Patterns of non-response to a mail survey

This paper describes a basic investigation of possible non-response bias in a mail survey. We compare characteristics of responders and non-responders to a mail survey of health outcomes among participants of a longitudinal study of physical activity, physical fitness, and health. Results indicate that, at the first clinic visit, the responders were essentially the same as the non-responders on personal health history and laboratory measurements, while reporting significantly more family history of specific chronic diseases (cardiovascular disease, hypertension, stroke). The male responders were younger and reported more positive health behaviors as well as better weight and treadmill times at the first clinic visit. These results suggest that both response groups were equally healthy at entry, and that individuals who had family members with certain chronic conditions and who had positive health behaviors were more likely to respond (participate) in this health-related survey. Differences of this type could affect interpretation of future analyses. This work illustrates the importance of incorporating methods to examine non-response into any epidemiologic study.     

老年高血压患者社区随访及血压控制情况

目的评价社区经常就诊的老年高血压患者血压控制及随访情况。方法通过社区高血压患者管理软件,收集患者就诊基线及1年内随诊资料。结果共收集60岁以上高血压患者3375例。基线血压控制率为63．5％,66．9％随访6个月以上。基线血压、第3、6个月血压控制率分别为61．8％,62,4％和61．6％,血压控制率没有统计学意义（x^2=0．16,P=0．69）。基线血压控制良好者3、6个月随访血压控制率分别为72．9％和72．1％,血压控制率没有统计学意义（x^2=0,26,P=0．61）。基线、3、6个月血压均控制的高血压患者与血压控制不良者相比,服药比例分别为96．2％和97．7％,没有明显统计学意义（x^2=3．58,P=0．06）;体育锻炼、限盐、控制体重对提高控制率有显著影响。结论经常到社区就诊的高血压患者血压控制率较高,糖尿病、收缩压控制不良是影响血压控制率的重要因素。体育锻炼、限盐、控制体重有助于提高血压控制率。血压控制良好者可3—6个月随访1次。     

Prior health care utilization as a potential determinant of enrollment in a 21-year prospective study, the Millennium Cohort Study

Results obtained from self-reported health data may be biased if those being surveyed respond differently based on health status. This study was conducted to investigate if health, as measured by health care use preceding invitation, influenced response to invitation to a 21-year prospective study, the Millennium Cohort Study. Inpatient and outpatient diagnoses were identified among more than 68,000 people during a one-year period prior to invitation to enroll. Multivariable logistic regression defined how diagnoses were associated with response. Days spent hospitalized or in outpatient care were also compared between responders and nonresponders. Adjusted odds of response to the questionnaire were similar over a diverse range of inpatient and outpatient diagnostic categories during the year prior to enrollment. The number of days hospitalized or accessing outpatient care was very similar between responders and nonresponders. Study findings demonstrate that, although there are some small differences between responders and nonresponders, prior health care use did not affect response to the Millennium Cohort Study, and it is unlikely that future study findings will be biased by differential response due to health status prior to enrollment invitation. In addition to the authors, the Millennium Cohort Study Team includes Edward J. Boyko, MD, MPH (Seattle Epidemiologic Research and Information Center, Department of Veterans Affairs Puget Sound Health Care System, Seattle, WA); Gary D. Gackstetter, PhD, DVM, MPH and Tomoko I Hooper, MD MPH (Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, Bethesda, MD); Gary D. Gackstetter, PhD, DVM, MPH (Analytic Services, Inc. (ANSER), Arlington, VA); Gregory C. Gray, MD, MPH (College of Public Health, University of Iowa, Iowa City, IA); and James R. Riddle, DVM, MPH (Air Force Research Laboratory, Wright-Patterson Air Force Base, OH). This represents report 07-07, supported by the Department of Defense, under work unit no. 60002. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of the Army, Department of the Air Force, Department of Defense, Department of Veterans Affairs, or the US Government. This research has been conducted in compliance with all applicable federal regulations governing the protection of human subjects in research (Protocol NHRC.2000.007).     

队列研究中的依时混杂偏倚和随访时间偏倚

【导读】未加识别或控制的混杂因素和偏倚会影响流行病学研究中因果关系的准确判断。目前已熟知队列研究中可能出现的选择偏倚及失访偏倚,为此笔者复习了队列研究中可能存在的依时混杂偏倚及其控制方法,并通过实例提出随访时间偏倚的概念及其控制方法。     

Cohort studies: History of the method I. prospective cohort studies

The term "cohort study" was introduced by Frost in 1935 to describe a study that compared the disease experience of people born at different periods, in particular the sex and age specific incidence of tuberculosis and the method was extended to the study of non-communicable disease by Korteweg who used it 20 years later to analyse the epidemic of lung cancer in the Netherlands. Such studies are now best described as generation studies or generation cohort studies to distinguish them from the common type of study that is now carried out that consists in defining groups of individuals distinguished by some variable (such as place of residence, occupation, behaviour, or environmental exposure) and following them up to see if the incidence or mortality rates vary with the selected variable. This type of study is now one of the most important tools for epidemiological investigation. Initially called prospective studies, because the information characterising the individuals in the cohorts was recorded before the onset of disease, they are now preferably called cohort studies and distinguished as prospective cohort studies, If the information obtained relates to the subjects at the time the study is started and they are then followed, or retrospective cohort studies, if the information characterising the individuals was recorded sometime in the past (for example, the receipt of radiotherapy, or entry to a specific occupation). Studies of either type have the great advantage that they avoid all the most important sources of bias that may affect case-control-studies, but the disadvantage that because incidence rates and more specifically mortality rates are commonly low, large numbers of subjects have to be followed for several (if not many) years to obtain statistically significant results. Several early prospective studies are described: Namely, those of 34,000 male British doctors, 190,000 male and female American citizens with different smoking habits, some 5,000 middle aged residents of Framingham with different blood pressures, blood cholesterol levels, etc, and 13,000 children born in the UK in one week in 1946 with different family backgrounds.     

肝移植随访管理中健康信念模式的建立及前瞻随机对照的临床研究

目的建立肝移植特异性健康信念模式并探讨其对受者生存状况的影响。方法对在我院长期随诊的肝移植受者采取问卷调查的方式获得该群体最关切的健康问题和期望的随访模式，建立肝移植特异性健康信念模式，采取前瞻、随机、对照的研究方式用该模式干预肝移植健康管理和随访过程，观察该信念模式对肝移植受者生存状况的影响。结果（1）共有374人接受问卷调查，肝移植受者所关注的问题集中在随访的意义及合理用药等7个方面，希望通过成立移植之家和强化随访人员角色功能等方式参与随访并进行互动。（2）根据上述调查结果建立肝移植特异性健康信念模式，用该模式对前述接受调查的374例肝移植患者的健康管理和随访过程进行前瞻、随机、对照的干预研究，随诊2年，结果干预组（190例）肝功能异常、感染、原发病复发的发生率分别为16．8％（32／190）、3．2％（6／190）、2．6％（5／190）；对照组（184例）分别为21．2％（39／184）、10．3％（19／184）、9．8％（18／184），差异有统计学意义（P〈0．05）。结论建立肝移植特异性健康信念模式并用于肝移植术后健康管理和随访过程，可明显降低受者不良健康事件的发生率。     

A Bayesian approach to prospective binary outcome studies with misclassification in a binary risk factor

Misclassification in a binary exposure variable within an unmatched prospective study may lead to a biased estimate of the disease-exposure relationship. It usually gives falsely small credible intervals because uncertainty in the recorded exposure is not taken into account. When there are several other perfectly measured covariates, interrelationships may introduce further potential for bias. Bayesian methods are proposed for analysing binary outcome studies in which an exposure variable is sometimes misclassified, but its correct values have been validated for a random subsample of the subjects. This Bayesian approach can model relationships between explanatory variables and between exploratory variables and the probabilities of misclassification. Three logistic regressions are used to relate disease to true exposure, misclassified exposure to true exposure and true exposure to other covariates. Credible intervals may be used to make decisions about whether certain parameters are unnecessary and hence whether the model can be reduced in complexity.In the disease-exposure model, for parameters representing coefficients related to perfectly measured covariates, the precision of posterior estimates is only slightly lower than would be found from data with no misclassification. For the risk factor which has misclassification, the estimates of model coefficients obtained are much less biased than those with misclassification ignored.     

Predictors of locating children participants in epidemiological studies 20 years after last contact: internet resources and longitudinal research

This study examines predictors of locating participants that were last contacted 20 years ago using public web-search directories, in order to facilitate longitudinal environmental health research. Participants (n = 3,202) resided in four distinct geographical neighborhoods in Hamilton, Ontario during childhood; they were between 15 and 17 years old when they were last contacted in 1986. Data used for tracing included available addresses, telephone numbers, given names, and parental names. Reverse and forward search strategies were used to retrieve updated contact details. 43% of the sample was traced using online directories. Following ethical approval, participants were contacted using traced data and 29% of the original cohort was located. Predictors of locating participants were: availability of paternal names, being traced to original addresses or telephone numbers, gender (male), relatively higher socioeconomic status in childhood, and not being exposed to smoking in childhood. Where participants resided in childhood was not a significant predictor of locating participants. Although 13% of the sample was traced using forward search by name, only 4% were located. For participants traced to available addresses or telephone numbers, the difference between the proportions of traced and located participants was <3%. Prospective studies on children may benefit from including the listed names that pertain to each child’s telephone number and full parental names at recruitment, thereby increasing the likelihood of locating participants using Internet resources. Integrating the use of Internet-based public directories for cohort reconstruction can reduce financial costs related to follow-up for longitudinal research.     

农村HIV感染者艾滋病相关知识与安全套认知的随访研究

目的了解农村地区已婚的HIV感染者艾滋病相关知识与安全套认知情况，为进一步获得促进和提高HIv感染者家庭使用安全套的操作可行的综合干预方案提供依据和基础。方法对临泉县HIV感染者采用入户方式进行艾滋病知识宣传和安全套使用技巧培训。在随访前后，对研究对象采用统一问卷进行两次调查。结果研究对象在艾滋病传播途径、非传播途径和预防方法知识方面在随访后有提高。性交时主动提出使用安全套的女性由干预前的33．9％提高到38．7％。结论要进一步加大艾滋病宣传和防治，提高安全套使用率，重点加强女性与性伴商讨安全套使用的能力，克服免费索取安全套时的羞辱感。     

Incentives increased return rates but did not influence partial nonresponse or treatment outcome in a randomized trial

OBJECTIVE: Our aim was to analyze monetary incentives and shortening the questionnaire as means of increasing response rates in a mailed follow-up survey 1 year after inpatient psychotherapeutic treatment. Additionally, effects on partial nonresponse and the assessment of treatment outcome were examined. STUDY DESIGN AND SETTING: In a 2x2 factorial design, a sample of 3,825 patients was randomized to the two following interventions: (1) receiving a prepaid monetary incentive or none; and (2) getting a short or a long questionnaire. Treatment outcome was measured prospectively by a self-assessment instrument for psychopathology. RESULTS: When using incentives, the response rate significantly increased by 7.3% (95% confidence interval [CI] 2.6-11.9%). Receiving a short questionnaire led to an augmentation of the response rate of 3.7% (95% CI 0.9-8.3%), which was not significant. The corresponding odds ratios were significantly increased for monetary incentives (1.36; 95% CI 1.30-1.88), and when abridging the questionnaire (1.15; 95% CI 1.01-1.31). However, partial nonresponse and treatment outcome were independent of the two factors. CONCLUSION: Incentives and a shorter questionnaire led to higher return rates but did not affect partial nonresponse and self-report of treatment outcome in a randomized postal survey.     

重庆市男男性行为者HIV抗体阳转率及其影响因素研究

目的了解男男性行为者(men who have sex with men,MSM)人群HIV抗体阳转率及其影响因素,为评估MSM人群艾滋病防治效果与开展针对性防治工作提供依据。方法对招募自愿参加随访研究的HIV与梅毒均阴性的MSM进行随访,6个月后再次进行问卷调查与采集血样检测HIV与梅毒,以HIV抗体阳转率为应变量,人口学特征、性行为情况等为自变量进行Logistic回归,分析鉴别HIV抗体阳转率的影响因素。结果 214例MSM参加随访,平均年龄(25.6±6.3)岁,88.3%的人最近6个月与男性有肛交史,最近6个月平均性伴数为2个,最近一次与男性发生肛交时安全套使用率为76.2%,最近6个月发生保护性肛交的比例为52.4%。HIV抗体阳转率及95%CI为12.5(9.1～15.7)/100人年,梅毒的发病率及95%CI为17.8(13.1～23.5)/100人年。多因素回归分析显示,文化程度(OR=0.27,95%CI:0.13～0.59)、梅毒感染(OR=9.23,95%CI:2.42～35.18)是HIV抗体阳转率的独立影响因素。结论重庆市MSM人群HIV抗体阳转率高,安全套使用率低,防治形势严峻。     

队列研究随访之我见

队列研究提供的病因证据在各种观察性研究设计中具有最高的质量,最重要的原因之一是其先"因"后"果"的设计原理。因此,随访是队列研究的核心要素之一,有效的随访方法是队列研究质量的重要保障。本文简要介绍了队列研究中关于随访期的考虑,随访队列的两种主要方法及其各自的优缺点。     

Bayesian sensitivity analysis for unmeasured confounding in observational studies

We consider Bayesian sensitivity analysis for unmeasured confounding in observational studies where the association between a binary exposure, binary response, measured confounders and a single binary unmeasured confounder can be formulated using logistic regression models. A model for unmeasured confounding is presented along with a family of prior distributions that model beliefs about a possible unknown unmeasured confounder. Simulation from the posterior distribution is accomplished using Markov chain Monte Carlo. Because the model for unmeasured confounding is not identifiable, standard large-sample theory for Bayesian analysis is not applicable. Consequently, the impact of different choices of prior distributions on the coverage probability of credible intervals is unknown. Using simulations, we investigate the coverage probability when averaged with respect to various distributions over the parameter space. The results indicate that credible intervals will have approximately nominal coverage probability, on average, when the prior distribution used for sensitivity analysis approximates the sampling distribution of model parameters in a hypothetical sequence of observational studies. We motivate the method in a study of the effectiveness of beta blocker therapy for treatment of heart failure.     

首次脑卒中患者生存率和死亡影响因素的研究

目的 描述首次脑卒中患者生存情况, 分析影响其死亡的相关因素。方法 收集2009 年浙江省慢性病监测信息管理系统中首次脑卒中患者, 通过主动和被动随访获得患者生存状况及死亡原因。应用Kaplan-Meier 法进行生存率分析, 采用Cox比例风险回归模型对影响患者死亡的危险因素进行单因素和多因素分析。结果 共收集患者78 189 例, 脑梗死、大脑内出血、蛛网膜下腔出血和未特指分别占61.65%、30.42%、2.32%和5.62%。随访期间, 共33 265 例患者死亡, 其中根本死因与脑卒中相关的有27 147 例（81.61%）。患者当天即因脑卒中死亡6 122 例, 病死率为7.83%;第28 天病死率为21.01%;1～4 年生存率分别为72.04%、68.92%、66.27%和64.29%;脑梗死、大脑内出血、蛛网膜下腔出血和未特指的4 年生存率分别为80.06%、50.15%、71.80%和21.41%。模型主效应显示影响患者死亡的主要因素有年龄、性别、文化程度、诊治医院级别、高血压和脑卒中类型。年龄与性别存在交互作用（P＜0.001）, 单独效应显示男性在75 岁之前的死亡风险高于女性, 而75 岁之后则相反。结论 急性和亚急性期脑卒中死亡风险最高, 年龄、性别、文化程度、诊治医院级别、高血压和脑卒中类型是影响其预后的危险因素。     

中学生抑郁症状与父母受教育程度关系随访分析

目的了解中学生抑郁症状变化趋势和父母受教育水平的关系,为制定中学生抑郁症状的干预措施提供依据。方法采取整群抽样方法,于2009年及2010年采用抑郁自评量表(SDS)对南京市5所学校53个班级初一和高一年级2 202名在校中学生进行2次问卷调查。基线调查2 160名中学生,1 a后随访调查2 118名中学生,随访率为98.1%。结果随访共检出抑郁症状学生974名,检出率为46.0%,其中轻、中、重度抑郁的比例分别为29.4%,13.4%和3.3%。父母为初中及以下文化程度的中学生SDS标准总分、抑郁症状检出率均最高,且中度及重度抑郁症状所占比例也较高。多因素Logistic回归分析显示,父母受教育程度均与中学生的抑郁症状呈负关联,仅父亲受教育程度差异有统计学意义。结论父母受教育程度尤其是父亲受教育程度是中学生抑郁症状的重要影响因素。     

预测模型研究的偏倚风险和适用性评估工具解读

本文介绍了预测模型研究的偏倚风险和适用性评估工具PROBAST（Prediction model Risk Of Bias ASsessment Tool）的主要内容、评价步骤和相关注意事项。PROBAST从研究对象、预测因素、结局和分析4个领域共20个信号问题对原始研究的设计、实施和分析过程中可能产生的偏倚风险和适用性进行评价。通过综合分析，对原始研究每个领域和整体的偏倚风险和适用性做出判断，分为高、低或不清楚。PROBAST为个体预测模型开发、验证和更新提供了可靠的新评价工具，它不仅可以用于预测模型的系统综述，也可作为预测模型研究通用的方法学评价工具。     

Predicting quality of life impairment in chronic schizophrenia from cognitive variables

Background The aim of this study was to see whether and how cognition deficit predicts quality of life impairments in schizophrenia patients. Method The Computerized Cambridge Automated Neuropsychological Test Battery, the Quality of Life Enjoyment and Satisfaction Questionnaire (Q-LES-Q) and the Quality of Life Scale (QLS) were used to assess 62 patients with chronic schizophrenia. Step-wise multiple regression analysis was used in order to determine cognitive variables that would predict the scores of each Q-LES-Q and QLS domain scores. Results Regression analysis revealed a significant association of the cognitive deficits with both general and domain-specific quality of life impairment measured with Q-LES-Q and QLS. Deficits in executive functions, visual sustained attention, memory and motor skills have been found to be valid predictors both before and after controlling for the severity of symptoms, emotional distress, side effects, age, education, and illness duration. Conclusions This study suggests that deficits in executive functioning, attention, memory and motor skills substantially contributes to predicting impairments across a wide range of HRQL domains, and, consequently, to quality of life appraisal in schizophrenia. Cognitive predictors cannot be attributed to illness-related and background variables. It can be concluded that, when aiming at the improvement of quality of life in schizophrenia patients, cognitive functioning should be targeted.