Is sibship composition a risk factor for childhood asthma? Systematic review and meta‑analysis

Background Following the“hygiene hypothesis”,the role of sibship composition in asthma and wheezing has been extensively studied,but the fndings are inconsistent.For the frst time,this systematic review and meta-analysis synthesized evidences from studies investigating the association of sibship size and birth order with risk of asthma and wheezing.Methods Fifteen databases were searched to identify eligible studies.Study selection and data extraction were performed independently by pairs of reviewers.Meta-analysis with robust variance estimation(RVE)was used to produce pooled risk ratio(RR)efect estimates from comparable numerical data.Results From 17,466 identifed records,158 reports of 134 studies(>3 million subjects)were included.Any wheezing in the last≤1.5 years occurred more frequently in infants with≥1 sibling[pooled RR 1.10,95%confdence interval(CI)1.02–1.19]and≥1 older sibling(pooled RR 1.16,95%CI 1.04–1.29).The pooled efect sizes for asthma were overall statistically nonsignifcant,although having≥1 older sibling was marginally protective for subjects aged≥6 years(pooled RR 0.93,95%CI 0.88–0.99).The efect estimates weakened in studies published after 2000 compared with earlier studies.Conclusions Being second-born or later and having at least one sibling is associated with a slightly increased risk of temporary wheezing in infancy.In contrast,being second-born or later is associated with marginal protection against asthma.These associations appear to have weakened since the turn of the millennium,possibly due to lifestyle changes and socioeconomic development.

MicroRNA-155 expression suggests a sex disparity in innate lymphoid cells at the single-cell level

MicroRNAs(miRNAs)are small noncoding RNAs that control gene expression at the post-transcriptional level,thereby serving as important cellular regulators.1 However,miRNA expression in specific human cellular subtypes,especially at the single-cell level,remains largely unexplored.In this study,a novel method called the PrimeFlow^(TM) RNA Assay2 was used to directly monitor miRNA expression in the cell.Notably,we demonstrate for the first time that human innate lymphoid cells(ILCs)express miR-155.We further demonstrate a clear distinction between the sexes,with a significant increase in the number of ILCs expressing miR-155 in female-derived cells compared with male-derived cells upon in vitro stimulation.