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 stillbirth; therefore, we analysed data from 9649 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 (ORs: 0.47, 95% CIs: 0.24 to 0.85), positive participation of participants’ partner (OR: 0.25, 95% CI: 0.17 to 0.35) and multiple visits to the obstetrician (OR: 0.02, 95% CI: 0.02 to 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 to 0.95 and 0.95 to 0.98 and 0.16 to 0.72, respectively); those exposed to secondary smoke had lower odds of responding (OR: 1.59, 95% CI: 1.12 to 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.
- longitudinal cohort study
- pregnant women
- birth cohort study
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Contributors MK designed and conducted the study, performed the statistical analyses and wrote the manuscript. KM helped draft the manuscript. AT conducted the data collection and helped draft the manuscript. MI and TT conducted data collection and helped critically revise the manuscript. KH and HI participated in the study design and helped critically revise the manuscript. HO assisted with the statistical analyses. YA and SS helped critically revise the manuscript. All authors have read and approved the final manuscript.
Funding The Japan Environment and Children’s Study was supported by the Ministry of the Environment, Japan. The findings and conclusions of this article are solely the responsibility of the authors and do not represent the official views of the above-mentioned government.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The dataset supporting the conclusions of this article will be available after the steering committee of the JECS allows it to become available. The dataset supporting the conclusions of this article is unsuitable for public deposition due to ethical restrictions and legal framework of Japan. The Act on the Protection of Personal Information (Act No. 57 of 30 May 2003; amendment on 9 September 2015) prohibits publicly depositing data containing personal information. Ethical Guidelines for Medical and Health Research Involving Human Subjects enforced by the Japan Ministry of Education, Culture, Sports, Science and Technology and the Ministry of Health, Labour and Welfare also restricts the open sharing of the epidemiological data. All inquiries about access to data should be sent to Dr Shoji F. Nakayama, JECS Programme Office, National Institute for Environmental Studies; email: firstname.lastname@example.org.
Collaborators Members of the Japan Environment and Children’s Study (JECS), as of 2018 (principal investigator, Toshihiro Kawamoto): Yukihiro Ohya (National Center for Child Health and Development, Tokyo, Japan), Reiko Kishi (Hokkaido Regional Center for JECS, Hokkaido University, Sapporo, Japan), Nobuo Yaegashi (Miyagi Regional Center for JECS, Tohoku University, Sendai, Japan), Koichi Hashimoto (Fukushima Regional Center for JECS, Fukushima Medical University, Fukushima, Japan), Chisato Mori (Chiba Regional Center for JECS, Chiba University, Chiba, Japan), Shuichi Ito (Kanagawa Regional Center for JECS, Yokohama City University, Yokohama, Japan), Zentaro Yamagata (Koshin Regional Center for JECS, University of Yamanashi, Chuo, Japan), Hidekuni Inadera (Toyama Regional Center for JECS, University of Toyama, Toyama, Japan), Michihiro Kamijima (Aichi Regional Center for JECS, Nagoya City University, Nagoya, Japan), Takeo Nakayama (Kyoto Regional Center for JECS, Kyoto University, Kyoto, Japan), Hiroyasu Iso (Osaka Regional Center for JECS, Osaka University, Suita, Japan), Masayuki Shima (Hyogo Regional Center for JECS, Hyogo College of Medicine, Nishinomiya, Japan), Yasuaki Hirooka (Tottori Regional Center for JECS, Tottori University, Yonago, Japan), Narufumi Suganuma (Kochi Regional Center for JECS, Kochi University, Nankoku, Japan), Koichi Kusuhara (Fukuoka Regional Center for JECS, University of Occupational and Environmental Health, Kitakyushu, Japan), and Takahiko Katoh (South Kyushu/Okinawa Regional Center for JECS, Kumamoto University, Kumamoto, Japan).
Patient consent for publication Obtained.
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