Objective We previously found that administering a pre-screening lifestyle questionnaire lowered the subsequent attendance proportion in the first-ever colorectal cancer screening. We sought to determine whether the effect continued in subsequent screening rounds. Methods The eligible survey cohort ( n = 10,375) received a follow-up questionnaire in 2012, and in 2013, they were invited for colorectal cancer screening for the second time. For the third screening round, in 2015, no questionnaires were sent in the previous year. Screening attendance in 2013 and in 2015 was examined in relation to survey mailings. Results The colorectal cancer screening attendance rate in 2013 was 58.4% in the survey population, and 63.9% in those not surveyed ( P < 0.001). In 2015, the screening attendance rate was 61.7% among those who had been sent the questionnaires in 2010 and in 2012, and 66.2% in those not surveyed ( P < 0.001). The reduction in screening attendance was greater at the second (2013) round than at the first (2011). Conclusion The effect of the initial survey seemed to continue even when no questionnaires were being sent. Attendance among those who had been sent questionnaires earlier did not reach the level of the group that was never surveyed.
Keywords: Colorectal cancer screening; attendance; mass screening; questionnaires; research intervention.