Season of Birth May Affect Asthma

(November 23, 2008) - It is said that timing is everything, and that certainly appears to be true for autumn infants. Children who are born four months before the height of cold and flu season ((Read about "The Common Cold" "Influenza") have a greater risk of developing childhood asthma (Read about "Asthma") than children born at any other time of year, according to new research.

The study analyzed the birth and medical records of more than 95,000 children and their mothers to determine whether date of birth in relationship to the peak in winter respiratory viruses posed a higher risk for developing early childhood asthma. They found that while having clinically significant bronchiolitis (Read about "Bronchiolitis") at any age during infancy was associated with an increased risk of childhood asthma, for autumn babies, that risk was the greatest.

"Infant age at the winter virus peak following birth independently predicts asthma development, with the highest risk being for infants born approximately four months prior to the peak, which is represented by birth in the fall months in the Northern hemisphere. Birth during this time conferred a nearly 30 percent increase in odds of developing asthma," said Tina V. Hartert, M.D., M.P.H., principal investigator of the study.

The research was published in the American Journal of Respiratory and Critical Care Medicine, a publication of the American Thoracic Society.

The study demonstrated for the first time that timing of birth in relationship to the peak in winter virus activity independently predicts asthma development.

The researchers propose two non-mutually exclusive possible reasons for the link: One, that there is a genetic susceptibility common to both bronchiolitis and the development of asthma; and two, that an environmental exposure such as winter viral infection causes asthma.