Analysis of non-respondent pregnant women who were registered in the Japan Environment and Children’s Study: a longitudinal cohort study

What is it about?

Abstract Objectives: Non-response to questionnaires in a longitudinal study reduces the effective sample size and introduces bias. We identified the characteristics of non-respondent pregnant women, and compared them with respondents in the Japan Environment and Children’s Study (JECS) during the gestational period. Design: This was a questionnaire-based, longitudinal cohort study. Setting: Questionnaires were provided by research coordinators to mothers at prenatal examinations (at obstetrics clinics) or by mail. Mothers were measured twice: during the first trimester and during the second/third trimester. Participants: Data were collected from the 10,129 participating mothers of the 10,288 children surveyed in the 2011 baseline JECS. We excluded responses from mothers who had a miscarriage or still birth; therefore, we analysed data from 9,649 participants. Primary and secondary outcome measures: Data concerning demographics, medical history, health characteristics, health-related behaviour, and environmental exposure were collected via self-administered questionnaires. The response status of participants’ partners and contact with their obstetrician were also examined. Multivariate logistic regression analysis was used to examine factors related to non-response. Results: Response was associated with living with one’s mother-in-law (odds ratio [OR]: 0.47, 95% confidence interval [CI]: 0.24–0.85), positive participation of participants’ partner (OR: 0.25, 95% CI: 0.17–0.35), and multiple visits to the obstetrician (OR: 0.02, 95% CI: 0.02–0.03). Participants who had a medical history of allergic rhinitis, had body pain, or drank alcohol had higher odds of responding (ORs: 0.68, 0.96, and 0.36, 95% CIs: 0.48–0.95, 0.95–0.98, and 0.16–0.72, respectively); those exposed to secondary smoke had lower odds of responding (OR: 1.59, 95% CI: 1.12–2.23). Conclusions: The non-response rate decreased when participants reported health-related behaviour or characteristics. Obtaining the understanding of people around each participant might help increase response rates.

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