哈尔滨医科大-描述性研究课件

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 University1Methods of studyObservational ExperimentalTheoreticalDescriptive studyAnalytic studyClinical trialField trialCommunity interventionthree types of basic methodsCase-control studyCohort studyCross-sectional stu

2、dyEcological study2Epidemiology is the study of the distribution and determinants of disease frequency in human population.Epidemiology: Principles and Methodsby Brian MacMahon 19963?The distribution of Disease considers Who is getting disease? Where is disease occurring? When is disease occurring?4

3、PersonPlaceTimeCasesDescriptive Epidemiology Who? Where? When? 5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 studyDesign and implementation of cross-sectional studyA case studyEcological studyOutline7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 concept Mecha

4、nism Purposes and applications Characteristics and categories 8TimeDZDZEE-10TimeSchematic diagram of Cross-sectional StudyT1T2T311 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 disease or health events within populations To provide etiologica

5、l clues12 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 population To evaluate the effect of surveillance，vaccination and disease prevention and control14 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 c

6、ategories CharacteristicsNo control group Particular point of timeLimit to ensure the causal relationshipTo prompt causal relationship for the exposures that wont be changed15The census of the lifetime alcohol drinking status in America population17 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

7、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 cross-sectional studyTo make the purpose and category of studyTo select the objectsTo determine the sample size and sampling methodTo collect data To sort and analyze dataBias and controlAdvantage and limitation一、明确调查目的和类型To make the purpose and

8、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查还是抽样调查 To make the purpose by the proposal of the study To select the survey method reference to the aim, census or sampling survey.19二、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 regionFloating popula

9、tion at a particular point of time. Certain special groups of people20三、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 size Expected prevalence( P ) Allowable error（d） Significance level（）计量资料样本大小估计公式Formulas for Numerical data计数资

10、料样本大小估计公式Formulas for Categorical data 22 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. 随机抽样 Random sampling总体中每一个对象都有同等机会被选入作为研究对象Every person

11、in the target population has the same known (and non-zero) chance of being included in the survey25单纯随机抽样(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 samplingSimplest and basic methodTo select number n subjects by drawing lot or by using a table of random number from pop

12、ulation with N units Equal chance for each subject in the target population 27图31 总体与样本示意图Fig 31 Diagram of population and sample28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 samplingRank every units by a character construct and number themDefine the size of the sample and cal

13、culate sampling interval (k = N/n)29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/n）个单位抽取一个作为研究对象 Systemic sampling3. Draw a random number ( k) for starting 4. Draw every k units from first unit30图32 系统抽样示意图Fig 32 Diagram of systemic sampling31Example: Systematic sampling32整群抽样Cluster samplingT

14、he entire population of interest is divided into groups, or clusters, and a random 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33图33 整群抽样示意图Fig 33 Diagram of cluster sampling34Section 4Section 5Section 3Section 2Section 1

15、Example: Cluster sampling35分层抽样Stratified samplingFirst, stratify 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。36分层抽样Stratified sampling 按比例分配（proportional allocation） 最优分配（optim

16、um allocation)37图34 分层抽样示意图Fig 33 Diagram of cluster sampling38Example: stratified sampling39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 samplingMulti-stage sampling is a kind of complex sample design in which two or more levels of units are imbedded one in the other. 40一级抽样

17、单位Primary units 二级抽样单位Secondary units多级抽样 Multistage sampling41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 standard42Target Population or Sampling FrameCensus or Sampling SurveySampleDiseaseAndExposureNon-diseaseandExposu

18、reNon-diseaseandNon-exposureDiseaseandNon-exposure4344Example:Job A (hazardous)100 Workers80 Healthy20 Respiratory symptoms80 well10 wellJob B (hazardous)100 Workers95 Healthy5 Respiratory symptoms95 well15 wellPoint YPoint XPrevalence rate of respiratory symptoms in Job A20%(20/100)11%(10/90)Preval

19、ence rate of respiratory symptoms in Job B5%(5/100)14%(15/110)Ratio of prevalence rates, Job A/Job B:4.00.8Cork and Kerry Diabetes & Heart Disease Study, 1998Prevalence of hypertension by age and sex46Example of Cross-Sectional StudyHypothesis:Obesity is a risk factor for knee osteoarthritisSample:

20、100 retirees living at “University Village”47Medical exam + X-rays to diagnose osteoarthritis of the kneeOsteoarthritis+-40102030+-Obesity505048Prevalence of osteoarthritis among obese subjects: 40/50 = 0.8Prevalence of osteoarthritis among non-obese subjects: 20/50 = 0.4Prevalence ratio = 0.8/0.4 =

21、 2.049Obese subjects are two times more likely to have osteoarthritis of the knee than non-obese subjects.50Cross-Sectional StudyWhat came firstly?Obesity or Osteoarthritis？Chicken or egg dilemma ?51 常见的偏倚 偏倚的控制六、偏倚及其控制 Common type of bias Control of bias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

22、息偏倚回忆偏倚报告偏倚测量偏倚Selection BiasSelection biasNon-response bias Survivor biasInformation BiasRecall biasReport biasMeasurement bias53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倚的控制 Control of biasPrinciple of randomizationTo improve the compliance of subjects and examination rateTo apply

23、proper measurement tools and test methodsTraining investigatorsReview data carefullyDistinguish and analyze confounding factors 54 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，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 limitationCommon sampling survey with strong extension results With a control g

24、roup from the same group over the same period formed naturallyCan observe a variety of factors simultaneously55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 LimitationDo not establish the true temporal sequence of events.Does not yield incidence or true relative risk.They are not feasible for the

25、cases of death, recovery and short course.第三节 研究实例 Example 研究背景 Background 研究方法 Study Method 研究结果 Results57 “反 应 停” 灾 难Thalidomide Disaster58研究背景Background20世纪50年代，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 vo

26、miting during pregnancy，named Thalidomide59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 teratogen causing absence of limbs or limb malformations in newborns Withdrawn in 1961 About 8000 infants effected60分子式Molecular formula 反应停 Thalido

27、mide61主要畸形个人观察信访例数%例数%手臂4352.410350.7手臂与腿2328.16029.6手臂、腿、耳22.473.4手臂与耳33.7104.9耳78.5146.9腿11.242.0其他畸形33.752.5合 计42203反应停引起的主要畸形的构成比Ratio of deformities induced by Thalidomide62合并畸形例数合并畸形例数幽门2无脑2十二指肠狭窄3心脏17十二指肠闭锁3小脑3食道闭锁2眼1肛门闭锁17鼻1203个短肢畸形病例中合并其他畸形203 cases of phocomelia associated with other malfo

28、rmations63国家反应停销售量（公斤）短肢畸形病例数奥地利2078比利时25826英国5769349荷兰14025挪威6011葡萄牙372瑞士1136西德300995000美国2510+7* 反应停从国外购来 (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 phocomelia64短肢畸形例数反应停销售量（占销售总量的比例）510152019581959196019611962年 50100150西德反应停

29、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 phocomelia numbers (solid line) in West Germany65 “反应停儿童”的事件是一次惨痛的教训。它提醒人们，任何新药在用于临床之前必须经过彻底检验。Resulted in new drug testing rules！66 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 StudyDefinitionPurposeCategoryAdvantage an

30、d limitationA case study 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 study Focus on the relationship between exposure factors and disease based on population一、概念 Definition68 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

31、 individual. Descript the frequency of exposure and disease to analyze the relationship between them in different population. 69 提供病因线索，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 studies Evaluate the effect of interventions among populati

32、on 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 study71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 frequentlySimplestTo observe the difference between the distributions of groups or regions, to generated

33、the hypothesis according to the distribution.72 生态趋势研究 Ecological trend studyTo investigate the temporal relationship between the exposure and disease by observing and comparing the fluctuations of average exposure level and frequency changes of disease in a population，finding the fluctuations trend

34、.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73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 and limitationsQuick, 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Strengths and limitations Strengths Applies to study the exposures with narrow range of va