A team of researchers led by Dr. Tina Hartert, director of the Center for Asthma Research and Environmental Health at Vanderbilt University, examined records for more than 95,000 children and their mothers in Tennessee.
They found that risk for childhood asthma was higher for babies who suffered from a respiratory tract infection early in life -- and babies born in the fall months seemed particularly at risk for contracting respiratory viral infections.
Risk was highest for infants born in early fall, approximately four months before the winter peak. The researchers' findings suggested that these babies, who are most likely those conceived in December or January, have a nearly 30 percent greater risk for developing asthma.
"Although it's difficult to influence birth timing, this study suggests that avoiding conceiving these months may have short and long-term benefits," Hartert explained. "Still, we must prove if preventing these respiratory tract infections will prevent a lifetime chronic disease."
Getting to the Roots of Asthma
The National Heart, Lung and Blood Institute estimates that more than 22 million people in the United States have asthma. Of this figure, nearly 6 million are children.
Though an array of treatments are available to help people live with asthma, in many cases the precise reasons for the development of the condition remain unclear.
Hartert's team suggests that the development of asthma in children could be tied to whether they have suffered a respiratory infection during their first year of life -- particularly since the children in question are born at a time when cold and flu rates are on the rise.
However, the researchers caution that this study does not prove that preventing a respiratory tract infection early in life will also prevent the development of asthma later on.
The other side of the equation is genetics, and doctors say the interplay between a child's natural susceptibility to the condition and the infections they sustain while young could decide their asthma fate.
"It's pretty convincing that [asthma is] due to the [respiratory] virus," said Dr. Elliot Israel, director of clinical research in the Pulmonary Division at Brigham and Women's Hospital in Boston, Mass. "The virus may be responsible for some asthma. If you have a strong family history of asthma, [you] may want to time your birth."
Hartert estimates that your risk for developing asthma is about 40 percent if one parent has asthma, and about 80 percent if both parents have asthma. However, she estimates that contracting a serious viral respiratory infection in early life can increase your chances of developing asthma by about 30 to 40 percent.
Dr. Franklin Adkinson, professor of medicine and associate training program director of the Johns Hopkins University Asthma and Allergy Center, said at the very least, the research could give new parents another reason to keep their babies cold- and flu-free.
"The interaction between a particular developmental period and seasonal environmental factors substantially [increase] the genetic predisposition for persistent asthma in young children," Adkinson said. "If the authors' hypothesis is correct, an effort to reduce viral infections by environmental controls or use of a vaccine could have a major impact on reducing asthma in children."
No Sex Till Spring?
So, could timing your child's birth -- and by extension, its conception -- lower his or her asthma risk? Some physicians said the idea was not out of the realm of possibility.
"Will we actually advise our future 'mommies' that have asthma when to conceive, as it may have a clinical impact on those families with high risk for asthma?" asked Dr. Clifford Bassett, medical director of Allergy and Asthma Care of New York.
However, most experts urged that making such a recommendation to asthma patients trying to conceive based on this study alone would be extremely unwise before more studies can confirm these findings.
"More confirmatory work, and the effect of an intervention to reduce viral infections during the first year of life will be required before recommendations for prevention can be made," Adkinson said.
After all, Adkinson reminded, the jury is still out on much asthma research. He pointed to a recent study published in the November 2007 issue of Journal of Allergy and Clinical Immunology, which found that children enrolled in daycare programs who were exposed to viral infections during their first year of life were more protected against the development of asthma.
"So it is important not to jump to conclusions based on this study alone," Adkinson added.
However, if future studies confirm the relationship between contracting a respiratory infection during the first year of life and the development of childhood asthma, Hartert believes it will be a significant step towards reducing asthma rates in the U.S.
"The role of the environment in the development of asthma is not as strong as genes, but we can't change our genes, and we can change things that are in the environment," Hartert explained. "Decreasing the severity or preventing these infections might prevent lifelong chronic disease."