Asking questions changes health-related behaviour: An updated systematic review and meta-analysis.

OBJECTIVE: The question-behaviour effect refers to whether asking people questions can result in changes in behaviour. Such changes in behaviour can lead to bias in trials. This study aims to update a systematic review of randomised controlled trials investigating the question-behaviour effect, in light of several large pre-registered studies being published. STUDY DESIGN AND SETTING: A systematic search for newly published trials covered 2012 to July 2018. Eligible trials randomly allocated participants to measurement versus non-measurement control conditions or to different forms of measurement. Studies that reported health-related behaviour as outcomes were included. RESULTS: Forty-three studies (33 studies from the original systematic review and 10 new studies) compared measurement versus no-measurement. An overall small effect was found using a random effect model: SMD = 0.06 (95% CI 0.02-0.09), n= 104,388. Statistical heterogeneity was substantial (I2 =54%). In an analysis restricted to studies with a low risk of bias, the QBE remained small but significant. There was positive evidence of publication bias. CONCLUSION: This update shows a small but significant question-behaviour effect in trials with health-related outcomes, but with considerable unexplained heterogeneity. Future trials are needed with lower risk of bias are needed, with pre-registered protocols and greater attention to blinding.