Eaker S, Bergström R, Bergström A, Adami H O, Nyren O
Department of Medical Epidemiology, Karolinska Institutet, Stockholm, Sweden.
Am J Epidemiol. 1998 Jan 1;147(1):74-82. doi: 10.1093/oxfordjournals.aje.a009370.
Although self-administered questionnaires are major sources of information in epidemiology, comparatively little has been done to study practical aspects of design and mailing. The objective of this study was to evaluate various measures taken to increase the response rate. A questionnaire was mailed in July 1995 to a random sample (n = 2,000) of the Swedish population aged 20-79 years. Using a randomized factorial study design, the questionnaire and mailing procedures were changed in three ways: preliminary notification, length of the questionnaire, and mention of telephone contact. The overall questionnaire retrieval rate was 49%. Preliminary notification (adjusted odds ratio of receiving a completed questionnaire = 1.30, 95% confidence interval (CI) 1.08-1.56 relative to the absence of preliminary notification) and short length of the questionnaire (odds ratio = 1.24, 95% CI 1.04-1.48 relative to a long questionnaire) were both independently associated with a higher retrieval rate. Of eight possible combinations, the one comprising preliminary notification, a short questionnaire, and no mention of telephone contact gave the highest retrieval rate, 56%. The lowest retrieval rate, 40%, was observed for the combination of no preliminary notification, a long questionnaire, and mention of telephone contact. Young age, male sex, and urban residence significantly lowered the retrieval rate. Although there was a positive association between the questionnaire retrieval rate and partial nonresponse (missing answers in retrieved questionnaires), the marginal losses due to the latter did not cancel the gains by optimized mailing routines. Old age was the strongest determinant of partial nonresponse. The data provide evidence that design and mailing strategies, as well as demographic characteristics, may greatly influence the response rate of mailed epidemiologic questionnaires.
尽管自填式问卷是流行病学信息的主要来源，但在研究设计和邮寄的实际方面所做的工作相对较少。本研究的目的是评估为提高回复率而采取的各种措施。1995年7月，向年龄在20 - 79岁的瑞典人群随机样本（n = 2000）邮寄了一份问卷。采用随机析因研究设计，问卷和邮寄程序在三个方面进行了改变：预先通知、问卷长度以及提及电话联系。问卷的总体回收率为49%。预先通知（相对于未进行预先通知，收到完整问卷的调整优势比 = 1.30，95%置信区间（CI）1.08 - 1.56）和问卷篇幅短（相对于长问卷，优势比 = 1.24，95% CI 1.04 - 1.48）均与较高的回收率独立相关。在八种可能的组合中，包含预先通知、短问卷且未提及电话联系的组合回收率最高，为56%。未进行预先通知、长问卷且提及电话联系的组合回收率最低，为40%。年轻、男性以及城市居住显著降低了回收率。尽管问卷回收率与部分无应答（回收问卷中存在缺失答案）之间存在正相关，但后者造成的边际损失并未抵消优化邮寄程序带来的收益。年龄大是部分无应答的最强决定因素。数据表明，设计和邮寄策略以及人口统计学特征可能会极大地影响邮寄流行病学问卷的回复率。
