14 December 2001 News Update
ASTHMA "IS MAINLY INHERITED'' - TWINS STUDY SHOWS
Findings just published suggest that asthma is chiefly an inherited genetic disease rather than one caused by environmental factors.
The results from a large-scale study of twins in England and Wales show that genes are "68 per cent responsible'' for asthma in young children. Shared environmental influences accounted for only 13 per cent of asthma prevalence and were not statistically significant.
New Zealand, Australia and the UK have the highest asthma rates in the world.
Although asthma can strike at any age, more than 80 per cent of asthmatics experience their first episode before the age of five.
The study conducted by doctors at the Institute of Psychiatry in London and the University of Southampton, southern England, is believed to be the first to have examined genetic influences on asthma pre-school children.
A survey was conducted among the parents of 4,910 four-year-old twins born in England and Wales between 1994 and '95. Parents were asked what treatment their children had been given for asthma and whether their children were identical or non-identical twins.
Identical twins share all their genes, whereas non-identical twins only share about half. A higher rate of asthma among identical twins would therefore indicate genetic factors at work.
The researchers, led by Dr Gesina Koeppen-Schomerus at the Institute of Psychiatry, King's College Hospital, found that identical twins had far more similar asthma histories than non-identical pairs.
Account was taken of shared and non-shared environmental factors such as family diet, air pollution, parental smoking, domestic pets and house-dust mites. Shared environmental factors only contributed to 13 per cent of asthma prevalence and non-shared environmental factors for 19 per cent. Genetic factors, on the other hand, accounted for 68 per cent.
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