The domestic environment has long been known to affect respiratory health. Many studies now attest to the effects of dampness and mould on pre-existing asthma including large international collaborations that incorporate New Zealand. These associations were confirmed in a detailed Institute of Medicine report in 2004. The same report suggested that the evidence that damp and mould were associated with the development of asthma were less clear. Since then a small number of studies has supported this association. In New Zealand there are high rates of asthma prevalence and morbidity and high rates of poor quality housing. The domestic environment may be an important driver of asthma development and one that is eminently treatable. However, it is not clear what aspects of the home environment make asthma worse or lead to the development of asthma
Participants, Aim and Design
This population based incident case control study is designed to answer two questions: is new onset wheezing in early childhood associated with the home environment and if so what mechanisms might be important. We aim to recruit 150 newly wheeze diagnosed children (aged 1-6 years) at the point of first treatment and compare their domestic environment with 300 matched children (matched for age, gender and area of domicile) who do not have wheezing. The study is progressing extremely well with recruitment expected to be completed by April 2012 and all 450 families interviewed and had their homes assessed by August 2012. Parents of children are being interviewed at home and a detailed self assessment of the home is recorded. Details of a variety of covariates are collected including family size, pets, smoking history and day care attendance. Children are skin prick tested to determine their atopic status. Because of the risk of recall bias and over reporting of home dampness where a child has been newly diagnosed with wheezing a detailed independent building report will be obtained for each home by a specially trained building assessor (blind to the case or control status of the home). A specific quantitative collection tool has been developed from our own Healthy Housing Index and from the quantitative assessments used for similar studies in Finland.
Objective measures are collected in the form of settled dust using dust fall collectors with electrostatic cloths and vacuum samples of floor and mattress dust. Dust will be analysed for house dust mite allergen, bacterial endotoxin (from Gram negative bacteria) and fungal beta glucans. All three of these measures have been associated both with the development and maintenance of asthma and with damp environments. In addition we will undertake quantitative PCR on the settled dust samples to assess the range and quantity of airborne fungi in each home. These measures are designed to evaluate possible mechanisms for any differences that we may observe between homes of cases and controls.
The study team brings together some of the most experienced researchers in this field including Professor Julian Crane, the study director; Jeroen Douwes of Massey University who was one of the members of the expert panel on the Institute of Medicine report and has extensive experience in this area; and Professors Pekkanen and Nevalainen from Finland who have pioneered studies of the effects of mould on human health, including case control studies of asthma development.
The reasons for the high rates of asthma in New Zealand are unknown, yet they represent a major cause of morbidity and health care expenditure. This study may establish one important cause of these high rates and offer explanations for the underlying mechanisms for asthma development. If so, interventions to improve the New Zealand domestic environment could have far reaching beneficial health consequences
The study is supported by the Health Research Council.