive epidemiological analysis method was used to analyze the occurrence of severe violence among the cases of severe mental disorders, and univariate and multivariate analysis methods were used to analyze the influencing factors of severe violence. Results In 2019, a total of 29 054 registered cases of severe mental disorders were followed up and their risk assessment was completed. The age of the cases was 15-95 years, with an average age of （39.87±16.54） years. The Han nationality accounted for 87.66%. The main diseases were 18 760 cases of schizophrenia （64.57%）, 4 273 cases of bipolar affective disorder （14.71%）, 4 157 cases of mental retardation with mental disorders （14.31%）. The evaluation results showed that there were 1 756 cases of severe mental disorders with severe violence, and the incidence rate was 6.04%. Mainly grade 3, accounting for 68.23% （1 198 cases）. Multivariate Logistic regression analysis showed that the patients with severe mental disorders aged 18 to <45 （OR=1.264）, 45 to <60 （OR=1.099）, were unemployed （OR=1.697）, with the more times of previous hospitalizations （OR=2.282）, the more times of previous emergency treatments （OR=3.360）, no antipsychotic treatment （OR=5.989）, risky behavior before file establishment （OR=7.815）, the onset form was subacute （OR=1.260） or acute （OR=1.575） were more likely to have severe violence. Conclusion The incidence of severe violence is relatively high among patients with severe mental disorders, and it can effectively prevent the occurrence of violence to carry out classification management according to the relevant risk factors as soon as possible.

Objective To study the influencing factors of hysteromyoma and guide the related prevention and treatment. Methods Taking the cases of hysteromyoma diagnosed for the first time in a hospital in Panzhihua from February 2020 to January 2021 as the case group, according to age ±0.05 years, BMI ±0.05 and a ratio of 1：1 to select women without hysteromyoma who undergoing physical examination at the hospital physical examination center in the same period as the control group. Questionnaire survey was conducted, including age, height, weight, abortion history, childbearing history, menstrual irregularity, gynecological inflammation, endometriosis, family genetic history, anxiety, depression, physical exercise, sleep duration, long-term （> 6 months） oral contraceptives, etc. Univariate and multivariate analysis methods were used to analyze the related factors of women with or without hysteromyoma. Results The survey data of 551 patients with hysteromyoma and 563 women without hysteromyoma were complete. In the case group, the age was mainly 46-59 years old, accounting for 45.37%; and the BMI was mainly 18.5-23.9, accounting for 57.35%; 23.41% had abortion history and 73.50% had childbearing history. In the control group, 41.56% were 46-59 years old, 58.61% were BMI 18.5-23.9, 16.52% had abortion history and 70.34% had childbearing history. There were no significant differences in age, BMI, childbearing history, endometriosis, physical exercise and sleep duration between the two groups （all P>0.05）. Multivariate Logistic regression analysis showed that abortion history （OR=1.468）, menstrual irregularity （OR=1.273）, gynecological inflammation （OR=1.562）, family history of disease （OR=1.487）, anxiety （OR=1.996）, depression （OR=2.474） and long-term oral contraceptives （OR=2.223） were risk factors for the onset of hysteromyoma. Conclusion Hysteromyoma is affected by many factors such as abortion history, menstrual irregularity, gynecological inflammation, family history of disease, anxiety, depression, long-term oral contraceptives. Women should be guided to maintain a good psychological state, avoid abortion, and attention to reproductive system health to reduce the incidence of hysteromyoma.

Objective To investigate the correlation between dietary nutrients intake and physical health of students in a junior middle school in Fangshan District of Beijing, and to provide basis for improving physical health status of teenagers. Methods By cluster sampling method, students of 3 grades in a junior middle school in Fangshan District of Beijing were selected for physical health test, 3-day 24-hour dietary review survey, and questionnaire survey on knowledge, attitude and practice （K-A-P） of nutrition. Results A total of 181 students were effectively investigated, including 92 girls （50.83%） and 89 boys （49.17%）. The control rate of physical health of students in this junior middle school was 34.81%, and the gender difference was statistically significant （Ρ<0.05）. The intake of dietary nutrients among students whose physical health reaching standard was good, but the daily average intake of calcium just accounted for 43.74% of recommended nutrient intake （RNI）. The 9 dietary nutrients intake of students whose physical health not reaching standard all less than the students reaching standard, and the differences were statistically significant （all Ρ<0.05）. The daily average intake of vitamin A and calcium among students whose physical health not reaching standard was below 30% of RNI, protein, vitamin B₂, vitamin C, zinc, selenium and ferrum just accounted for 40%~60% of RNI. The questionnaire scores of K-A-P of nutrition among students whose physical health reaching standard were better than those not reaching standard, and the difference was statistically significant （Ρ<0.01）. Pearson correlation analysis showed that the intake of protein （r=0.706, Ρ<0.01） and calcium （r=0.636, Ρ<0.01） strongly correlated with physical health. Conclusion The physical health of the junior middle school students in Fangshan District of Beijing was poor, and there was a statistical correlation between the dietary nutrients intake and physical health. It is suggested that the physical health of students should be enhanced by reasonable diet.

Objective To investigate the status of electronic health （e-Health） literacy among college students in Guangdong Province during the COVID-19 epidemic, and to explore the influencing factors, so as to provide a basis for further improving the e-Health literacy of college students. Methods Web-based questionnaire survey was used among college students in Guangdong Province. Results A total of 16 497 valid questionnaires were collected,including 11 268 girls（68.3%）.There were 7 241 students （43.9%）, 4 467 students （27.1%）, 2 842 students （17.2%） and 1 947 students （11.8%） in freshmen, sophomore, junior and seniors respectively, with 5 769 students （35.0%） in liberal arts among all disciplines.The average score of e-Health literacy was （29.62±6.74）, with a qualified rate of 23.6%. Multivariate analysis showed that the students having higher e-Health literacy were medical majored（β’=0.053）, currently in Guangzhou or Shenzhen（β’=0.030）, having more information sources（β’=0.037）, having more approaches to judge the reliability of online information （β’=0.034）,having more concern about COVID-19-associated information（β’=0.118）,having more knowledge of COVID-19（β’=0.233）; And the students having lower e-Health literacy were female（β’=-0.039）,the more the confusion caused by pandemic-related information（β’=-0.069）. Conclusion E-Health literacy ability of college students in Guangdong Province is relatively low. Improving e-Health literacy can not only improve their ability of judging and acquiring health information, but also raise the awareness of the epidemic.

Objective To analyze the status of dental caries among preschoolers in Nanchong City and explore its related factors, so as to provide reference for prevention and treatment of dental caries in preschoolers in Nanchong City. Methods In October 2020, four kindergartens were selected from three districts and one county-level city under the jurisdiction of Nanchong City. All preschoolers in the selected kindergartens were surveyed for dental caries and conducted oral examinations. The main guardians of the children were investigated by questionnaire on the eating habits and oral health care behaviors. Descriptive epidemiological analysis method was used to analyze, and univariate and multivariate analysis methods were used to analyze the influencing factors of dental caries in preschoolers. Results This study conducted a total of 1 026 preschoolers, boys accounted for 51.6%, aged 3 to 6 years old, with an average of （4.1±1.4） years old. The time to start brushing was mainly under 3 years old, accounting for 67.6%. A total of 341 preschoolers with dental caries were detected, and the prevalence rate was 33.2%. A total of 527 dental caries were detected, among which 243 dental caries were upper and lower deciduous molars, accounting for 46.1%; 195 dental caries were upper and lower deciduous incisors, accounting for 37.0%; and 89 dental caries were upper and lower deciduous canine teeth, accounting for 16.9%. Multivariate Logistic regression analysis showed that the preschoolers with older age （OR=2.361）, the frequency of eating sweets> 6 times/week （OR=2.951）, and the time to start brushing ≥ 3 years old （OR=1.674） were at higher risk of dental caries, preschoolers who rinsed their mouth after meals frequently （OR=0.824）, brushed their teeth in the morning and evening （OR=0.424）, used fluoride toothpaste frequently （OR=0.410）, and had regular oral examinations （OR=0.692） were at lower risk of dental caries. Conclusion Dental caries is common among preschoolers in Nanchong City, which is affected by many factors such as eating habits and oral health care behavior. It is necessary to increase the publicity of oral health education, improve the awareness of oral health care of preschoolers, and urge them to establish a good diet and oral health care behavior.