Provision of educational events and subsequent questionnaire response rates in a large-scale birth cohort study from Japan

Objectives We examined whether providing educational events for participants in a birth cohort study would increase the response rates of study questionnaires. Design Birth cohort study. Setting Questionnaires were distributed and returned by post twice in 1 year. We developed and implemented two educational sessions; a Baby Food lecture for mothers with children around 8 months old (analysis 1) and a Eurythmic session for mothers with children around 1 year and 8 months old (analysis 2). Mothers with children over the target ages were not invited (not-invited group). The invited participants were divided into three groups: those who did not apply to attend (not-applied group), those who applied but did not attend (applied group), and those who applied and attended (attended group). Participants The participants were 5379 mother–child pairs registered with the Toyama Regional Center of the Japan Environment and Children’s Study (JECS). Outcome measure The outcome measure was return of the JECS questionnaire for 1 year old sent out after the Baby Food lecture and the JECS questionnaire for 2 years old sent out after the Eurythmic session. The questionnaires were returned to us by post. Results The response rate for the attended group of the Baby Food lecture was 99.7%, and the odds ratio (OR) was significantly higher for this group than for the not-invited group (crude OR 24.54; 95% confidence interval (CI) 3.42 to 176.13; analysis 1). After the exclusion of participants who had previously attended the Baby Food lecture, the response rate for the attended group of the Eurythmic session was 97.8%, and the OR was significantly higher for this group than for the not-invited group (adjusted OR 5.66; 95% CI 1.93 to 16.54; analysis 2). Conclusion Providing educational events that are appropriate to the age and needs of the participants may increase questionnaire response rates in birth cohort studies. Trial registration number UMIN 000030786.