Baumann A, Stieber J, Löwel H
GSF-Institut für Epidemiologie, Neuherberg.
Gesundheitswesen. 1997 Apr;59 Suppl 1:19-25.
In prospective cohort studies losses to follow-up are the major source of bias. This article describes the results of the investigation whether there are systematic differences in socio-economic and health-related factors between participants in a follow up study and those who are lost to follow-up. Subjects included were 1,030 men and 957 women aged 55-74 who participated in the second MONICA Survey Augsburg, F.R.G., 1989/90 (MONICA = Monitoring of trends and determinants of cardiovascular disease). They were reexamined in 1994-95. In 1994/95 910 men and 912 women of the baseline study were still alive, 1305 persons (663 men, 642 women) took part in the follow up by telephone. Altogether 120 men and 45 women had died since 1989/90. 144 persons were not eligible for the study (15 moved away, 5 severely ill persons, 124 without telephone). 373 persons were classified as eligible non-responders. The response rate was 77.8% concerning 1678 eligible persons (men 79.1%, women 76.4%). Non-response has led to an underrepresentation of the lower social class (workers, less than 10 years of education; household income less than 1500 DM) and of persons living alone (single, divorced, widowed; single-person households). In females, non-responders were overrepresented by "never employed persons" (odds ratio 3.02; 1.89-4.85). We found that the odds of being non-responder for single, divorced or widowed men was 3.40 (95 %-CI: 2.20-5.23) compared to married men. Men "without chronic diseases" at the baseline study compared with ill men had an odds for non-response of 1.54 (95%-CI: 1.00-2.37); the odds was 1.38 (95%-CI: 1.02-1.85) among women who had described their health status as "not so good/bad" in comparison with women with good self reported health. The reported distortions by non-response could be important in analyses of social conditions of morbidity and mortality. The underrepresentation of men without chronic diseases and women with bad self-assessment of their health is relevant for the estimates of morbidity as health outcome. Both aspects have to be taken into account in the interpretation of the results.
在前瞻性队列研究中，失访是偏差的主要来源。本文描述了一项调查结果，即随访研究中的参与者与失访者在社会经济和健康相关因素方面是否存在系统性差异。纳入的研究对象为1030名男性和957名女性，年龄在55 - 74岁之间，他们参与了1989/90年在联邦德国奥格斯堡进行的第二次MONICA调查（MONICA = 心血管疾病趋势和决定因素监测）。他们在1994 - 1995年接受了再次检查。在1994/95年，基线研究中的910名男性和912名女性仍然存活，1305人（663名男性，642名女性）通过电话参与了随访。自1989/90年以来，共有120名男性和45名女性死亡。144人不符合研究条件（15人搬走，5人重病，124人没有电话）。373人被归类为符合条件的无应答者。针对1678名符合条件的人（男性79.1%，女性76.4%），应答率为77.8%。无应答导致社会较低阶层（工人，受教育年限少于10年；家庭收入低于1500德国马克）和独居者（单身、离婚、丧偶；单人家庭）的代表性不足。在女性中，“从未就业者”在无应答者中占比过高（优势比3.02；1.89 - 4.85）。我们发现，与已婚男性相比，单身、离婚或丧偶男性成为无应答者的几率为3.40（95%置信区间：2.20 - 5.23）。在基线研究中“无慢性病”的男性与患病男性相比，无应答几率为1.54（95%置信区间：1.00 - 2.37）；与自我报告健康状况良好的女性相比，将自己的健康状况描述为“不太好/差”的女性无应答几率为1.38（95%置信区间：1.02 - 1.85）。所报告的无应答导致的偏差在发病率和死亡率的社会状况分析中可能很重要。无慢性病的男性和对自身健康自我评估较差的女性代表性不足，这与作为健康结果的发病率估计相关。在解释结果时必须考虑这两个方面。
