Electronic reminders did not improve postal questionnaire response rates or response times: a randomized controlled trial.

OBJECTIVE: We aim to evaluate the effectiveness of electronic reminders (ERs) to improve the response rates and time to response of postal questionnaires in a health research setting. STUDY DESIGN AND SETTING: This pragmatic randomized controlled trial (RCT) was nested within a multicenter RCT of yoga for lower back pain. Participants who provided an electronic mail address and/or mobile phone number were randomized to receive an ER or no reminder (controls) on the day they were due to receive a follow-up questionnaire. RESULTS: One hundred twenty-five participants (32 males and 93 females) mean age 46 (standard deviation: 11, range: 20-65) were randomized to ER (n=62) or controls (n=63). Overall 85.6% of participants returned postal questionnaires (87.1% ER group and 84.1% from controls). No significant differences were found between the two groups for response rate (difference between groups=3.0%, 95% confidence interval [CI]=-10, 16; P=0.64) or time to response after adjusting for age, gender, and treatment allocation (χ(2) ([3df])=7.10; P=0.07). CONCLUSION: In the present RCT, we found little evidence for the effectiveness of ERs to increase response rates or time to respond for the return of questionnaires in this study population group.