Autumn-born babies linked to asthma

Children born four months before the height of cold and flu season have a greater risk of developing childhood asthma than children born at any other time of year, new research has indicated.

The US study analysed the birth and medical records of more than 95,000 children and their mothers to determine whether being born at a certain time posed a higher risk for developing early childhood asthma.

The researchers found that autumn babies carried the greatest risk of having clinically significant bronchiolitis, which is associated with an increased risk of childhood asthma.

The age of a baby at the winter virus peak independently predicts asthma development, with the highest risk being for infants born about four months prior to the peak, according to Prof Tina V Hartert of Vanderbilt University, Tennessee. In the northern hemisphere, this is represented by the autumn months, she added.

“Birth during this time conferred a nearly 30% increase in odds of developing asthma,” she said.

The researchers have suggested two possible reasons for the link. Firstly, that there is a genetic susceptibility common to both bronchiolitis and the development of asthma, and secondly, that an environmental exposure such as winter viral infection causes asthma.

“The risk of progressing from bronchiolitis to asthma is almost certainly influenced by genetic factors. However, if this association were due only to genetic factors, there would be a seasonal effect on infection but not on asthma,” said Prof Hartert.

Unfortunately, predicting the peak of winter virus season is difficult – it can vary by up to ten weeks per year. The researchers note that avoiding winter virus would be nearly impossible, with 70% of infants becoming infected in their first year. However, for families whose infants are at high risk of developing asthma, there are a number of ways to reduce the risks, including avoiding infection through vaccination, or timing the birth to occur during the spring.

According to the researchers, while these strategies may hold the hope for reducing asthma prevalence, they first need to be studied.

It is estimated that about 470,000 people in Ireland have asthma. This equates to about one adult in 10 and one in five children. Research suggests that asthma is a growing problem. Chronic asthma is the most common long-term disease in children. It is the most common cause of lost days at school and the most common reason for a visit to the doctor.

For more on asthma, visit our asthma clinic at http://www.irishhealth.com/clin/asthma/index.html.

The research was published the American Journal of Respiratory and Critical Care Medicine.

[Posted: Fri 21/11/2008]