Harnessing the question-behavior effect to enhance colorectal cancer screening in an mHealth experiment

Objectives. To assess whether asking questions about a future behavior changes this behavior (i.e., the question-behavior effect) when applied to a population-level intervention to enhance colorectal cancer screening. Methods. In 2013, text-message reminders were sent to a national sample of 50 000 Israeli women and men aged 50 to 74 years following a fecal occult blood test invitation. Participants were randomized into 4 intervention groups (2 interrogative reminders, with or without reference to social context; 2 noninterrogative reminders, with or without social context) and a no-intervention control group. The outcome was fecal occult blood test uptake (n = 48 091, following attrition). Results. Performance of fecal occult blood test was higher in the interrogative-reminder groups than in the other 3 groups (odds ratio = 1.11; 95% confidence interval = 1.05, 1.19); the effect size was small, varying in the different group comparisons from 0.03 to 0.06. Conclusions. The question-behavior effect appears to be modestly effective in colorectal cancer screening, but the absolute number of potential screenees may translate into a clinically significant health promotion change.