Institute of Occupational Medicine, RWTH Aachen University, Germany.
J Occup Health. 2011;53(1):16-22. doi: 10.1539/joh.l10061. Epub 2010 Nov 10.
In a cohort study non-response might lead to a biased selection of cohort members and may affect the validity and reliability of the study outcome. To detect the possible effects of a non-response bias on study results, we evaluated the reasons for non-participation and the differences of respondents and non-respondents in a health surveillance program for power industry workers, formerly exposed to asbestos.
A cohort of former power plant workers was formed to participate in an early detection program for lung cancer. We evaluated the results of 1,019 individuals (mean age 66 yr), of which 839 took part in at least one examination, 180 refused to participate or did not respond. To obtain the reasons for non-response, we interviewed the cohort members by telephone or we requested them by mail to complete and return a brief questionnaire. Further sources of information were the communal registration offices and local health offices.
The main reasons for non-participation were refusal (35%), illness (23.3%), death (16.7%) and difficulties with traveling (13.3%). It was impossible to make contact with or obtain an explanation from 11.7%. In a logistic regression model we demonstrated that advanced age and a long travel distance from the study center negatively affected the participation rate (p<0.001). There was no difference between respondents and non-respondents regarding prevalence (p=0.559) and incidence of lung cancer (p=0.882).
We concluded that in our cohort non-participation did not cause a selection bias in terms of lung cancer rates.
在队列研究中，无应答可能导致队列成员的选择偏倚，并可能影响研究结果的有效性和可靠性。为了检测无应答偏倚对研究结果的可能影响，我们评估了在一项针对曾接触石棉的电力行业工人健康监测计划中，不参与者的不参与原因以及与应答者和不应答者之间的差异。
我们组建了一个前发电厂工人队列，以参与肺癌早期检测计划。我们评估了 1019 名个体（平均年龄 66 岁）的结果，其中 839 人至少参加了一次检查，180 人拒绝参与或未回复。为了获得无应答的原因，我们通过电话采访了队列成员，或通过邮件请求他们填写并返回一份简短的问卷。进一步的信息来源是社区登记处和当地卫生办公室。
不参与的主要原因是拒绝（35%）、患病（23.3%）、死亡（16.7%）和旅行困难（13.3%）。无法与 11.7%的人取得联系或获得解释。在逻辑回归模型中，我们表明年龄较大和距离研究中心较远会对参与率产生负面影响（p<0.001）。应答者和不应答者之间在肺癌的患病率（p=0.559）和发病率（p=0.882）方面没有差异。
我们的结论是，在我们的队列中，不参与不会导致肺癌率的选择偏倚。
