Causality in objective world: Directed Acyclic Graphs-based structural parsing / 中华流行病学杂志

The overall details of causality frames in the objective world remain obscure, which poses difficulty for causality research. Based on the temporality of cause and effect, the objective world is divided into three time zones and two time points, in which the causal relationships of the variables are parsed by using Directed Acyclic Graphs (DAGs). Causal DAGs of the world (or causal web) is composed of two parts. One is basic or core to the whole DAGs, formed by the combination of any one variable originating from each time unit mentioned above. Cause effect is affected by the confounding only. The other is an internal DAGs within each time unit representing a parent-child or ancestor-descendant relationship, which exhibits a structure similar to the confounding. This paper summarizes the construction of causality frames for objective world research (causal DAGs), and clarify a structural basis for the control of the confounding in effect estimate.

Prevalence of alcohol drinking in males aged 20-79 years in China, 2012 / 中华流行病学杂志

Objective: To understand the prevalence of alcohol drinking in 20-79 years old males with different educational backgrounds and smoking behaviors in different areas of China. Methods: A multi-stage cluster random sampling survey was conducted in 150 surveillance sites in 2010-2012 Chinese nutrition and health surveillance in China. At least 1 000 subjects were selected in each surveillance site. Alcohol drinking prevalence and pattern information were collected by using personal health and food frequency questionnaire in face to face interviews. Results: A total of 60 791 males aged 20-79 years were surveyed. The prevalence of alcohol drinking was 57.8% (58.3% in rural area, 57.3% in urban area). The mean daily alcohol intake level was 32.7 g (33.3 g in rural area, 32.1 g in urban area). The rate of almost drinking every day and daily alcohol intake level were highest among males aged 50-59 years. Mean daily alcohol intake level, rate of almost drinking every day and excessive drinking decreased with the increase of education level. Non-smokers had higher rate of never drinking and lower prevalence of drinking and excessive drinking, lower mean daily alcohol intake level, and lower rate of almost drinking every day compared with current and past smokers. Conclusions: Alcohol drinking was common in males aged 20-79 years in China, and, the difference was not obvious between rural residents and urban residents. The differences in daily intake level of different alcohol drinks among males with different characteristics had certain significance. Significant difference in excessive drinking was found among different age groups, those with different education levels and those with different smoking history.

Exposure-preceding-outcome regarding time sequence among cohort studies in real world / 中华流行病学杂志

One of the commonly accepted merits of cohort studies (CSs) refers to the exposure precedes outcome superior to other observational designs. We use Directed Acyclic Graphs to construct a causal graph among research populations under CSs. We notice that the substitution of research population in place of a susceptible one can be used for effect estimation. Its correctness depends on the outcome-free status of the substituted population and the performance of both screening and diagnosis regarding the outcomes under study at baseline. The temporal precedence of exposure over outcome occurs theoretically, despite the opposite happens in realities. Correct effect estimate is affected by both the suitability of population substitution and the validities of outcome identification and exclusion.

Relationship between meat consumption and metabolic syndrome in adults in China / 中华流行病学杂志

Objective: To explore the relationship between meat consumption and metabolic syndrome (MS) in Chinese adults aged ≥18 years. Methods: The data were obtained from 2010- 2012 National Nutrition and Health Survey. A total of 34 923 subjects who completed the dietary survey, the physical examination and had the testing results of blood sugar and blood lipid levels were enrolled in this study. MS was defined according to the diagnostic criteria of China Diabetes Society 2013. The prevalence ratios of MS and each form of MS and related 95%CI were calculated after post stratification weight according to the population data (2009) released by the national bureau of statistics. Results: The average meat intake among subjects was 94.8 g/d. People who had meat consumption between 100 g/d and 199 g/d had the lowest prevalence of MS, abdominal obesity and hyperglycemia. As the meat consumption increased, the prevalence of MS in men increased. Men who had meat consumption of ≥300 g/d had a higher risk of MS than those who had low level of meat consumption, with prevalence ratio equaled to 1.46 (95%CI: 1.14~1.87). Similar trend was not observed in women. Conclusion: Moderate intake of meat is associated with reduced risk of MS in Chinese adults.

The drinking status and associated factors in adults in China / 中华流行病学杂志

Objective: To investigate the drinking status and associated factors in adults in China. Methods: Based on the 2010-2012 China National Nutrition and Health Survey (CNNHS), a total of 135 824 participants aged ≥18 were included in this cross-sectional analysis. Multivariable logistic regression model was used to investigate the associated factors for drinking status. Results: The overall drinking rate was 30.5% in Chinese adults, 53.8% in men, and 12.2% in women. The excessive drinking rate was 14.0% in men and 1.1% in women. The daily drinking rate was 25.7% in men and 10.9% in women. Men mainly consumed multi-type wines, but women preferred beer. The overall harmful drinking rate was 7.1%. The excessive drinking rate, daily drinking rate, and harmful drinking rate increased first but then declined with age. All the four rates were positively related with physical activity. Conclusions: The drinking rate, excessive drinking rate, daily drinking rate and harmful drinking rate were high in adults in China. Drinking status was associated with age, sex, marital status, education level, smoking status and physical activity.

A structural classification of strategies for confounding control in research design / 中华流行病学杂志

Confounding affects the causal relation among the population. Depending on whether the confounders are known, measurable or measured, they can be divided into four categories. Based on Directed Acyclic Graphs, the strategies for confounding control can be classified as (1) the broken-confounding-path method, which can be further divided into single and dual broken paths, corresponding to exposure complete intervention, restriction and stratification, (2) and the reserved-confounding-path method, which can be further divided into incomplete exposure intervention (in instrumental variable design and non-perfect random control test), mediator method and matching method. Among them, random control test, instrumental variable design or Mendelian randomized design, mediator method can meet the requirements for controlling all four types of confounders, while the restriction, stratification and matching methods are only applicable to known, measurable and measured confounders. Identifying the mechanisms of confounding control is a prerequisite for obtaining correct causal effect estimates, which will be helpful in research design.

Prevalence of alcohol drinking and influencing factors in female adults in China, 2010-2012 / 中华流行病学杂志

Objective: To understand the prevalence of alcohol drinking and influencing factors in female adults in China. Methods: At the 150 survey sites where 2010-2012 Chinese nutrition and health surveillance was conducted, a face to face questionnaire survey was conducted in female adults selected through multi-stage stratified cluster random sampling. Sample weights was assigned to each participant based on the study design by using national population census data in 2009. The complex sampling and unconditional multivariate logistics regression analysis was conducted to identify the influencing factors for the prevalence of alcohol drinking in the female adults. Results: A total of 75 518 participants were included in this study. The prevalence of drinking in female adults was 13.9% (95%CI: 11.7-16.2) in urban area and 13.3% (95%CI: 9.4-17.2) in rural area. The prevalence of frequent drinking was 13.9% (95%CI: 9.9-17.9) in women in urban area and 14.2% (95%CI: 10.8-17.6) in women in rural area. The prevalence of excessive drinking was 11.1% (95%CI: 7.5-14.8) in women in urban area and 12.8% (95%CI: 9.1-16.4) in women in rural area. The prevalence of wine drinking in women in urban area was significantly higher than in women in rural and had positive correlation with income and education levels. The social and economic factors influencing drinking behavior of the female adults included occupation, drinking behaviors of family members and smoking behavior. Those who were engaged in agriculture, production and transportation (OR=0.72, 95%CI: 0.56-0.94, P=0.016), housework (OR=0.59, 95%CI: 0.44-0.78, P<0.001) and other work (OR=0.61, 95%CI: 0.43-0.85, P=0.004) had lower drinking prevalence. Whereas those whose family members had drinking behavior (OR=2.66, 95%CI: 2.17-3.26, P<0.001) and those who were current smokers (OR=4.32, 95%CI: 2.95-6.34, P<0.01) had higher drinking prevalence. Conclusions: The prevalence of drinking, frequent alcohol drinking and excessive drinking were relatively low in female adults in China. Occupation, drinking behaviors of family members and smoking behavior were the main factors influencing the prevalence drinking behavior in female adults in China.