Growth Trajectories and Body Composition in Preschoolers With Allergic Conditions: Findings From the Japan Environment and Children's Study Pilot Cohort

An increase in allergic diseases and obesity suggest a potential association. A systematic review indicated that persistent high body mass index (BMI) raises asthma risk in children [1]. Increased body fat was linked to diminished lung function regardless of atopic condition [2]. A randomised controlled trial showed that dietary changes can lead to rapid weight reduction in obese children with asthma, resulting in enhanced lung function and better asthma management [3]. A UK study revealed no significant evidence of a causal link between infant BMI and eczema at the age of 1 year [4]. We previously reported that eczema was related to lower stature, lower BMI and decreased weight in Japanese children [5]. Prior studies have focused on height, weight and BMI, with growing interest in body composition, including muscle and fat tissue. However, the relationship between body composition and allergic conditions remains ambiguous. This research aimed to address this gap by investigating the link between body composition and allergic diseases, particularly asthma and atopic dermatitis, from a general birth cohort in Japan. This study was a prospective multi-centre birth cohort (JECS pilot) [6]. Data collection consisted of questionnaires every 6 months from 6 months to 6 years, medical assessments, blood sampling and body composition analysis using Bioelectrical Impedance Analysis (MC-780A; TANITA, Tokyo, Japan) at 6 years old. We assessed asthma ever and rhinitis ever by the ISAAC questionnaire. Food allergy ever was defined as parental report of having a doctor's diagnosis since birth. Atopic dermatitis was assessed by a positive answer from the caregiver to the question (child at 6 years), ‘Has your child ever had atopic dermatitis?’ For the missing variables, we attempted to generate assumption data by deterministic regression imputation. Atopic dermatitis, asthma, rhinitis, food allergy, food elimination and mother's allergic history were targeted as variables. All statistical analyses were performed with EZR (ver. 1.68), a graphical user interface for R (The R Foundation for Statistical Computing, Vienna, Austria). The Ethics Committees of the National Institute for Environmental Studies and the participating institutions approved the study. Detailed methods and findings are accessible in the subsequent repository (https://doi.org/10.5281/zenodo.14449682). The study received approval from the Ethics Committees of the National Institute for Environmental Studies, where the JECS Program Office is based, as well as from all participating institutions. The follow-up rate at age 6 years was 76.8% (338/440) and children without missing values numbered 163. We followed Table 1 presents the data pertaining to the mean BMI z-score, the median skeletal muscle mass index (SMI) and the fat mass index (FMI) in subjects classified with and without allergic conditions (imputed data). The presence of atopic dermatitis at 6 years of age significantly increased the FMI median [IQR] 2.78 [0.78–4.44] vs. 2.12 [0.38–10.79], p = 0.03. There were no clear associations identified between BMI, SMI and the occurrences of atopic dermatitis, asthma, allergic rhinitis or food allergy in children. The detailed results are shown in the online repository (https://doi.org/10.5281/zenodo.14449682). In the present investigation, children afflicted with allergic diseases, including atopic dermatitis and asthma, exhibited no statistically significant disparities in BMI or SMI in comparison to their non-allergic counterparts. However, children with atopic dermatitis significantly increased FMI. In the neonatal period, increased body fat mass has been reported as a risk for the development of atopic dermatitis at 6 months and 1 year of age [7]. Although FMI could not be measured in children younger than 6 years old in the current cohort of participants, it was implicated that atopic dermatitis might be associated with FMI at the age of 6 years. This investigation is the inaugural epidemiological analysis aimed at revealing the relationship between allergic disorders and body composition factors, encompassing both SMI and FMI. The findings from our research suggest that specific allergic disorders may influence body composition. We need further investigations of the relationship between body composition and allergic inflammation. Considering that dietary restrictions can influence nutrient balance, it may be beneficial in clinical practice to perform a comprehensive evaluation of overall nutritional health, incorporating assessments of both SMI and FMI. Prior research has illustrated that the connection between BMI and the presence of wheezing and eczema was ascertained in British children [8]. Indicators of adiposity were correlated with the incidence of asthma, the severity and management of asthma and the prevalence of atopy among children residing in Puerto Rico [9]. The impact of body size and body composition is likely to differ based on racial and environmental variables and eating habits, thereby necessitating the consideration of contextual factors such as the living conditions and dietary habits of each individual child. Nevertheless, this study had several limitations. As the research concentrated on children from the general population, it was not feasible to investigate associations with the severity of allergic conditions. Furthermore, despite achieving a follow-up rate of approximately 80%, which was deemed relatively high, a significant number of children did not participate in certain outcome assessments, such as blood sampling, resulting in a diminished sample size for the analysis. To mitigate this issue, we compared the characteristics of the children included in the analysis with those excluded and utilised imputation techniques to address missing data, thereby enhancing the robustness of our findings. We suggest that atopic dermatitis might be related to body fat in children. Currently, a comprehensive birth cohort study involving 100,000 participants from the general population is underway, with the aim of corroborating the reproducibility of our findings through this anticipated research. D.H. and K.Y.-H. contributed to the study design. D.H. analysed the data and prepared the study results. D.H. and K.Y.-H. wrote the original draft of the manuscript. All co-authors contributed to the interpretation of the findings. K.Y.-H. revised the manuscript critically for important intellectual content and gave final approval for this study. All co-authors contributed to revising the manuscript and approved the final version. We sincerely want to thank all participants and the Japan Environment and Children's Study (JECS) staff. This was an exploratory study using information and samples obtained from the JECS, which is a pilot study. It was funded by the National Institute for Environmental Studies, Ibaraki, Japan. The findings and conclusions presented in this article are solely the authors' responsibility. The authors declare no conflicts of interest. The JECS was approved by the Institutional Review Board on Epidemiological Studies of the Ministry of the Environment and the ethics committees of all involved institutions. The study was carried out in compliance with the Declaration of Helsinki and the relevant national and international regulations and guidelines. The study protocol was comprehensively reviewed and approved by the respective regional research centres. Informed consent was obtained from the parents of all participants. Sharing of individual participant data is not currently available, as IRB approval has not yet been obtained under the Ethical Guidelines for Medical and Biological Research Involving Human Subjects and the Personal Information Protection Commission in Japan. Any data queries can be emailed to the Primary Investigator, Kiwako Yamamoto-Hanada, at [email protected].