Tuesday, 16 September 2014

Damp and Mould are a Health Risk to Asthma Sufferers: A Review

There have been a series of research papers published over several years on the subject of whether damp living conditions are correlated with asthma. Some papers seem to support the claim, others do not. This most recent publication, a review from 3 labs in the UK looks at all of those papers and searches for threads of evidence running through all of them. Because this approach looks at all research taken together its conclusions are stronger than each paper looked at on its own.

Earlier papers, including the 2009 review article from the World Health Organisation have described damp as 'strongly associated' with some respiratory illnesses including exacerbation of asthma but found no strong evidence to suggest that mould itself was associated.

The findings of this new review seem to suggest more strongly that there is a link between moulds and asthma. They looked at the populations of moulds found in homes prior to the development of asthma and prior to exacerbation

Quoting from the paper:
Conclusion: Longitudinal studies assessing increased exposure
to indoor fungi before the development of asthma symptoms
suggests that Penicillium, Aspergillus, and Cladosporium species
pose a respiratory health risk in susceptible populations.
Increased exacerbation of current asthma symptoms in children
and adults were associated with increased levels of Penicillium,
Aspergillus, Cladosporium, and Alternaria species, although
further work should consider the role of fungal diversity and
increased exposure to other fungal species.
The conclusions are thus fairly strong in favour of the presence of particular moulds themselves being associated with asthma and increased asthma. This is not the same as saying that they are the cause of the asthma but this is another step in that direction. Of course it still could be that the presence of these moulds tells us that something else - the true cause - is present (e.g. the presence of mould indicates high humidity, high humidity also causes several other things to happen, one of which might cause asthma). It might also be telling us that mould spores might be a cause, as might vapours produced by moulds as both are deeply inhaled.

The authors suggest further work should identify more genus' & specific species of mould that correlate with asthma so as to get a more complete picture of what is going on in this complex scenario. Newer technologies designed to identify many hundreds of specific species based on polymerase chain reaction (PCR) are capable of doing this so they may well form the basis of future experiments. Exposure to moulds may occur more than once and this may be improtant for the development of asthma, consequently future experiments need to be designed with this in mind.

1 comment:

Ian Cull said...

Great summary post of a summary paper. Nice reminder that association is not necessary causation. I wonder if dampness and mold are a proxy for a poorly maintained property that has other issues going on.

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