1、1,描述性研究,Descriptive Study,哈尔滨医科大学流行病学教研室 Department of epidemiology ，Harbin Medical University,2,Methods of study,Observational,Experimental,Theoretical,Descriptive study,Analytic study,Clinical trial Field trial Community intervention,three types of basic methods,Case-control study Cohort study,Cro
2、ss-sectional study Ecological study,3,Epidemiology is the study of the distribution and determinants of disease frequency in human population. Epidemiology: Principles and Methods by Brian MacMahon 1996,4,?,The distribution of Disease considers,Who is getting disease?Where is disease occurring?When
3、is disease occurring?,5,Person,Place,Time,Cases,Descriptive Epidemiology,Who? Where? When?,6,Descriptive study is to subset collected data or some survey data, included the data from experiment, to groups by different places, different time or different population character and descriptive the frequ
4、ency of disease and health. Helps to build the relationship between risk factors and disease or health, offer etiological clues.,描述性研究通过描述疾病或健康状况的三间分布情况，找出某些因素与疾病或健康状况间的关系，提供病因线索。,7,目 录,现况研究的概述现况研究的设计与实施 研究实例 生态学研究,Introduction of cross-sectional study Design and implementation of cross-sectional st
5、udy A case study Ecological study,Outline,8,第一节 现况研究概述 Introduction of Cross-sectional Study,基本概念 目的与应用特点与类型,Basic conceptMechanism Purposes and applications Characteristics and categories,9,一、基本概念 Conception,又称横断面研究也称患病率研究时点或期间和特定范围内人群中的有关变量(因素)与疾病或健康状况的关系,Cross-sectional study or prevalence study
6、Describes the relationship between disease or health and variables (factors) in the population at a particular point of time or period,10,Time,11,Schematic diagram of Cross-sectional Study,12,掌握目标群体中疾病或健康状况的分布提供疾病病因研究的线索,二、目的与应用Mechanism Purposes and applications,Describes the distributing of diseas
7、e or health events within populationsTo provide etiological clues,13,This figure shows the infant death frequency (per 1000 live births) in different countries,14,确定高危人群 评价疾病监测、预防接种等防治措施效果,二、目的与应用Mechanism Purposes and applications,To identify high risk groups in the populationTo evaluate the effect
8、 of surveillance，vaccination and disease prevention and control,15,研究特点 开始时一般不设对照组 现况研究的特定时间 在确定因果联系时受到限制 对不会发生改变的暴露因素，可以提示因果联系,三、特点与类型 Characteristics and categories,Characteristics No control group Particular point of time Limit to ensure the causal relationship To prompt causal relationship for t
9、he exposures that wont be changed,16,研究类型 普查 抽样调查,三、特点与类型 Characteristics and categories,Category CensusSampling survey,17,The census of the lifetime alcohol drinking status in America population,明确调查目的和类型确定研究对象确定样本量和抽样方法资料的收集资料的整理与分析常见偏倚及其控制研究的优点与局限性,第二节 现况研究的设计与实施 Design and implementation of cros
10、s-sectional study,To make the purpose and category of study To select the objects To determine the sample size and sampling method To collect data To sort and analyze data Bias and control Advantage and limitation,19,一、明确调查目的和类型 To make the purpose and category of study,根据研究提出的问题，明确调查目的 根据具体研究目的确定是普
11、查还是抽样调查,To make the purpose by the proposal of the studyTo select the survey method reference to the aim, census or sampling survey.,20,二、确定研究对象 To select the objects,某个区域内的全体居民或其中一部分 某一时点上的流动人员 某些特殊群体,Entire or part of the population in a region Floating population at a particular point of time. Ce
12、rtain special groups of people,三、确定样本量和抽样方法 To determine the sample size and sampling method,确定样本量预期现患率 ( P )允许误差（d）显著性水平（）,To determine the sample sizeExpected prevalence( P )Allowable error（d）Significance level（）,22,计量资料样本大小估计公式 Formulas for Numerical data,计数资料样本大小估计公式 Formulas for Categorical dat
13、a,23,抽样方法 Sampling Method非随机抽样Non-random sampling 随机抽样Random sampling,非随机抽样 Non-random sampling,选择样本时，加入人主观因素，使总体中每个个体被抽取的机会是不均等的,Non-random samples are selected by any kind of procedure that does not give all cases in the population equal chances to fall into the sample.,25,随机抽样 Random sampling,总体中
14、每一个对象都有同等机会被选入作为研究对象,Every person in the target population has the same known (and non-zero) chance of being included in the survey,26,随机抽样 Random sampling,单纯随机抽样 系统抽样 整群抽样分层抽样多级抽样,Simple random samplingSystematic samplingClustering samplingStratified samplingMultistage sampling,方 法,Methods,27,单纯随机抽
15、样(简单随机抽样),最简单、最基本的抽样方法 从总体N个对象中，利用抽签或其他随机方法抽取n个 总体中每个对象被抽到的概率相等,Simple random sampling,Simplest and basic method To select number n subjects by drawing lot or by using a table of random number from population with N units Equal chance for each subject in the target population,28,图31 总体与样本示意图,Fig 31
16、Diagram of population and sample,29,系统抽样(机械抽样),将总体各个个体单位按某种标志排列、连续编号 根据总体数N和确定的样本数n，计算抽样距离（N/n）,Systemic sampling,Rank every units by a character construct and number them Define the size of the sample and calculate sampling interval (k = N/n),30,系统抽样(机械抽样),3. 用单纯随机方法在第一组中确定一个起始号 4. 从此起始点开始，每隔K（K=N/
17、n）个单位抽取一个作为研究对象,Systemic sampling,3. Draw a random number ( k) for starting 4. Draw every k units from first unit,31,图32 系统抽样示意图,Fig 32 Diagram of systemic sampling,32,Example: Systematic sampling,33,整群抽样,Cluster sampling,The entire population of interest is divided into groups, or clusters, and a r
18、andom sample of these clusters is selected.,单纯整群抽样（Simple cluster sampling） 二阶段抽样（Two stages sampling）,将总体分成若干群组，抽取其中部分群组作为观察单位组成样本,34,图33 整群抽样示意图,Fig 33 Diagram of cluster sampling,Section 4,Section 5,Section 3,Section 2,Section 1,Example: Cluster sampling,36,分层抽样,Stratified sampling,First, stratif
19、y the population into several strata by character of areas, ages, etc. then select objects using random sampling in each strata.,将总体单位按某种特征分为若干次级（层），然后从每一层内单纯随机抽样组成一个样本。,37,分层抽样,Stratified sampling,按比例分配（proportional allocation）最优分配（optimum allocation),38,图34 分层抽样示意图,Fig 33 Diagram of cluster sampli
20、ng,39,Example: stratified sampling,40,多级抽样,将抽样过程分阶段进行，每个阶段使用的抽样方法往 往不同，即将以上抽样方法结合使用，在大型流行病 学调查中常用。,Multistage sampling,Multi-stage sampling is a kind of complex sample design in which two or more levels of units are imbedded one in the other.,41,一级抽样单位 Primary units,二级抽样单位 Secondary units,多级抽样 Multi
21、stage sampling,42,检查资料完整性和准确性 按标准归类、核实,五、资料的整理与分析,Data sort and analysis,Check the integrity and accuracy of data Classify and verify data by standard,43,44,Example:,46,Cork and Kerry Diabetes & Heart Disease Study, 1998,Prevalence of hypertension by age and sex,47,Example of Cross-Sectional Study,H
22、ypothesis:Obesity is a risk factor for knee osteoarthritis Sample:100 retirees living at “University Village”,48,Medical exam + X-rays to diagnose osteoarthritis of the knee,Osteoarthritis,+,-,40,10,20,30,+,-,Obesity,50,50,49,Prevalence of osteoarthritis among obese subjects:40/50 = 0.8 Prevalence o
23、f osteoarthritis among non-obese subjects: 20/50 = 0.4Prevalence ratio = 0.8/0.4 = 2.0,50,Obese subjects are two times more likely to have osteoarthritis of the knee than non-obese subjects.,51,Cross-Sectional Study,What came firstly? Obesity or Osteoarthritis？,Chicken or egg dilemma ?,常见的偏倚偏倚的控制,六、
24、偏倚及其控制,Common type of biasControl of bias,53,常见的偏倚 Common type of bias,选择偏倚 选择性偏倚 无应答偏倚 幸存者偏倚 信息偏倚 回忆偏倚 报告偏倚 测量偏倚,Selection Bias Selection bias Non-response bias Survivor bias Information Bias Recall bias Report bias Measurement bias,54,确保随机化原则 提高研究对象的依从性和受检率 正确选择测量工具和检测方法 培训调查员 做好资料的复查复核工作 辨析混杂因素,偏
25、倚的控制 Control of bias,Principle of randomization To improve the compliance of subjects and examination rate To apply proper measurement tools and test methods Training investigators Review data carefully Distinguish and analyze confounding factors,55,优 点 Advantage,常用抽样调查，结果有较强推广意义 有来自同一群体的自然形成的同期对照组，
26、结果具有可比性 可同时观察多种因素,三、研究的优点和局限性 Advantage and limitation,Common sampling survey with strong extension results With a control group from the same group over the same period formed naturally Can observe a variety of factors simultaneously,难以确定先因后果的时相关系 不能获得发病率资料 难以调查死亡病例、病程短、已痊愈的病例,局 限 性 Limitation,Do n
27、ot establish the true temporal sequence of events. Does not yield incidence or true relative risk. They are not feasible for the cases of death, recovery and short course.,57,第三节 研究实例 Example,研究背景 Background研究方法 Study Method 研究结果 Results,58,“反 应 停” 灾 难 Thalidomide Disaster,59,研究背景 Background,20世纪50年
28、代，科学家推出一种新药，据说它能在妊娠期控制精神紧张，防止孕妇恶心，并且有安眠作用。这药名叫“反应停”（沙利度胺、酞胺哌啶酮）。,Introduced in 1956 as sedative (sleeping pill) and to reduce nausea and vomiting during pregnancy，named Thalidomide,60,研究背景 Background,医生们对很多新生儿四肢缺如或畸形开始产生警觉，究其原因是孕妇服用了“反应停”。该药在1961年被禁用全世界约有8000名婴儿已经受害,Discovered to be a human teratoge
29、n causing absence of limbs or limb malformations in newbornsWithdrawn in 1961About 8000 infants effected,分子式,Molecular formula,反应停 Thalidomide,62,反应停引起的主要畸形的构成比 Ratio of deformities induced by Thalidomide,63,203个短肢畸形病例中合并其他畸形 203 cases of phocomelia associated with other malformations,64,* 反应停从国外购来
30、(Thalidomide purchased from other countries),反应停销售量与短肢畸形数的关系 Relationship between sales of Thalidomide and numbers of phocomelia,65,短肢畸形例数,反应停销售量（占销售总量的比例）,5,10,15,20,1958,1959,1960,1961,1962年,50,100,150,西德反应停销售总量（虚线）与短肢畸形例数（实线）的时间分布,Time distribution of Thalidomide sales (dotted line) and phocomeli
31、a numbers (solid line) in West Germany,66,Resulted in new drug testing rules！,概 念研究目的研究类型优点与局限 研究实例,第四节 生态学研究 Ecological Study,Definition Purpose Category Advantage and limitation A case study,68,描述性研究的一种群体的水平上研究某种因素与疾病的关系,A descriptive studyFocus on the relationship between exposure factors and dis
32、ease based on population,一、概念 Definition,69,以群体为观察和分析单位描述不同人群中某因素的暴露状况与疾病的频率，分析该暴露因素与疾病的关系,一、概念 Definition,Unit of observation and analysis is a population rather than an individual.Descript the frequency of exposure and disease to analyze the relationship between them in different population.,提供病因线
33、索，产生病因假设评估人群干预措施的效果,二、研究目的,Aims of study,To provide etiological clues and generate hypotheses for analytic studiesEvaluate the effect of interventions among population,71,生态比较研究生态趋势研究,三、研究类型,Ecological comparison studyEcological time trends study,Types of study,72,应用较多的一种方法 最简单的方法 观察不同人群或地区某种疾病的分布，根
34、据疾病分布的差异，提出病因假设,生态比较研究Ecological comparison study,A method applied frequently Simplest To observe the difference between the distributions of groups or regions, to generated the hypothesis according to the distribution.,73,To investigate the temporal relationship between the exposure and disease by
35、observing and comparing the fluctuations of average exposure level and frequency changes of disease in a population，finding the fluctuations trend.,连续观察不同人群中某因素平均暴露水平的改变和(或)某种疾病发病率、死亡率变化的关系，了解变动趋势，比较暴露水平变化前后疾病频率的变化情况，判断某因素与某疾病的联系,经济，出结果快 提供病因未明疾病的病因线索 对个体剂量无法测量的情况，是唯一可供选择的方法,优 点,四、优点与局限 Strengths an
36、d limitations,Quick, inexpensive, does not require time consuming data collection Can help in formulating hypothesis for the disease of unknown etiology The only way to the Circumstances of individual doses can not be measured,Strengths,适用于研究因素暴露变异范围小，较难测量暴露与疾病的关系 人群干预措施的评价及估计疾病发展趋势,优 点,四、优点与局限 Stre
37、ngths and limitations,Strengths,Applies to study the exposures with narrow range of variation, hard to measure the relationship between exposure and disease Applies to evaluate the effect of interventions in population and estimate the disease trends,出现生态学谬误 难以控制混杂因素 存在多重共线性问题 难以确定因果联系,局限性,Ecologica
38、l fallacyDifficult to control confoundingMulticollinearity problems Difficult to determine causal relationship,Limitations,250,200,150,100,50,0,0,1600,1400,1200,1000,800,600,Japan,Denmark,New Zealand,Fed. Repub. Of Germany,France,Canada,Israel,Switzerland,USA,Australia,Yugoslavia,Hong Kong,Romania,F
39、inland,Poland,Spain,Hungary,Norway,UK,Italy,Sweden,Incidence Ratio per 100,000 Women,Per Capita Supply of Fat Calories,Prentice RL, Kakar F, Hursting S, et al: Aspects of the rationale for the Womens Health Trial. J Natl Cancer Inst 80:802-814, 1988.),Correlation between dietary fat intake and breas
40、t cancer by country 饮食脂肪摄入与乳腺癌发病,78,Is there a relationship between breast cancer incidence and dietary fat consumption by country?,From the graph, we see that as average dietary fat consumption increases, breast cancer incidence increases. What is wrong with this data? The problem is: the ecologic fallacy!,Prentice et al. J Natl Cancer Institute 1988 80:802-814,
