流行病学英文版总结（精华版）
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1、Epidemiology
Epidemiology is the study that is based on distribution and factors of diseases and health-related states in populations,and then makes politicies and takes measures to control heslth problems.
2、Exposure
Exposure is a very common used term in epidemiology,it refers to the causal factors that may be associated with the disease,for example,contact with    a harmful materials,or some characteristics ,such as the age which may put an individual at increased risk.
3、Outcome
Outcome is the disease or other changes in health status.It is the possible result that may be associated with the causes,risk factors or preventive measures.
4、Descriptive epidemiology
Descriptive epidemiology is concerned with the variations of morbidity and mortality in a community.It concentrates on the description of distribution of morbidity or mortality by person,place and time,and then we can pose the hyposthesis,such as case report,ecological study and cross-sectional study.
5、Ecological study
Ecological study is a type of descriptive study.It is the study of the relationship between some factors and diseases in the group level, the unit of observation and analysis is group.We describe the exposure status of disease factors and the frequency of diseases in different populations and then analyse the relationship between exposure and disease,for example, ecological comparison study and ecological trend study.
6、Experimental epidemiology
Experimental epidemiology is to identify a group of subjects with the same conditions,and randomizes the subjects into intervention and control groups,follows them up for a period of time,compares the outcome between the groups,so as to evaluate the efficacy of the intervention.It is also called the interventional study,includes clinical trial,field trial and community trial.
7、Observational study
Observational study is a kind of epidemiology.We observe and measure the occurrence of the disease or other health-related status in different groups with various characteristics and attempt to identy the causal association between the exposure and outcome,but we do not intervene in any way,so it is called the observational study,such as cross-sectional study,cohort study and so on.
8、Three levels of prevention
Primary prevention concentrates on the cause prevention or reduction of risk factors,so as to prevent the development of disease.
Secondary prevention is to diagnose and treat diseases in their early stages so as to restore or improve health,such as the screening program.
Tertiary prevention is to reduce complications of disease,improve the outcome,so as to improve the quality of life of the patients.
9、PYLL
PYLL is measure of the socio-economic impact of the premature death of an individual.It is
measured by deducting the age of death from the life expectancy of the individual.
10、Incidence
Incidence measures the rate of occurrence of new cases of disease in a given population in a given time and can be used to describe the risk of disease in that population.
(number of new cases/population)
10、Prevalence
Prevalence measures the rate of occurrence of both new and ongoing cases of diseases in a given population,in a given time,and can be used to describe the burden of disease in that population,includes point prevalence and period prevalence.
(number of existing cases/population at risk)
11、Cross-sectional study
Cross-sectional study is a type of descriptive study,is also called prevalence study.It is an investigation that systematically collects information in a given time and does not use intervention.It concentrates on description of the distribution of prevalence rate by person,place,and time,and then we can pose the hyposthesis.
12、Bias
Bias is a systematic error ,it exsits in the design ,conduct or analysis of a study and it may result in a mistaken estimate of the association between the exposure and outcome,such as selection bias,information bias,confounding bias.
13、Confounding bias
Confounding variable is an extraneous factor that relates(positively or negatively)with both the outcome and the tentative factor of study ,and may result in a mistaken estimate of an exposure effect on the risk of disease.And the bias which is caused by the confounding variable is called confounding bias.
14、Screening
Screening is the early detection and presumptive identification of an unrecognized disease or deficit by application of examinations or tests which can be applied rapidly and cheaply to large populations.
15、Cohort study
Cohort study is a kind of observational study.The investigator selects a group of exposed individuals and a group(or groups)of non-exposed individuals,and follows up both groups for a period of time,to compare the incidence of disease or the death rate of the disease in the two groups(or more groups)and measure the association between the exposure and the outcome.It is also called a prospective study or follow-up study.
16、Case-control studies
Case-control studies start with the identification of people with the disease of interst and a control group of people without this disease ,then collect some information of the exposure in both groups,and measure the association between the exposure and the disease by comparing the diseased and non-diseased group.It is a kind of observational study ,and it is also called the retrospective study.
17、Matching
Matching is defined as the process of making a study group and a comparison group comparable with respect to certain characteristics,such as sex,age,race and so on.The puepose of matching is to reduce the likelihood of confounding,includes individual matching and frequency matching.
18、OR
OR is a very useful measure for the association between exposure and outcome.It is the ratio of the odds of exposure among the cases to the odds of exposure among the controls.The more the or departs from one,the greater the association between the exposure and outcome.
19、RR
RR is the most common measure for the association between esposure and outcome.The meaning is how many times the risk of exposed people is that of unexposed.
If RR=1 it means the risk in exposed group and unexposed group are equal ,there is no association between the exposure and the outcome.
If RR>1 it means the risk in exposed group is greater than the unexposed group,there is a positive association between the exposure and the outcome.
If RR<1 it means the risk in exposed group is less than the unexposed group,there is a negative association between the exposure and the outcome.
20、AR
AR is a very important and commom measure for the effect of the exposure.It is the difference of the risks between the exposed group an unexposed group.The AR can be interpreted as the risk caused by the exposure only,or the risk attributable to the exposure.
21、Cause
Cause may indicate that the factors that may increase the probability of the disease and that a diminution of one or more of these factors may decrease the frequency of that disease.
22.Case Control & Cohort Study Differences
Case Control Studies Cohort Study
Advantages They are quicker and inexpensive to conduct It can measure the incidence of
disease,so it can tmeasure RR They are good for rare diseases It good for rare exposures
The sample size is smaller than cohort study It is prospective and permits
multiple outcomes to be
assessed in the same study
They are good for new serious diseases to explore the possible causes The temporal sequence is appropriate,so it good for causal association inference
Disadvantages They are retrospective,temporal sequence may
be a problem,so it is difficult to establish the
association between exposure and diseases It requires large sample sizes and need long follow-up periods
There are some potential biases,such as
selection bias,recall bias
It is very expensive
They can not measure the incidence of disease,therefore can not measure RR It is inefficient for rare diseases
They are iefficient for rare exposures Some biases:loss to follow-up
bias,measurement bias
23、Molecular epidemiology
Molecular epidemiology is a branch of epidemiology.It combines theories and methods in both epidemiology and molecular biology.The definition of molecular epidemiology is its use of biological and genetic markers as a measure of the prospensity of developing a disease or as an indicator of a disease or all exposure in the studies of the distribution and causes of disease. Molecular epidemiology has the same objectives as conventional epidemiology,to study the occurrence,development and prognosis of disease,to evaluate the effectiveness of interventions,and to provide evidence for clinical and healthcare decision making in a defined population.
References：
（（1）李立明主编.流行病学.第6版.北京：人民卫生出版社.2007
（2）赵仲堂主编.流行病学研究方法与应用.第2版.北京：科学出版社,2005
xposed
（3）Wang Peishan.Epidemiology An Introduction for Medical Students.Tianjin:Tianjin Science and Technology Translation Publishing Company,2011
（4）Rothman KJ. Epidemiology:An Introduction.New York:Oxford University Press,2002 （5）方积乾主编.卫生统计学第6版.北京：人民卫生出版社.2007
（6）颜虹主编.医学统计学第2版.北京：人民卫生出版社.2010
（流行病学和卫生统计学两部分，以流行病学为主，由于水平有限，时间有限，存在各种问题不可避免，还望指出纠正！）
乌衣月
2013年4月13日