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Infants and Antibiotics: Asthma Risk?

Research Suggests Link Between Antibiotic Use by Infants and Development of Asthma
WebMD Health News
Reviewed by Louise Chang, MD

June 11, 2007 -- Infants who receive antibiotics in their first year of life are more likely to develop asthma by age 7, and multiple courses of the drugs boost the risk more, a Canadian study suggests.

"In children receiving five or more courses of antibiotics in the first year, the risk of asthma was 1.5 times more likely than in children getting no antibiotics [during their first year]," study researcher Anita Kozyrskyj, PhD, tells WebMD. Kozyrskyj is associate professor of pharmacy and medicine at the University of Manitoba in Winnipeg, Canada.

The study was published in the June issue of the journal Chest.

"The link between antibiotics and asthma was seen in children born to mothers without asthma, who are considered at low risk," Kozyrskyj says. And the link held even after other risk factors were taken into account. However, the study shows having a dog in the household while the child is a baby confers a protective effect.

Asthma affects almost 5 million children under age 18 in the U.S., according to the American Academy of Allergy Asthma & Immunology, including 1.3 million children under age 5.

Antibiotics and Asthma Risk

The new research adds to an ongoing debate in recent years about the effect early antibiotics may have on a child's risk of developing asthma. Kozyrskyj says research results are mixed; some studies, like hers, show an association (but not necessarily cause and effect), while other studies do not.

A report released in 2006 that analyzed five different studies found that infants who got even one course of antibiotics during their first year may have double the risk of getting asthma later in childhood than babies who received no antibiotics for their first 12 months.

Kozyrskyj and her colleagues used a prescription database from the University of Manitoba and McGill University in Montreal to monitor the antibiotic use of 13,116 children from birth to age 7 years. They noted in particular the antibiotic use in the first year and whether the child had developed asthma by age 7.

When antibiotics were given, the reason was noted -- including lower respiratory tract infections (such as bronchitis), upper respiratory tract infections (such as ear infection), or nonrespiratory tract infection (such as urinary or skin infections). Researchers also noted each child's risk factors for getting asthma, such as having a mother with asthma.

Besides looking at the records, "we also sent out a one-page survey to ask additional questions," Kozyrskyj says. Researchers asked parents to note whether children were exposed to tobacco smoke as infants and whether the household included dogs or cats.

More Findings

Within the group, 6% of the children had asthma by age 7. Antibiotic use was widespread, with 65% of the children having been prescribed at least one course of the medication during the first year of life.

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