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.