Lifestyle behaviors and home and school environment in association with sick building syndrome among elementary school children: a cross-sectional study

This study analyzed data from a questionnaire survey conducted to assess the home and/or school environments of elementary school children in Sapporo, Japan. As the survey design has been reported in detail elsewhere [19], only brief descriptions are provided here.

Sapporo city is located in Hokkaido, which is an island in northern Japan. There are 202 total public elementary schools in Sapporo city. Based on Health and Physical Education Council membership and to include all schools from all 10 wards of Sapporo city, a total of 35 school principals were asked to participate in this study. Of those, 12 agreed and participated in this study; student numbers ranged from 113 to 906.

The questionnaire survey was conducted from November 2008 to February 2009. The school building characteristics were obtained from either the principal or vice-principal of the respective school. We distributed a total of 6393 questionnaires to all children in grades 1–6 from those 12 schools. Classroom teachers asked students to bring these questionnaires to parents or guardians. The questionnaires were completed by parents or guardians on behalf of their children. Students returned the completed questionnaires (n = 4408 returned; response rate = 69%) back to their teacher within 5–8 days. To determine and categorize SBS symptoms, the Japanese version of the MM080 epidemiological questionnaire for home and school was used [17, 20]. The “MM” in “MM080” refers to environmental medicine (i.e., Miljo Medicine in Swedish). SBS symptoms in the last three months were categorized as follows: mucosal symptoms (itchy eye, stuffy nose, and cough), skin symptoms (dry/flushed face, scalp, and/or hands), and general symptoms (fatigue, headache, and sleep problems). Each questionnaire item (symptom) was answered using one of three responses (i.e., “yes, often (every week)”, “yes, sometimes”, and “no, never”). Each item also contained a follow-up question that was answered by selecting either “yes” or “no” (i.e., “Do you believe that the symptom is due to the child’s school or home building environment?”). This study considered responses of “yes, often (every week)” to at least one symptom in the category and answer of “yes” to the respective follow-up question as SBS positive. The allergic symptoms section of the questionnaire was based on the Japanese translated version of the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire of wheeze, rhinoconjunctivitis, and eczema [19, 21]. In this study, “Any allergies” is defined positive if a child experienced at least one of the ISAAC symptoms. The survey also asked for student demographic information, including sex, grade, parental history of allergies (history of doctor-diagnosed allergies of either mother or father of the child), lifestyle behaviors, and housing characteristics. Any response to a given lifestyle behavior that was considered “unhealthy” received 1 score, while a “healthy” response received 0 score. There were seven total lifestyle behaviors, (i) breakfast eating habits (sometimes or never = 1, always = 0), (ii) faddiness (like/dislike of food; significant = 1, none/some = 0), (iii) TV watching time/day (≥ 3 h = 1, ≤ 2 h = 0), and (iv) constipation/bowel movement (once or less in 3 days = 1, once every 1–2 days = 0). Next, three sleep-related item responses, namely (v) sufficiency, (vi) feeling refreshed after sleep, and (vii) deep sleep was used to subjectively evaluate “poor” or “good” sleep habits. Responses of “no or sometimes” were considered indicative of poor sleep quality and received 1 score, while “almost or always” were considered indicative of good sleep quality and thus received 0 score. We also assigned a lifestyle index to reflect a given student’s lifestyle behaviors based on their responses; this ranged from 0 (healthiest) to 7 (unhealthiest or least healthy). Parents of the child answered a children’s home building characteristics questionnaire, which included items on the number of inhabitants, building age, housing type (single- or multifamily house), structure (wood/other), newly built or renovated within 1 year (yes/no), whether they lived near heavy traffic road (within 50 m; yes/no), whether there was mechanical ventilation in the living area and/or child’s room(s) (yes/no), the presence of environmental tobacco smoke (ETS; yes/no), the presence of wall-to-wall carpet (yes/no), and whether there were furry pets in the house (yes/no). We also inquired about four signs of dampness, including visible mold, moldy odor, episodes of water leakage, and condensation within the past five years; here, answers of “yes” received one score each, thus resulting in a total score used for the dampness index (0–4), with higher scores indicating greater dampness [1].

This study’s protocol was approved by the ethical board for epidemiological studies at the Hokkaido University Graduate School of Medicine on September 24, 2008. Written consent was obtained from the guardian/parent of each participating child.

We compared the results from this study’s population (Sapporo City) with those reported by a study among elementary school children in the Japanese city of Asahikawa (135 km from Sapporo City) [17]. Here, this study’s population showed lower prevalence rates for mucosal (6.9% vs 14.0%), skin (2.0% vs 11.3%), and general symptoms (0.8% vs 4.8%) [17]. Children in the Asahikawa study skipped breakfast more often and consumed greater amounts of snacks/sweets [17]. Thus, better (healthier) lifestyle habits may have partially contributed to the lower prevalence of SBS symptoms found among the current study’s population. This study also found a higher prevalence of general symptoms among girls when compared to boys. A previous study based in Iran school also found more symptoms among female students [22], while another Japanese school children study reported more symptoms among boys [17]. On the other hand, studies among adult populations have reported higher SBS rates among women [23‐25]. As such, there is not yet sufficient evidence to establish gender-specific differences for SBS rates. Thus, future studies should investigate this issue more thoroughly.

This study also found positive associations between mucosal and skin symptoms and the presence of allergies (wheeze, rhinoconjunctivitis, and eczema), thus supporting previous findings [13, 14, 26]. We therefore hypothesized that children with asthma/allergies are at greater danger for developing SBS symptoms than those without these conditions. Notably, similar SBS trends were observed in our stratified analysis of allergic and non-allergic children except in eating breakfast and TV watching variables with mucosal symptoms (Supplementary Table 1), in which asthmatic children who skipped breakfast displayed increased OR, while in contrast showed lower OR in daily TV watching variable when compared to non-asthmatic children in mucosal symptoms. This indicates that SBS may be experienced in children independent of allergic symptoms. This could be attributed to factors other than allergic diseases, such as indoor environmental pollutants (e.g., dampness, chemicals, and/or microbial factors), which may increase SBS in non-allergic children [1, 8, 10, 11, 27]. Further, our stepwise analysis revealed that the presence of any allergies (an independent variable) was associated with mucosal and skin symptoms (Table 5), which also supported previous studies [13, 26]. Thus, the risk of SBS might be decreased by making efforts to prevent allergic diseases in children.

One of this study’s main objectives was to evaluate the prevalence of SBS and its association with children’s lifestyle behaviors. While only 2.4% reported skipping breakfast, these children showed significantly increased general symptoms when compared to children who always eat breakfast. Further, significant faddiness was also associated with increased mucosal and general symptoms. A stepwise analysis indeed confirmed that significant faddiness and constipation (independent variables) were related to mucosal and general symptoms, respectively. This supports previous studies reporting that similar unpreferable eating behaviors were adversely associated with eye and general symptoms in children [17, 18]. Further, non-parametric Spearman significant correlation was observed between unpreferable eating habits (skipping breakfast and exhibiting faddiness) and constipation (Supplementary Table 2). This supports the findings of a previous study showing that individual’s food consumption habits were closely related to bowel movement frequency [28]. Thus, unhealthy food consumption behaviors such as skipping breakfast may help explain the increased OR observed between SBS symptoms and constipation in this study. This indicates the importance of promoting healthy eating behaviors for young children when attempting to reduce SBS and mitigate other health risks in later life.

It is well-established that healthy sleep habits are essential for child health and development [29]. We therefore independently investigated the effects of three sleep qualities (i.e., sufficiency, feeling refreshed after sleep, and deep sleep) on SBS. Here, results showed increased ORs for poor quality in all three items, thus supporting a study by Isshiki et al. [18], which found that children who slept longer and more sufficiently reported less general SBS symptoms. Notably, this study’s sleep index (0–3) values showed increased ORs with each additional poor sleep quality variable and the presence of all SBS with p for trend < 0.001 (Supplementary Table 3). This indicates that children with more than one sleep problem may be at greater risk for developing SBS symptoms.

More than 50% of the respondent’s homes in this study were positive for one or more dampness indicators. Notably, we found a significant association between dampness index (0–4) values and SBS symptoms, which also supports previous studies [1, 10, 17, 26, 27]. Specifically, our stepwise analysis in Table 5 confirmed a persistent and significant association between dampness index (0–4) and all SBS symptoms, thus indicating that dampness is the most common independent indoor variable for SBS. This directly shows that reducing dampness in the home may decrease the development of SBS symptoms. Multifamily homes, lack of ventilation, and wall-to-wall carpet were important significant home building characteristics in association with general and mucosal SBS. Studies have reported the relationship of no ventilation and wall-to-wall carpeting of home, school, or in office buildings with SBS in children or adults [27, 30, 31]. This could reflect the abovementioned common variables in different building types such as home, school, or office are related to SBS. We also found that living near roads with heavy traffic was associated with mucosal symptoms in children. This may be due to higher amounts of outdoor pollutants such as particulate matter and nitrogen oxide, in which previous studies have reported in association with SBS [32]. Although previous studies reported the association of school environments with SBS in students, in this study, we did not observe significant differences in the prevalence of SBS among schools.

This study had strengths and limitations. Strength-wise, we analyzed a relatively large number of participants (n = 4408) when compared to previous survey studies which assessed SBS symptoms among school children. Further, a stepwise analysis allowed us to elucidate the associations between independent variables and SBS symptoms, while data on personal characteristics, lifestyle behaviors, and building characteristics allowed us to assess several variables related to SBS in children. Although home environment, such as dampness, may differ across Japan [1], this study population of children in municipal schools strengthens the generalizability of our findings on the prospect of covering wide school locations and small lifestyle disparity among Japanese children in municipal schools. This study solely was dependent on a parent-reporting subjective questionnaire in which the lack of observational data is one of our limitations. Another limitation of this study is our initial aim of considering both school building and home building together in relation to SBS in children with the follow-up question. Since our preliminary analysis showed no significant difference in the prevalence of SBS symptoms among schools, we investigated home building variables in association with SBS symptoms but included schools in adjusted regression models as covariate factor. In doing this, we consider both home and school environment as an independent factor, yet we could not isolate if the SBS occurs in the school building or home building. Although previous studies reported socioeconomic status (SES) as a confounding factor in association with SBS [1, 33], not obtaining SES data is our study limitation. Finally, this study is limited by its cross-sectional epidemiological design, meaning our results cannot be used to establish causal relationships.