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Aging Clin Exp Res. 2011 Jun;23(3):236-40. doi: 10.3275/7252. Epub 2010 Sep 1.

A controlled trial of envelope colour for increasing response rates in older women.

Author information

1
York Trials Unit, Department of Health Sciences, University of York, Heslington, York, YO10 5DD, UK. nm513@york.ac.uk

Abstract

BACKGROUND AND AIMS:

Postal questionnaires are widely used in health research to provide measurable outcomes in areas such as quality of life. Participants who fail to return postal questionnaires can introduce non-response bias. Previous studies within populations over the age of 65 years have shown that response rates amongst older people can be 60% or less. The current study sought to investigate whether envelope colour affected response rates in a study about the effectiveness of screening older women for osteoporosis.

METHODS:

A total of 2803 eligible female participants aged between 70 and 85 were sent an invitation pack from their GP practice. The invitation was either in a brown or white envelope and contained a matching pre-paid reply envelope. A study questionnaire was also sent out in brown or white envelopes 1 week after consenting to participate in the trial.

RESULTS:

The overall response rate was 78%. There was little evidence of an effect of envelope colour on response to the invitation to participate in the trial (OR 1.04, 95% CI 0.87-1.24). Similarly, there was no influence of envelope colour on the number of participants returning their questionnaires (OR 0.99, 95% CI 0.60-1.63). There was weak evidence of an effect of envelope colour on the response rates of the consent process (OR 0.86, 95% CI 0.74-1.00). When we updated a recent meta-analysis with the results of this study, there was a non-statistically- significant trend for greater response rates with brown envelopes compared with white envelopes (OR 1.19, 95% CI 0.86-1.64, I2=92%). However, the results where influenced by one study and when this study was excluded the pooled estimate was 0.98 (95% CI 0.89-1.08, I2=0%).

CONCLUSION:

This study found no evidence to suggest envelope colour has an effect on response to participate in a trial or questionnaire returns. There is weak evidence to suggest envelope colour may affect consent into a trial.

PMID:
20811168
DOI:
10.3275/7252
[Indexed for MEDLINE]

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