Background/aim The immune system and gut microbiota may play a role in the cognitive development. The home microbiota are a source of microbial exposure affecting immunological and maybe gut microbiota development. Thus, it may contribute to cognitive development. Here, we assess the association between early life home dust microbial diversity and hyperactivity/inattention symptoms at 10 and 15 years old.

Methods A random sample enriched with subjects with hyperactivity/inattention at age 15 years were selected from the German LISA birth cohort. Bedroom floor dust samples were collected at age 3 months and bacterial diversity was defined by richness (number of OTUs and Chao1) and diversity indices (Shannon and Simpson) calculated from Illumina MiSeq sequencing data of 16S rRNA gene DNA amplicons. Hyperactivity/inattention was defined based on the scores of the Strengths and Difficulties questionnaire (SDQ) at ages 10 (filled by parents) and at 15 years (self-administered), using a cut-off ≥7. With adjusted logistic regression models we investigate the associations between symptoms and 4 diversity indices in tertiles. At age 10, models were weighted by the inverse of the sampling weights.

Results We included 226 individuals with information on indoor microbial diversity and hyperactivity/inattention symptoms. The median values of the diversity indices were higher among children without symptoms at age 10 for bacteria and at age 15 for fungi. After adjustment, hyperactivity/inattention at age 10 was inversely associated with bacterial richness (number of observed OTUs medium vs low diversity: OR=0.4; CI: 0.2 to 0.8; Chao1 medium vs low diversity: OR=0.3; CI: 0.1 to 0.5; high vs low: OR=0.3; CI: 0.2 to 0.6), and positively associated with fungal Chao1 (high vs low: OR=2.1; CI: 1.1 to 4.0), Shannon (medium vs low: OR=2.8; CI: 1.3 to 5.8), and Simpson (high vs low: OR=4.7; CI: 2.4 to 9.3). No significant associations were observed between the indices and hyperactivity/inattention at age 15.

Conclusion Our results suggest that early life exposure to microbial diversity may play a role in the development of hyperactivity/inattention during childhood. Exposure to rich bacterial environment may protect from developing hyperactivity/inattention, while high fungal diversity may have the opposite effect. Further larger studies are needed to confirm our results.