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1.
空间流行病学中的偏倚与混杂   总被引:1,自引:1,他引:1  
目的探讨空间流行病学中的偏倚与混杂。方法结合实例分析空间流行病学中可能存在偏倚与混杂及其对研究结果的可能影响。结果空间流行病学研究中存在选择性偏倚,确证、分子和分母偏倚,由疾病诱导期/潜隐期的选择和暴露-疾病模式的错误载明所致的偏倚,暴露不准确偏倚,空间相关性,显著性检验,生态学偏倚和社会-经济混杂等8种偏倚与混杂。结论空间流行病学研究中的偏倚来源众多且较为复杂,由此可以夸大或掩盖研究结果,故对研究结果的解释应慎重。  相似文献   

2.
医院感染危险因素研究中的混杂偏倚   总被引:3,自引:1,他引:2  
在医院感染危险因素的研究中,有些研究者往往忽视了混杂偏倚的存在,本文选出两篇有关论文就其混杂偏倚问题进行分析,并列出了控制混杂偏倚的几种主要方法,提醒研究者注意预防和控制混杂偏倚  相似文献   

3.
对偏倚与混杂的认识和定义虽然在不断深入和改变,但流行病学家们从未忽略控制偏倚和混杂的重要性。历史上,对于偏倚的定义已经包含三个主要意思:①观察者的偏见;②器械错误造成的偏差;③错误的研究设计造成的结果。20世纪70年代出现的偏倚类型学对于定义在流行病学研究设计、实施和分析过程中存在的偏离真实值的情况有很大的帮助。随后,偏倚逐渐形成了更加正式和系统的定义。现代流行病学把偏倚归纳为选择偏倚、信息偏倚和混杂偏倚。混杂可以看作是偏倚的一个特殊类型,在简明牛津英文词典中提到它是一个中世纪的拉丁文词:“con-fundere”,意思是混在一起,源自中世纪法语“confondre”。  相似文献   

4.
在流行病学研究中,选择偏倚会导致研究样本无法代表一般人群,使研究结果偏离真实值,无法推断真实的因果关联。本文通过构建有向无环图(directed acyclic graphs,DAGs),将复杂的因果关系可视化,提供识别选择偏倚的直观方法,并通过冲撞分层偏倚的图形结构来验证不同类型的选择偏倚。在实际研究中,可能同时存在多种偏倚,对冲撞变量进行不恰当的调整会新增冲撞分层偏倚,打开后门路径,引入混杂偏倚,甚至改变原有混杂偏倚的大小与方向。为了得到暴露到结局的无偏估计,研究者可以通过构建DAGs,帮助识别冲撞变量,防止冲撞偏倚的发生。  相似文献   

5.
检出偏倚是一种常见的信息偏倚,在Horwitz绝经后服用雌激素与子宫内膜癌之间的关联研究中首次被提出,并广泛地存在于各类流行病学研究中。本文应用有向无环图,分析暴露-结局间的效应,并以测量的暴露-测量的结局间的关联来估计;检出偏倚的产生,实质上是从测量的暴露至测量的结局之间存在着的额外的、与研究兴趣无关的开放路径所致。通过对不同研究设计如队列研究、随机对照临床试验和病例对照研究等进行具体分析,了解检出偏倚的产生机制及其对效应估计(或关联)的可能影响。  相似文献   

6.
无应答偏倚     
无应答偏倚是流行病学调查中一种常见的偏倚,它可以导致调查结果或估计值的真实性和可靠性下降。因此,国外学者较重视这方面的研究。本文就近年来的有关无应答偏倚的研究进展作一综述,旨在使医学科研工作者重视无应答偏倚的预防与控制,以提高调查研究的质量。  相似文献   

7.
生态偏倚有时归因于组变量(生态分析单位)的混杂,或与组变量有关的危险因素.不管组变量或效应修饰因子是否独立的危险因素,效应修饰可导致很大的生态偏倚.此外,引起生态偏倚的其他危险因素,其本身不一定在个体水平上与研究变量有关.这样,因协同变量导致生态偏倚的条件比因其导致个体水平的混杂的条件要广泛得多.与生态偏倚有关的变量的标化或生态控制,一般不能充分地消除这种偏倚.  相似文献   

8.
左群  何蓓  胡高潮  张宗光  刘辉 《现代预防医学》2011,38(23):4884-4885
本文分析了当前流行病学研究中偏倚问题的存在现状,从完善新型城市医疗卫生服务协作体系的角度,论述了在新的医疗卫生服务模式下,服务对象个人健康信息的完善对流行病学人群研究中控制失访偏倚、无应答偏倚、回忆偏倚、说谎偏倚、现患病例-新病例偏倚和混杂偏倚等的助益作用.  相似文献   

9.
偏倚风险评估系列:(七)预后因素研究   总被引:2,自引:2,他引:0       下载免费PDF全文
本讲座主要介绍采用QUIPS(Quality In Prognosis Studies)工具对预后因素研究中出现的偏倚进行评估,介绍相关评估要点,举例说明QUIPS工具的使用,并对该工具在使用中值得商榷的地方进行了讨论。该工具主要涉及研究对象、研究失访、预后因素测量、结局测量、研究混杂以及统计分析和报告6个方面,为预后因素研究中的偏倚评价提供了一个全新的方法。  相似文献   

10.
无应答偏倚   总被引:1,自引:0,他引:1  
无应答偏倚是流行病学调查中一种常见的偏倚,它可以导致调查结果或估计值的真实性和可靠性下降。因此,国外学者较重视这方面的研究。本文就近年来的有关无应答偏倚的研 究进展作一综述,旨在使医学科研工作者重视无应答偏倚的预防与控制,以提高调查研究的质量。  相似文献   

11.
Biases associated with volunteering for studies in human sexuality were studied. Beginning with a sample of over 1000 introductory psychology students, subjects participated in a two-phase study in which those willing and unwilling to volunteer for a variety of sexuality studies were compared. In both phases of this study, volunteers were significantly different from nonvolunteers on some, but not all, dimensions assessed. Specifically, compared to nonvolunteers, volunteers reported a more positive attitude towards sexuality, less sexual guilt, and more sexual experience. These differences were independent of subject gender. Sobering implications of these findings for the generalizability of sexuality research results are discussed.  相似文献   

12.
13.
Efron's biased coin design is a restricted randomization procedure that has very favorable balancing properties, yet it is fully randomized, in that subjects are always randomized to one of two treatments with a probability less than 1. The parameter of interest is the bias p of the coin, which can range from 0.5 to 1. In this note, we propose a compound optimization strategy that selects p based on a subjected weighting of the relative importance of the two fundamental criteria of interest for restricted randomization mechanisms, namely balance between the treatment assignments and allocation randomness. We use exact and asymptotic distributional properties of Efron's coin to find the optimal p under compound criteria involving imbalance variability, expected imbalance, selection bias, and accidental bias, for both small/moderate trials and large samples. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

14.
目的通过比较两种统计结果产生的统计学差异,分析目前学生视力低下评价方法存在的选择性偏倚。方法收集某校学生体检视力检查结果,共调查3 003人,分别以视力低下人数和视力低下眼数为统计样本,进行分析。结果调查3 003人(6 006眼),视力低下率为63.24%(57.49%),差异有统计学意义(χ2=27.393,P0.01);不同学习阶段学生视力低下率不同,小学生、初中生和高中生视力低下率分别为51.07%、74.88%和93.38%,差异有统计学意义(χ2人数=315.335,P0.01);男女生视力低下率差异无统计学意义。高中生重度视力低下比例较高,与小学生和初中生比较差异有统计学意义(χ2人数人数=567.874,P0.01;χ2眼数=912.474,P0.01)。结论以视力低下人数评价视力低下状况会高估视力低下检出率;双眼视力不一致时以较差眼视力为准的评价方法可能导致统计结果出现偏差。  相似文献   

15.
OBJECTIVE: To examine the relationship between eating disorders and attentional biases. METHOD: The first study comprised 23 female patients with clinical eating disorders, women with high levels of anxiety (n = 19), and three female normal control groups comprising low (n = 31), moderate (n = 21), or high levels of shape concern (n = 23). The second study comprised 82 women with clinical eating disorders and 44 healthy controls. All participants completed measures of eating disorder psychopathology and completed a modified pictorial dot-probe task. RESULTS: In the first study, biases were found for negative eating and neutral weight pictures, and for positive eating pictures in women with eating disorders; these biases were greater than those found in anxious and normal controls. The second study replicated these findings and biases were also found for negative and neutral shape stimuli. CONCLUSION: It is concluded that future research should establish whether such biases warrant specific therapeutic interventions.  相似文献   

16.
Self‐selection in epidemiological studies may introduce selection bias and influence the validity of study results. To evaluate potential bias due to self‐selection in a large prospective pregnancy cohort in Norway, the authors studied differences in prevalence estimates and association measures between study participants and all women giving birth in Norway. Women who agreed to participate in the Norwegian Mother and Child Cohort Study (43.5% of invited; n = 73 579) were compared with all women giving birth in Norway (n = 398 849) using data from the population‐based Medical Birth Registry of Norway in 2000–2006. Bias in the prevalence of 23 exposure and outcome variables was measured as the ratio of relative frequencies, whereas bias in exposure‐outcome associations of eight relationships was measured as the ratio of odds ratios. Statistically significant relative differences in prevalence estimates between the cohort participants and the total population were found for all variables, except for maternal epilepsy, chronic hypertension and pre‐eclampsia. There was a strong under‐representation of the youngest women (<25 years), those living alone, mothers with more than two previous births and with previous stillbirths (relative deviation 30–45%). In addition, smokers, women with stillbirths and neonatal death were markedly under‐represented in the cohort (relative deviation 22–43%), while multivitamin and folic acid supplement users were over‐represented (relative deviation 31–43%). Despite this, no statistically relative differences in association measures were found between participants and the total population regarding the eight exposure‐outcome associations. Using data from the Medical Birth Registry of Norway, this study suggests that prevalence estimates of exposures and outcomes, but not estimates of exposure‐outcome associations are biased due to self‐selection in the Norwegian Mother and Child Cohort Study.  相似文献   

17.
Instrumental variable (IV) analysis can be used to address bias due to unobserved confounding when estimating the causal effect of a treatment on an outcome of interest. However, if a proposed IV is correlated with unmeasured confounders and/or weakly correlated with the treatment, the standard IV estimator may be more biased than an ordinary least squares (OLS) estimator. Several methods have been proposed that compare the bias of the IV and OLS estimators relying on the belief that measured covariates can be used as proxies for the unmeasured confounder. Despite these developments, there is lack of discussion about approaches that can be used to formally test whether the IV estimator may be less biased than the OLS estimator. Thus, we have developed a testing framework to compare the bias and a criterion to select informative measured covariates for bias comparison and regression adjustment. We also have developed a bias-correction method, which allows one to use an invalid IV to correct the bias of the OLS or IV estimator. Numerical studies demonstrate that the proposed methods perform well with realistic sample sizes.  相似文献   

18.
In drug development, clinical medicine, or health policy making, basing one’s decisions on a selective part of the available evidence can pose a major threat to the health of patients and the society. If, for example, primarily positive research reports are taken into account, one could wrongfully conclude that a harmful drug is safe. The systematic error introduced by summarizing evidence that is not representative of the available evidence is commonly referred to as “publication bias.” Some, however, prefer other terms to refer to the same concept. In this article, we explore the terminology and concepts relevant to this bias and propose a more systematic nomenclature than what is currently used.  相似文献   

19.
ObjectiveThe objective of the present study was to determine the publication rate of cancer randomized controlled trial (RCTs) and to analyze the determinants of the publication, as well as to estimate the possible existence of a location and time lag bias. We also described the bibliometric characteristics of the publications.Study design and SettingWe conducted an observational study that identified publications resulting from RCTs involving cancer-related drug products. These studies were authorized and registered by the Spanish Agency of Medicines and Medical Devices between 1999 and 2003.ResultsWe identified 168 publications of 303 RCTs, resulting in a publication rate of 55.4% after a mean follow-up of 12 years. The only factor associated to the likelihood of nonpublication was the study setting favoring only national RCTs (odds ratio 2.7; 95% confidence interval 1.5–4.8). Type of sponsor did not seem to be associated, although the largest volume of nonpublished trials is international, industry-sponsored. Positive results seemed to be associated to a publication in a higher impact factor journal and a shorter time-to-publication.ConclusionsAbout half of the cancer RCTs during the target period have not been published. The national setting is a factor associated to nonpublication, whereas the direction of results determines its dissemination (impact factor and timely publication).  相似文献   

20.
中国2009年公布的艾滋病疫情估计报告显示~([1]),现存活的74万HIV/AIDS中,经异性性接触传播占43%,经同性传播占16%.说明性传播已经成为我国HIV的主要传播途径.通过调查得到各类人群中性行为情况的资料可以用于了解感染HIV高危行为的发生情况、HIV的传播途径、高危行为发生的原因,确定干预的目标人群和评价干预效果.  相似文献   

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