Indoor factors and behavioural problems in children: the GINIplus and LISAplus birth cohort studies.

Indoor microbial agents exposure is associated to depressive symptoms in adults and persistent exposure to indoor mould is associated to poorer cognitive function in children. In our study, we aimed to assess the effects of the exposure to indoor factors associated with increased microbial exposure (mould, dampness and pets) on behavioural problems in children aged 10 years, participating in two German birth cohorts. A total of 4860 children were followed until the age of 10 years, and the strengths and difficulties questionnaire (SDQ) was administered to the parents. Indoor factors were assessed through parental reported questionnaires in periodical surveys. Logistic and multinomial regressions adjusting for potential confounders were performed. Prevalences of borderline/abnormal total scores in the SDQ at 10 years of age were higher in children exposed to mould (aOR=1.23, 95%CI=1.00-1.56), dampness (aOR=1.51, 95%CI=1.10-2.07), and pets (aOR=1.48, 95%CI=1.20-1.94). The dimension "emotional symptoms" showed statistically significant risk estimates for mould and pets, meanwhile "conduct problems" and "hyperactivity/inattention" dimensions only did for pets. No significant associations were found for the "peer relationship problems" dimension. We found a significant strong interaction between dampness and pet, the risk of borderline/abnormal scores in the "total difficulties" scale and the "emotional symptoms" dimension for pets' was at least twice the risk in children with reported dampness than in children without. Our findings point to a potential effect of microbial exposure on children's behavioural problems, especially on emotional disorders, probably mediated through neurotoxicity and immune system activation.