Health of Occupants of Mouldy Environments (HOME)
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Background
The domestic environment has long been known to affect respiratory health. Many studies now attest to the effects of damp and fungi on pre-existing asthma including large international collaborations that include 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 have supported this association. In New Zealand there are high rates of asthma prevalence and morbidity and high rates of damp and fungi in homes. The domestic environment in New Zealand may be an important driver of asthma development and one that is eminently treatable. However, it is not clear what aspects of damp mouldy environments make asthma worse or lead to the development of asthma.
Subjects, Aim and Design
The population based incident case control study proposed here is designed to answer two questions – “Is new onset asthma in early childhood associated with damp and mould and if so what mechanisms might be important.” We will recruit 150 newly diagnosed asthmatic children (aged 1-5 years) at the point of diagnosis and first treatment and compare their domestic environment with 300 matched children (matched for age, ethnicity and area of domicile) who do not have asthma. Parents of children will be interviewed at home and a detailed self assessment of the home will be recorded. Details of a variety of covariates will be collected including family size, pets smoking history and day care attendance. Children and their parents will be skin prick tested to determine their atopic status. Because of the risk of recall bias and over reporting of damp and mould in homes where a child has been newly diagnosed with asthma a detailed independent building report will be obtained for each home by a specially trained building inspector (blind to the case or control status of the home) The building report will focus on quantifying the extent of the damp and mould throughout the home. A specific quantitative collection tool will be developed from our own Healthy Housing Index and from the quantitative assessments used for similar studies in Finland. This will quantify mould and damp areas in the home based on the area of the largest patch.
Objective measures will also be collected in the form of settled dust using dust fall collectors with electrostatic cloths. Dust will be analysed for house dust mite allergen, bacterial endototoxin (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 settled dust samples will be collected from each home (using electrostatic cloths) as a surrogate for air sampling. In addition we will undertake quantatative 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 arguably some of the most experienced researchers in this field. Members of the Housing and Health programme with extensive experience of studies of housing and respiratory health over the last decade, Jeroen Douwes at 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.
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The study is supported by the Health Research Council.