Asthma: is it inherited?
A considerable amount of research is taking place around the world to try to answer this question. We already know that asthma does seem to run in families, but the genetic component appears to be only part of the answer.
Asthma genes
From genetic research that has already been done, doctors know that asthma is a ‘complex’ heritable condition. This means that a number of genes — not just one — contribute to our susceptibility towards a particular condition.
Our genes are located in the body on chromosomes, with each chromosome containing hundreds of genes. So far, several chromosomes have been implicated as being possible locations for specific asthma genes.
In 2002, scientists identified a gene that they believe plays a key role in the development of asthma. The gene, known as ADAM33, on chromosome 20 has been found to be related to the development of over-responsive airways (over-sensitive, ‘twitchy’ airways), which are characteristic of asthma.
Researchers from the University of Southampton in the UK, who helped discover the gene, say that it could account for about 40 per cent of asthma cases, and that it could lead to new ways of diagnosing and treating asthma.
An inherited condition?
It's clear that asthma tends to run in families. For example, if one or both of your parents have asthma, you have a higher-than-usual chance of being susceptible to asthma as well.
However, people with very severe asthma can have children who never develop the condition. So it seems that being genetically susceptible to developing asthma isn't the whole story.
Environment
Environmental factors are also significant in determining who develops asthma.
It seems likely that social and environmental factors, such as lifestyle (for example, whether we smoke or not), housing (for example, whether our homes are well-ventilated to minimise levels of dust mites or moulds), and indoor and outdoor pollution exposure, may interact with an inherited genetic factor to promote the development of asthma in susceptible people.
Allergy is a key cause of asthma in adults and children so exposure to things that trigger an allergic response in susceptible people (allergens), such as house dust mite — or, more precisely, its droppings — is important in influencing the development of asthma.
Other environmental factors that may also have an impact on the development of asthma include:
- the mother smoking while pregnant;
- exposure to cigarette smoke in childhood (passive smoking); and
- exposure to colds or viral infections.
Although many children with asthma seem to outgrow it when they reach puberty, once sensitive airways have been developed, they remain that way. So some of those people whose asthma symptoms decrease after puberty may find asthma symptoms reappearing in their late 30s or early 40s.
So even if your asthma is not active, it's a good idea to continue avoiding things that you know trigger your asthma, and to keep your asthma medications or prescriptions up-to-date in case you need them. If you're worried about your chances of asthma symptoms reappearing, talk to your doctor.
Last Reviewed: 04 March 2003
