The Association of Autism Spectrum Disorders and Symptom of Asthma, Allergic Rhinoconjunctivitis and Eczema among Japanese Children Aged 3-6 Years

There is insufficient epidemiological evidence on the relationship between autism spectrum disorder (ASD) and allergic diseases. We performed a cross-sectional survey to elucidate the associations between them using validated screening tools. The participants were children aged 3 - 6 years attend-ing kindergarten or nursery school in Shika Town, Japan (n = 417; valid response rate = 80.4%). Autism spectrum features were scored on the Social Communication Questionnaire (SCQ). Allergic symptoms (asthma, allergic rhinoconjunctivitis, and eczema) were determined according to the criteria of the International Study of Asthma and Allergies in Childhood. A total of 15 children (4.5%) had an SCQ score of 11 points or higher. The prevalence of symptoms was 14.7% for asthma, and 5.3% for allergic rhinoconjunctivitis, and


Introduction
Autism spectrum disorder (ASD) is a group of developmental disorders characterized by both persistent deficits in social communication and social interaction across multiple contexts and restricted, repetitive patterns of behavior, interests, or activities [1]. The aforementioned symptoms must also be present in the early developmental period. On the other hand, allergies are hypersensitivity disorders of the immune system in which both innate and acquired immunities may contribute to the development of allergic diseases (i.e., asthma, allergic rhinoconjunctivitis and eczema) [2] [3]. Although the cause of ASD remains unknown in many cases [4], recent observational studies have demonstrated that allergic diseases were more frequently seen in children with ASD compared to typically developing children, suggesting involvement of environmental factors in the development of both diseases [5]- [10]. For example, our previous study [11] found a significant association between nasal allergy and high autism score using the Autism Screening Questionnaire (ASQ) among Japanese children aged 3 -5 years old [12]. An analysis of the National Health Insurance Database in Taiwan by Chen et al. revealed that atopic diathesis in early childhood elevated the future risk of developing ASD [13]. A meta-analysis by Miyazaki et al. reported that there was a significantly higher estimated prevalence of asthma and allergic rhinoconjunctivitis in children with ASD compared to typically developing children [14]. However, in an American study, Jyonouchi et al. reported that an ASD group was not associated with atopic/non-atopic asthma, allergic rhinitis, and atopic dermatitis [5]. The controversial reports in the literature and limited epidemiological evidence therefore render the association between allergic disease and ASD unclear.
Although the prevalence of ASD remains unknown in Japan due to the lack of large epidemiological studies, the prevalence of ASD is estimated to be on the increase all over the world [15]. It is estimated that the prevalence of ASD is about 1.5% of children in the U.S. [16], and 2% of children in the general population in Korea [17]. The prevalence of allergic diseases has also increased rapidly over the last few decades in developing countries, including Japan [18] [19]. Therefore, the concomitant increases of both ASD and allergic diseases represent a potentially important and unique public health burden.
Until now, prevalence and risk factors for allergic diseases have been studied extensively in school age children but there is little information about younger children. Moreover, few epidemiological studies have examined the association  [17]. Moreover, in a Japanese nationwide survey of adults with high-functioning ASD, they were first diagnosed at an average age of 10 years [20]. Thus, there is a high probability of missing possible ASD cases if employing only the diagnosed cases in surveying early childhood morbidity. In addition, comprehensive diagnostic assessment is often expensive and time-consuming work completed by a multidisciplinary team of professionals [21], and this can be stressful for children being assessed as well as their parents. Screening method improvements could thusly decrease the specific problem of diagnostic bias due to gaps in socioeconomic status or access to medical services [22] [23].
In this paper, we describe the prevalence of symptoms of asthma, allergic rhinoconjunctivitis and eczema and clarify the association between allergic symptoms and autism spectrum features. Data were gathered with an epidemiological approach using validated screening tools in rural, Japanese, preschool-aged children (3 -6 years We hypothesized that the prevalence of allergic symptoms would be higher in children with autistic spectrum features than those without. We also investigated potential risk factors associated with allergic symptoms and ASD, including sex, age, and body mass index (BMI). These results could serve as guidelines for prevention and treatment of allergic diseases in children with ASD.

Subjects and Sampling
Our cross-sectional questionnaire-based survey was conducted in Shika Town, Ishikawa prefecture, Japan. Shika is a rural town located in the Noto peninsula with a total population of almost 22,500. The Shika study is an ongoing popula-

Screening Tool for ASD
The SCQ lifetime Japanese version was used [24] [29]. It is a parent-report questionnaire designed to screen children who may need a more comprehensive evaluation because of possible ASD. It is composed of 38 items that assess specific ASD-related behaviors, such as communication with other children and nonverbal contact. It is based on the Autism Diagnostic Interview-Revised (ADI-R) algorithm [30], which is accepted as a standardized interview-based diagnostic instrument. The SCQ assesses the three core areas of functioning characteristic of youth with ASD; reciprocal social interaction, language and communication, and repetitive and stereotyped patterns of behavior. The SCQ is one of the most widely used and studied screening instruments for identifying individuals at risk for ASD [31] [32] [33] [34] [35]. In the Japanese version, a question on pronoun reversal is omitted because Japanese verbal language seldom uses a pronoun (i.e. "you" or "s/he"). Each item was rated on a two-point scale (0 = "no" and 1 = "yes") and the range of possible scores is 0 to 38, with higher scores indicating more autistic symptomatology. Several clinical cutoff scores of the SCQ have been suggested so far (e.g. 11, 12, 15 or higher), and researchers appear to agree optimal cut-off score is dependent upon the context and nature of the study population. Among young children, a lower cut-off score is recom- [36]. Thus, we categorized children into 2 groups: children with SCQ scores ≥ 11 as possible ASD cases and children with SCQ scores <11 as non-ASD cases.

Measurement of Allergic Symptoms
We used the Japanese version of the ISAAC written questionnaire for 6 -7 year olds [37]. ISAAC is an international epidemiological research program established in 1991 and formally closed in 2012. The questionnaire was originally developed to assess the worldwide prevalence of asthma, allergic rhinoconjunctivitis and eczema among children aged 6 -7 years in the general population and to Symptoms of asthma were estimated by positive answers to the following two questions: "Has your child ever had wheezing or whistling in the chest at any time in the past?" and "Has your child had wheezing or whistling in the chest in the past 12 months?" Affirmative answers to the following three questions were required to confirm the presence of symptoms of allergic rhinoconjunctivitis: "Has your child ever had a problem with sneezing, or a runny, or blocked nose when he/she did not have a cold or the flu?", "In the last 12 months, has your child had a problem with sneezing, or a runny, or blocked nose when he/she did not have a cold or the flu?" and "In the past 12 months, has this nose problem been accompanied by itchy/watery eyes?". Symptoms of eczema were defined as present in the case of positive responses to all the following three questions: "Has your child ever had an itchy rash which was coming and going for at least six months?", "Has your child had this rash at any time in the past 12 months?" and "Has this itchy rash at any time affected any of the following places: the folds of the elbows, behind the knees, in front of the ankles, under the buttocks, or around the neck, ears, or eyes?".

Weight Abnormalities
BMI was calculated as body weight in kilograms divided by height squared in

Statistical Analysis
We evaluated differences between variables of interest within each of the three

Ethical Approval
We obtained informed consent for study participation from the parents. All procedures performed in studies involving human participants were in accor-   ORs and 95% CIs for symptom of asthma, rhinoconjunctivitis and eczema    were shown to be statistically significantly related to asthma (Table 2). Overall, allergic rhinoconjunctivitis was not associated with SCQ classification, age, sex, and weight abnormalities.

Discussion
In 2013, we examined the prevalence of asthma, allergic rhinoconjunctivitis and D. Hori et al. Health eczema among children in kindergarten and nursery schools in Shika Town, Japan. Furthermore, we found that preschool-aged children with autism spectrum features had an increased likelihood of suffering from symptom of eczema. A statistically significant association persisted after adjusting for age, sex, and BMI categories. To our knowledge, this is the first study using validated screening measures that shows a higher prevalence of eczema symptoms in children aged 3 -6 years with autism spectrum features compared to those without. This seminal result may be due to the effective simplicity of screening tools such as the ISAAC questionnaire and SCQ. While the cross-sectional nature of the study makes a causal conclusion impossible, the theory that autism spectrum traits would be related to eczema is supported. In contrast, we did not confirm any results from recent studies which suggest that asthma or allergic rhinoconjunctivitis are associated with ASD.
Among the participants analyzed, 4.4% (n = 15) were presumed to have ASD suggesting that some cases with SCQ scores ≥ 11 were false positives. We recognized that the SCQ could not be a replacement for a clinician-verified diagnosis and we acknowledge, as illustrated in Figure 1, that it is difficult to clearly dis- and behavioral impairments and further assessment would be beneficial [48].
Thus, we considered that the prevalence subsumed borderline ASD cases, not implying a marked overestimate. The identification of undiagnosed and untreated ASD is important, with the potential to help parents increase knowledge of ASD and improve interaction with their children from earlier ages [49].
Epidemiological study of allergic symptoms using the ISAAC questionnaire among Japanese preschool age children is scarce in the literature. We compared the present results from Shika Town (asthma, allergic rhinoconjunctivitis, eczema; 14.7%, 5.3%, 11.4%) with those obtained using the same questionnaire in the Ogasawara Islands, and Setagaya, Japan. The prevalence of asthma symptoms found in this study was higher than the study of preschool children conducted in the Ogasawara Islands (asthma, 12.2%) [50]. The prevalence of three allergic disease symptoms found in this study was lower than in the study of 6-year-old school children conducted in Setagaya (asthma, allergic rhinoconjunctivitis, eczema; 18.2%, 19.7%, 19.6%) [51]. It is well known that asthma is more prevalent in urbanized areas as air pollution is one of the environmental factors that can exacerbate asthma. Differences in pollution levels might explain why the prevalence of current wheezing in Shika Town was higher than the Ogasawara Islands (less populated area) and lesser than Setagaya (one of the most populated area in Japan).
The prevalence of allergic rhinoconjunctivitis was only 5.3% in this study. The Health prevalence of allergic rhinoconjunctivitis in general population is reported to be more than 10% in recent studies of school children in developed countries [18].
Allergic rhinoconjunctivitis generally develops with gradual aeroallergen sensitization with seasonal allergens, mainly with cedar pollen or house dust mites in Japan [52]. Its prevalence peaked at 10 years old [51]. Therefore, the low prevalence of allergic rhinoconjunctivitis in this study is plausible.
Our findings are consistent with recent studies that found eczema was significantly more prevalent in children with ASD compared to children without ASD [13] [53] [54]. We could not find significant associations of autism spectrum features with asthma or allergic rhinoconjunctivitis. At present, explanations for the mechanisms driving the high prevalence of allergic diseases in children with ASD remain speculative. One possible explanation is that eczema symptoms affected SCQ total scores because the SCQ is a scale that assesses not only social interaction and communication but also behavioral symptoms. The discomfort and pain associated with allergic diseases would aggravate behavioral symptoms in children with ASD [55]. Jyonouchi pointed out that eczema tends to be underdiagnosed in ASD children because symptoms could be masked by associated behavioral problems [5]. Due to the cross-sectional design of our study, a cause-effect relationship between allergic symptoms and high SCQ score could not be determined. A future longitudinal study is therefore required to address this issue.
It should also be noted that our results suggested a significant association between obesity and asthmatic symptoms. The result is consistent with survey in Japan [56] and a meta-analysis of prospective epidemiological studies by Beuther and Sutherland showing a higher prevalence of asthma in overweight/obese people [57]. It is also well known that asthma is more likely to occur in boys compared to girls [58]. ASD has the same tendency as asthma in regard to weight abnormalities and sex: ASD is often associated with obesity and more prevalent in boys [39]  showed the inaccuracy of parentally reported weight and height for classifying preschool-aged children into BMI categories [64], in Japan, physical measurements are generally carried out monthly at preschools. Thus, we consider the BMI values in this study to be precise.

D. Hori et al. Health
Limitations of the present study other than mentioned above need to be noted. First, the main limitation of our study is the sample size of 417 children, which might not be large enough to identify significant differences of allergic symptoms between children with possible ASD and those without. The relatively small number of children with SCQ score ≥ 11 suggests type II error, which restricts the power to detect relevant predictors. A careful interpretation of our findings is required in light of this. Future investigations with a larger sample could reveal significant relationships among allergic diseases and ASD. Second, we could not measure all variables that are likely to be a confounder in the association between allergic diseases and ASD (e.g. maternal status in pregnancy, or dietary habit). Third, we could not collect data from children who did not go to preschools. Children with severe behavioral problems might have been refused admission. Fourth, there is seasonal variation in reporting of allergic symptoms even though the questions asked about symptoms during the past year [65]. Finally, the extrapolation of conclusions from our study to other ethnicities/ cultures is limited by the fact that the participants were ethnically and culturally homogeneous.

Conclusion
Despite these limitations, this is the first study that used validated screening tools to assess the association between ASD and allergic symptoms in a general Japanese early childhood population. The study adds evidence that young children with possible ASD are more likely have eczema symptoms compared to others. These seminal results offer important clues to environmental influences on ASD and allergic diseases. Future studies using larger samples with a longitudinal design are needed to better characterize the causal association between ASD and allergic diseases.