Association between maternal insecticide use and otitis media in one-year-old children in the Japanese Environment and Children Study
The STROBE checklist was followed in this study.
Study design and participants
We used data from the Japanese Children’s Environment Study (JECS) in this prospective cohort study. The JECS is a national birth cohort study that investigates environmental factors that may affect the health and development of children in Japan28. The details of the JECS have been previously described29. All participants were recruited between January 2011 and March 2014. The current study used the “jecs-an-20180131” dataset, which was published in March 2018. Of these, we excluded stillbirth, abortion, missing values and multiple births.
Data regarding history of OM in the first year, breastfeeding in the first 6 months, daycare use, pneumococcal and Hib vaccine were collected from a parent self-report questionnaire. Data regarding live births or stillbirths, single or multiple births, sex, weeks of gestation, birth weight, mother’s age and whether the child was diagnosed with trisomy 21 were transcribed from medical records by physicians, midwives/nurses and research coordinators.
The primary endpoint was obtained by the “C1y questionnaire”, which asked caregivers when their children were 1 years old: “Has your child been diagnosed with OM by a doctor? The outcome variable was binomial: no diagnosis with OM as 0 and diagnosis with OM as 1. We did not distinguish between acute otitis media and otitis media with effusion in this questionnaire. Also, there was no data on how OM was treated in this questionnaire.
Exposure factors were professional use of insecticide by the mother for more than half a day from conception through the first and second/third trimesters. The question was: “How often was insecticide used professionally for more than half a day during pregnancy?” “. We obtained this information from the mother’s questionnaire “Questionnaire M-T1”, completed in the first trimester, and “Questionnaire M-T2”, completed in the second/third trimester.30. We categorized these variables as follows: No as 1, 1-3 times a month as 2, and 1-6 times a week and daily as 3.
We selected the covariates below because they were known risk factors for OM, as described in the introductory section. Although treatment of maternal infertility has not been reported to be associated with OM; primary ciliary dyskinesia, which causes both chronic OM and infertility, is hereditary31. Therefore, we selected the treatment of maternal infertility as a covariate. Other covariates included gender, weeks of gestation, birth weight, exclusive breastfeeding for the first 6 months, living with older siblings at 6 months, attending a nursery at one year of age, maternal history of chronic OM, maternal age, history of pneumococcal vaccination, and Hib vaccine, whether the child has been diagnosed with trisomy 21 or not, and a history of fertility treatment. We also selected smoking around children, such as paternal and maternal smoking habits, maternal exposure to passive smoking, and household smoking at 1 month of age. We focused on maternal occupation, especially farmers. However, the number of farmers was very low. Instead, we used broad occupational categories. We recorded the number of mothers in each major maternal occupational category.
We have classified the binomial variables as follows: sex of the child: male in 1, female in 2; living with siblings at 6 months, daycare use at 1 year, maternal history of chronic OM, history of pneumococcal vaccine and Hib vaccine, children with Down syndrome, history of fertility treatment: No like 0, yes like 1.
In addition, we categorized the categorical variables as follows: weeks of gestation32.33: 37 to 41 weeks in 1,
All statistical analyzes were performed using Stata version 15 software (StataCorp, College Station, TX, USA). First, we compared patient characteristics between the OM and non-OM background groups for the first year in children. Second, we analyzed the relationship between whether children were affected by OM in the first year and maternal use of insecticides, both from conception to the first trimester and from conception in the second/third trimesters, using logistic regression analysis. Third, we performed a sensitivity analysis by the multiple imputation method because there were many missing values. Finally, we performed a subgroup analysis of the relationship between whether children were affected by OM during the first year and maternal use of insecticides both from conception to first trimester and from conception in the second/third trimesters using a logistic regression analysis in three subgroups. . These groups included whether the children had a sibling living with them when they were 6 months old, whether the children attended daycare when they were one year old, and whether the mother had a history of chronic OM. Significance was defined as p
The JECS protocol has been reviewed and approved by the Ministry of the Environment’s Institutional Review Committee on Epidemiological Studies and the ethics committees of all participating institutions: the National Institute for Environmental Studies which leads the JECS, the National Center for Child Health and Development, Hokkaido University, Sapporo Medical University, Asahikawa Medical University, Japanese Red Cross College of Nursing Hokkaido, Tohoku University, University of Fukushima University, Chiba University, Yokohama City University, Yamanashi University, Shinshu University, Toyama University, Nagoya City University, Kyoto University, Doshisha University, Osaka University, Research Institute of Osaka Medical Center for Maternal and Child Health, Hyogo College of Medicine, University of Tottori, University of Kochi, University of Occupational Health and Environment ale, Kyushu University, Kumamoto University, Miyazaki University, Ryukyu University (Ethical Number: No. 100910001). We have confirmed that all searches were carried out in accordance with relevant guidelines/regulations. We obtained written informed consent from all participants prior to their participation in this study.