Strachan D P, Aït-Khaled N, Foliaki S, Mallol J, Odhiambo J, Pearce N, Williams H C
Population Health Research Institute, St George's, University of London, Cranmer Terrace, London, UK.
Clin Exp Allergy. 2015 Jan;45(1):126-36. doi: 10.1111/cea.12349.
Associations of larger families with lower prevalences of hay fever, eczema and objective markers of allergic sensitization have been found fairly consistently in affluent countries, but little is known about these relationships in less affluent countries.
Questionnaire data for 210,200 children aged 6-7 years from 31 countries, and 337,226 children aged 13-14 years from 52 countries, were collected by Phase Three of the International Study of Asthma and Allergies in Childhood (ISAAC). Associations of disease symptoms and labels of asthma, rhinoconjunctivitis and eczema were analysed by numbers of total, older and younger siblings, using mixed (multi-level) logistic regression models to adjust for individual covariates and at the centre level for region, language and national affluence.
In both age groups, inverse trends (P < 0.0001) were observed for reported 'hay fever ever' and 'eczema ever' with increasing numbers of total siblings, and more specifically older siblings. These inverse associations were significantly (P < 0.005) stronger in more affluent countries. In contrast, symptoms of severe asthma and severe eczema were positively associated (P < 0.0001) with total sibship size in both age groups. These associations with disease severity were largely independent of position within the sibship and national GNI per capita.
These global findings on sibship size and childhood asthma, rhinoconjunctivitis and eczema suggest at least two distinct trends. Inverse associations with older siblings (observations which prompted the 'hygiene hypothesis' for allergic disease) are mainly a phenomenon of more affluent countries, whereas greater severity of symptoms in larger families is globally more widespread.
在富裕国家，较大的家庭规模与花粉症、湿疹及过敏致敏客观指标的较低患病率之间的关联已得到较为一致的发现，但在较不富裕的国家，人们对这些关系知之甚少。
通过儿童哮喘和过敏国际研究（ISAAC）第三阶段收集了来自31个国家的210,200名6至7岁儿童以及来自52个国家的337,226名13至14岁儿童的问卷数据。使用混合（多层次）逻辑回归模型，针对个体协变量以及地区、语言和国家富裕程度等中心层面因素进行调整，分析哮喘、鼻结膜炎和湿疹的疾病症状及诊断与同胞总数、年长同胞和年幼同胞数量之间的关联。
在两个年龄组中，报告的“曾患花粉症”和“曾患湿疹”均随同胞总数增加，尤其是年长同胞数量增加呈反向趋势（P < 0.0001）。在较富裕国家，这些反向关联更为显著（P < 0.005）。相比之下，两个年龄组中重度哮喘和重度湿疹症状均与同胞总数呈正相关（P < 0.0001）。这些与疾病严重程度的关联在很大程度上独立于在同胞关系中的位置以及国家人均国民总收入。
这些关于同胞数量与儿童哮喘、鼻结膜炎和湿疹的全球研究结果表明至少存在两种不同趋势。与年长同胞的反向关联（这些观察结果引发了关于过敏性疾病的“卫生假说”）主要是较富裕国家的现象，而大家庭中症状更严重在全球更为普遍。
