【Objective】 To analyze the association of sexual development characteristics and phases with the cognitive and behavioral development of adolescents aged 10 to 14 in rural areas of Shaanxi Province, in order to provide scientific reference for enhancing adolescent health. 【Methods】 The study population was selected from a birth cohort study′s follow-up data for the adolescent phase. The Tanner quintile method was used to assess sexual development, the Wechsler Intelligence Scale for Children, Fourth Edition (WISC-Ⅳ) was used to assess cognitive development, and the Youth Self-Rating Scale(YSR-2001) was used to assess behavioral development. Generalized linear models was used to examine the association of the stages of adolescent sexual development with their cognitive and behavioral development. 【Results】 A total of 1 887 adolescents were enrolled in this study, with 1 111 (58.9%) boys. The proportion of boys and girls who have started sexual development was 78.22% and 89.30%, respectively. The detection rate of behavioral problems in adolescents was 9.70%, with 11.80% in boys and 6.70% in girls, and the gender difference was significant (χ²=13.517, P<0.001). Compared to adolescents in Tanner stage Ⅰ, adolescents in stage Ⅲ had a higher total cognitive score of 2.19 (95%CI: 0.15 - 4.23), and a higher total score of 3.84 (95%CI: 0.85 - 6.83,P<0.05) in stages Ⅳ-Ⅴ. The detection rate of total behavioral problems of children in Tanner stages Ⅳ-Ⅴ was 2.63 times (95%CI:1.27 - 5.46,P<0.05) higher than that in stage Ⅰ. In boys, the rate of detection of internalizing problems was 3.96 times(95%CI:1.60 - 9.81,P<0.01) higher than that in stage Ⅰ, and the detection rate of internalizing problems was 2.88 times(95%CI:1.19 - 7.01,P<0.05) higher than that in stage Ⅰ. 【Conclusions】 There is a significant correlation of sexual developmental phrase with cognitive and behavioral development among adolescents aged 10 - 14 years in rural Shaanxi Province. The detection rate of adolescent behavioral problems increases with the increase of sexual development level and cognitive level, and there are significant gender differences.

【Objective】 To explore the impact of intrapartum antibiotic prophylaxis (IAP) on antibiotic resistance genes (ARGs) in the gut microbiota of infants up to 6 months of age and their longitudinal changes, in order to provide theoretical basis for the rational use of antibiotics and antibiotic resistance control. 【Methods】 Fecal samples were collected within 3 days, 2 months, and 6 months from a maternal and birth cohort conducted between January 2018 and June 2019. A panel of 6 common ARGs (aac(6′)-Ib, qnrS, blaTEM, ermB, mecA, tetM) were tested, the absolute abundance and positive detection rate by qPCR were calculated. Nonparametric and linear mixed model (LMM) analysis were used to assess the influence of IAP on the absolute abundance of antibiotic resistance genes and the longitudinal changes in their abundance at the three time points. 【Results】 A total of 157 samples from 65 singleton infants were analyzed, including 15 mothers (23.1%) who received IAP. The detection rate of ARGs was high in infants up to six months of age, and the abundance of ARGs tended to increase over time. IAP significantly increased the abundance of the mecA gene in the gut microbiota of vaginally delivered infants at 6 months of age (6.1±1.1 in the VDIAP group vs. 3.8±4.6 in the VDno-IAP group, P=0.046). Additionally, in cesarean section infants, there was a significant increase in the abundance of aac(6′)-Ib genes at 2 months (β=3.81, ,P<0.05), P<0.05] and 6 months of age (β=4.89, ,P<0.001), P<0.001) compared to 3 days of age. 【Conclusions】 The findings suggest that IAP can increase the abundance of ARGs in 6-month-old infants, and this effect is still significant after stratifying by delivery mode. Therefore, the rational and standardized use of intrapartum antibiotics may help reduce the development of antibiotic resistance.

【Objective】 To assess the prevalence of chronic diseases and associated influencing factors among residents in Ali so as to provide reference for local prevention and control of chronic diseases. 【Methods】 Stratified cluster random sampling was used to investigate the prevalence of chronic diseases and their influencing factors among permanent residents over 18 years of age in Aili. 【Results】 Totally 606 subjects were included, with a prevalence of chronic diseases of 39.93% and the highest prevalence of rheumatoid arthritis of 14.03%. The prevalence of chronic diseases was significantly different among ethnicity, age, education, occupation, personnel category, family living standard, amateur physical exercise, fuel type and self-rated health (P<0.05). Logistic regression showed that the risk of chronic diseases among the residents aged 50 years and above was 2.656 (95% CI: 1.439-4.901) times higher than that of residents under 30 years; the risk of chronic diseases among the residents with elementary school education and below was 3.528 (95% CI: 1.519-8.197) times higher than that of residents with college education and above; housework personnel could reduce the risk of chronic diseases (OR=0.365, 95% CI: 0.161-0.828); residents with poor self-rated health had 5.814 (95% CI: 3.243-10.423) times higher risk of chronic diseases than those with good self-rated health; and those with a weight gain of more than 2.5 kg in the past year could increase the risk of chronic diseases (OR=2.029, 95% CI: 1.226-3.358). 【Conclusion】 The prevalence of chronic diseases is high in residents of Ali. Attention should be paid to the elderly population with poor self-rated health and tendency of weight gain. Personalized behavioral lifestyle health education is helpful in preventing the occurrence of chronic diseases.

Cohort study is one of the important research methods in analytical epidemiology because of its clear time sequence relationship, which is better than other observational studies in demonstrating causal association. However, screening diagnosis or other methods are often used to exclude the individuals with outcome events during the enrollment process of the subjects in cohort studies. The accuracy of screening diagnosis and the effectiveness of exclusion will affect the accuracy of the baseline status assessment of the subjects included in the study, which may lead to the causal time sequence reversal of exposure-outcome in the estimation of causal effect. Landmark analysis can be used to control reverse causality by excluding subjects with potentially unknown expose-outcome timing. In this paper, we describe the basic principles and analytical steps of landmark analysis, and use data from the Chinese Longitudinal Healthy Longevity Survey to explore the relationship between physical activity and frailty, and introduce the specific application of landmark analysis for the purpose of facilitating its application and inferring causal effects more accurately in cohort studies.

With completing a baseline survey of a large natural population cohort, conducting regular follow-up has become a key factor in further improving the quality of cohort construction and ensuring its sustainable development. Typical cohort follow-up methods include repeat surveys, routine monitoring, and community-oriented surveillance. However, in practical applications, there are often issues such as high costs, difficulty, and high error rates. Telephone follow-up is an important supplementary method to the methods mentioned above, as it has the characteristics of low cost, fast response, and high quality. However, the with difficult organization, quality control is challenging, response rates are low, and management levels vary widely, which limits its widespread use in large-scale population cohort studies. Given the above problems, this study draws on customer relationship management based on the actual needs of the China Northwest Cohort follow-up. It relies on the REDCap electronic data collection platform to build a telephone follow-up management and quality control system. Targeted solutions are provided for key issues in telephone follow-up implementation, including organizational structure, project management, data collection, and process quality control, to improve the quality control level of telephone follow-up comprehensively and thereby enhance the quality and efficiency of follow-up. We hope to provide standardized follow-up programs and efficient quality control tools for newly established and existing cohort studies.

【Objective】 To explore the dynamic change of depression in diabetic patients so as to provide evidence for early detection and warning of psychological problems in diabetic patients. 【Methods】 Based on the data from the China Health and Retirement Longitudinal Study （CHARLS）， the propensity score matching method was used to eliminate confounding factors in the study. The linear growth model， the nonlinear quadratic growth model， and the growth model without defined curve type were fitted respectively. According to the fitting indices of the models， the optimal solution of the growth function was determined to explore the changes of depression development in the diabetic patients. 【Results】 A total of 5 711 cases （5 380 cases in the non-diabetic group and 331 cases in the diabetic group） were included in the study. After propensity score matching， 1 621 cases （1 291 cases in the non-diabetic group and 330 cases in the diabetic group） were included and all confounding factors were balanced between the two groups. By fitting three growth curve models with latent variables， the results showed that the model without defined curve type was better than the other two models. The mean depression score for initial status in the non-diabetic and diabetic groups was 9.640 and 10.097， respectively， with significant inter-individual differences. During the follow-up period， the depression status of both groups showed a trend of decrease first and then increase， but the depression score was always lower in the non-diabetic group than in the diabetic group. At the same time， there was no individual difference in the rate of change between the two groups， and there was no statistical difference between the initial depression score and the subsequent slope of change. 【Conclusion】 Exploring the change track of depression status over time in diabetic patients， understanding the individual psychological change trend and further explaining the differences between individuals are of great significance for intervention on psychological status at different stages.

【Objective】 To clarify the hematological characteristics and current situation of chronic mountain sickness among Tibetan residents in extreme high altitude area (more than 5 000 m above the sea level) of Ali district based on the analysis of physical examination and blood test results. 【Methods】 Totally 250 Tibetan residents were selected by convenient sampling for blood oxygen saturation (SpO2), heart rate, and blood routine examination. Chronic mountain sickness was determined according to the hemoglobin (Hb) level and SpO2. 【Results】 The red blood cell (RBC), Hb and hematocrit (HCT) of the Tibetan residents at 5 200-meter altitude were all higher than the normal physiological reference range of China. Mean red blood cell volume (MCV), mean red blood cell hemoglobin content (MCH), mean red blood cell hemoglobin concentration (MCHC), white blood cell (WBC) and platelet (PLT) were in the upper limit of the reference value. The RBC, Hb, HCT and MCHC of male Tibetan residents were higher than those of females, while PLT was lower than that of females, with significant differences. There were no statistical differences in MCV, MCH or WBC among different genders of Tibetan residents. The SpO2 of the Tibetan residents was about 85% of the normal value, and the males had higher SpO2 than the females in the same age group, and the difference was statistically significant, but the heart rate did not differ significantly. The prevalence rate of chronic mountain sickness in this area was as high as 16.4%, and the prevalence rate of heavy manual workers was significantly higher than that of light manual workers, with significant differences. 【Conclusion】 The high-altitude anoxic environment causes the changes in red blood cells, hemoglobin, and oxygen saturation of local residents, and the prevalence of chronic mountain sickness increases significantly. Labor intensity is one of the risk factors for chronic mountain sickness in high-altitude areas.

【Objective】 To evaluate the diet quality of pregnant women in Shaanxi Province by Diet Balance Index for Pregnancy (DBI_P) and investigate the influencing factors. 【Methods】 By using a multi-stage stratified random sampling method, 7375 pregnant women in 30 districts (counties) of Shaanxi Province were recruited. A structured questionnaire was adopted to collect general information in pregnancy, and a semi-quantitative food frequency questionnaire was used to obtain dietary information in pregnancy. DBI_ P was used to evaluate the diet quality during pregnancy, and the factors influencing diet quality were assessed by multiple linear regression. 【Results】 More than 50% pregnant women had inadequate intakes of dairy products, fish and shrimp, meat and poultry, vegetables, eggs, fruits and diet variety. More than 69% pregnant women had excessive intakes of cooking oil, cereals and salt. The average values of high bound score, low bound score, and diet quality distance were 12.9, 19.5, and 32.5, respectively. The proportions of medium inadequate, excessive, and imbalance of dietary intakes were 20.3%, 22.55%, and 40.8%, respectively. DBI_LBS during pregnancy was negatively correlated with childbearing age, education level, family per capita annual income, antenatal examination frequency and folic acid supplementation, but positively correlated with living in southern and northern Shaanxi, residing in rural areas, being farmers, and drinking alcohol. DBI_HBS during pregnancy was negatively correlated with living in southern and northern Shaanxi, but positively correlated with active/passive smoking and drinking strong tea. DBI_DQD during pregnancy was negatively correlated with education level, family per capita annual income, antenatal examination frequency and folic acid supplementation, but positively correlated with living in southern Shaanxi, residing in rural areas, being farmers, parity, active/passive smoking, and drinking strong tea and coffee. 【Conclusion】 The dietary intake of pregnant women in Shaanxi Province was insufficient and unbalanced, and the dietary quality was affected by sociodemographic and life behavior factors during pregnancy. Nutritional intervention measures should be targeted.

Objective:To study the relationship between the Chinese dietary guidelines compliance index for pregnant women (CDGCI_PW) and congenital heart disease (CHD) in offspring.Methods:In a hospital-based case-control study conducted in Xi'an, Shaanxi province, semi-quantitative food frequency questionnaires were used to investigate the diets of pregnant women throughout pregnancy. The modified CDGCI_PW score was used to evaluate dietary quality during pregnancy, logistic regression was applied to analyze the relationship between CDGCI_PW score and offspring CHD, and the ROC curve was adopted to construct the prediction model of CDGCI_PW for offspring CHD.Results:A total of 1 422 subjects were enrolled, including 474 in the case group and 948 in the control group. The CDGCI_PW score in the case group M ( Q1, Q3) was 46.0 (26.0, 65.0) lower than that in the control group, which was 60.0 (40.0, 77.0). The difference between the two groups was significant ( P<0.001). Compared with those in the Q1 of CDGCI_PW, the offspring in the Q2, Q3, and Q4 of CDGCI_PW had a lower risk of total CHD ( OR=0.60, 95% CI: 0.43-0.83; OR=0.64, 95% CI: 0.45-0.89; OR=0.29, 95% CI: 0.19-0.44), with the trend test P<0.001. The risk of total CHD was reduced by 17% ( OR=0.83, 95% CI: 0.79-0.88) when 10 points increased the CDGCI_PW score. The area under curve predicted by constructing the ROC curve was 0.793 (95% CI: 0.768-0.818), and at the maximum of the Youden index, the sensitivity was 0.740, and the specificity was 0.725. Conclusion:This study suggests that improving dietary quality during pregnancy may reduce the risk of CHD in offspring.

【Objective】 To describe the BMI growth trajectories from birth to 24 months and examine the effects of fully breastfeeding time and breastfeeding duration on the BMI growth trajectories. 【Methods】 We conducted a follow-up study of a cohort of 1 388 eligible births. Height and weight were measured at birth, every 3 months to 12 months, and every 6 months to 24 months. Detailed demographic, feeding, activity and diseases data were also collected prospectively. Latent growth mixture modeling was conducted to model the BMI growth trajectories from birth to 24 months. Mixed-effects logistic regression analyses were made to examine the impacts of breastfeeding on this outcome. 【Results】 We identified six BMI trajectory patterns in the 1 285 infants analyzed and labeled them as follows: "normative growth" (26.6%), "normal-accelerating growth" (8.7%), "normal-decelerating growth" (11.7%), "lower-persistent growth" (6.6%), "rapid growth" (26.8%), and "rapid-accelerating growth" (19.5%). Mixed-effects logistic regression analyses revealed that fully breastfeeding ≥ 3 months could significantly decrease the risk of "rapid growth" (OR=0.71, 95% CI 0.51-0.98) and "rapid-accelerating growth" (OR=0.53, 95% CI 0.37-0.75). After adjustment for confounding factors, the relationship remained significant (OR=0.61, 95% CI 0.41-0.89; OR=0.46, 95% CI 0.31-0.68). Weaning before 6 months could significantly increase the risk of "rapid growth" (OR=1.76, 95% CI 1.19-2.61) and "rapid-accelerating growth" (OR=2.08, 95% CI 1.38-3.14). These associations persisted after adjustment for confounding factors (OR=1.69, 95% CI 1.08-2.71; OR=1.88, 95% CI 1.18-2.99). 【Conclusion】 In rural Western China, the main BMI growth trajectory patterns include "normative growth" , "rapid growth" , and "rapid-accelerating growth" . Prolonging breastfeeding may reduce excess weight gain during infancy.