A Nested Randomised Controlled Trial of a Newsletter and Post-it Note Did not Increase Postal Questionnaire Response Rates in a Falls Prevention Trial

Background: Attrition (i.e. when participants do not return the questionnaires)is a problem for many randomised controlled trials. The resultant loss of dataleads to a reduction in statistical power and can lead to bias. The aim of thisstudy was to assess whether a pre-notification newsletter and/or a handwrittenor printed Post-it® note sticker, as a reminder, increased postal questionnaireresponse rates for participants of randomised controlled trials.Method: This study was a factorial trial embedded within a trial of afalls-prevention intervention among men and women aged ≥65 years underpodiatric care. Participants were randomised into one of six groups: newsletterplus handwritten Post-it®; newsletter plus printed Post-it®; newsletter only;handwritten Post-it® only; printed Post-it® only; or no newsletter or Post-it®.The results were combined with those from previous embedded randomisedcontrolled trials in a meta-analysis.Results: The 12-month response rate was 803/826 (97.2%) (newsletter 95.1%,no newsletter 99.3%, printed Post-it® 97.5%, handwritten Post-it® 97.1%, noPost-it® 97.1%). Pre-notification with a newsletter had a detrimental effect onresponse rates (adjusted odds ratio (OR), 0.14; 95% CI, 0.04 to 0.48; p<0.01)and time to return the questionnaire (adjusted hazard ratio, 0.86; 95% CI, 0.75to 0.99; p=0.04). No other statistically significant differences were observedbetween the intervention groups on response rates, time to response, and theneed for a reminder.Conclusions: Post-it® notes have been shown to be ineffective in threeembedded trials, whereas the evidence for newsletter reminders is stilluncertain.KeywordsRandomised controlled trial; randomisation; embedded trial; newsletter;Post-it® note; response rate