ZusammenfassungIn recent years, the problem of decreasing response in population-based research has received considerable attention (e.g., 1, 2-5) and although its implications are still a matter of debate (e.g., 6, 7-11), there seems to be a consensus that a higher response is generally preferable (e.g., 5, 10). A systematic review by Edwards and colleagues (12) reported that already some low-level characteristics of the delivery (e.g., recorded or first-class delivery, hand-written addresses) can increase the response to a mailed survey. The color of envelope (brown vs. white) did not influence the response (12) but may do so in other cultural contexts. We compared the response to grey vs. white envelopes that we used for invitations to a large cohort study in Germany. Grey envelopes are commonly used by German official authorities and we assumed that a more official character might influence the recipient’s attitude towards the contents of the letter. The response might also be influenced the by fact that grey envelopes apparently are made from recycled paper, whereas the paper source is not obvious for white envelopes. In this trial, embedded in the German National Cohort (GNC, German: NAKO Gesundheitsstudie; 13), we investigated whether the envelope color of the first invitation influenced the probability of a reply to the invitation, the delay between mailing date and replies, and, finally, the probability of study participation. 1. Galea S, Tracy M. Participation rates in epidemiologic studies. Ann Epidemiol 2007;17(9):643-53. 2. Groves RM. Nonresponse Rates and Nonresponse Bias in Household Surveys. Public Opinion Quarterly 2006;70(5):646-75. 3. La Verda N, Teta MJ. Re: "Reporting participation in epidemiologic studies: a survey of practice". Am J Epidemiol 2006;164(3):292. 4. Morton LM, Cahill J, Hartge P. Reporting participation in epidemiologic studies: a survey of practice. Am J Epidemiol 2006;163(3):197-203. 5. Stang A. Nonresponse research--an underdeveloped field in epidemiology. Eur J Epidemiol 2003;18(10):929-31. 6. Jöckel KH, Stang A. Cohort studies with low baseline response may not be generalisable to populations with different exposure distributions. Eur J Epidemiol 2013;28(3):223-7. 7. Rothman KJ, Gallacher JE, Hatch EE. Why representativeness should be avoided. Int J Epidemiol 2013;42(4):1012-4. 8. Stang A, Jöckel KH. Studies with low Response Proportions may be less biased than Studies with high Response Proportions. American Journal of Epidemiology 2004;159(2):204-10. 9. Groves RM, Couper MP, Presser S, et al. Experiments in Producing Nonresponse Bias. Public Opinion Quarterly 2006;70(5):720-36. 10. Lacey JV, Jr., Savage KE. 50 % Response rates: half-empty, or half-full? Cancer Causes Control 2016;27(6):805-8. 11. Nohr EA, Frydenberg M, Henriksen TB, et al. Does low participation in cohort studies induce bias? Epidemiology 2006;17(4):413-8. 12. Edwards PJ, Roberts I, Clarke MJ, et al. Methods to increase response to postal and electronic questionnaires. Cochrane Database Syst Rev 2009(3):MR000008. 13. German National Cohort C. The German National Cohort: Aims, Study Design and Organization. Eur J Epidemiol 2014;29(5):371-82.

Schlüsselwörter-

EinrichtungenLeibniz Institute for Prevention Research and Epidemiology - BIPS, Leibniz-Institut für Präventionsforschung und Epidemiologie – BIPS, Leibniz-Institut für Präventionsforschung und Epidemiologie - BIPS, Leibniz Institute for Prevention Research and Epidemiology BIPS