NEW YORK (Reuters Health) - Smoking during pregnancy, daycare attendance and breastfeeding might be some of the main factors people can change to affect whether their infants develop wheezing, an international study suggests.
In a study of close to 29,000 children in two European and four Latin American countries, researchers found that in general, certain factors were consistently linked with the risk of infant wheezing.
Overall, babies who'd had a cold in the first three months of life were roughly three times more likely than other infants to develop recurrent bouts of wheezing before their first birthday. There was a similar risk linked to having been in daycare during the first year of life.
Another key factor seen in both Europe and Latin America was smoking during pregnancy, which was tied to a 44- to 48-percent increase in the risk of recurrent wheezing.
On the other hand, breastfeeding for more than three months was linked to decreased odds of recurrent wheezing across countries: overall, babies breastfed that long were about 20 percent less likely to have recurrent wheezing than those who were breastfed for shorter periods or not at all.
Wheezing refers to a high-pitched whistling sound, most obvious during exhalation, that is usually caused by blockages in the small breathing tubes in the chest.
Occasional wheezing is common in infancy, with an estimated 40 percent of children having at least one bout before age of 3. Wheezing in young children is often related to viral infections, and usually does not mean that a child will eventually be diagnosed with asthma.
But young children with recurrent wheezing -- defined as three or more episodes in a year -- over time are relatively more likely to develop asthma, particularly if they have risk factors such as family history of allergies and asthma.
The new study, published in the journal Pediatric Allergy and Immunology, looked only at wheezing episodes in the first year of life, and not longer term asthma risk.
The findings support what a number of previous studies have shown, lead researcher Dr. Luis Garcia-Marcos, of the University of Murcia in Spain, told Reuters Health in an email.
Early daycare attendance, he noted, may boost the risk of infant wheezing by exposing babies to more viruses, whereas breastfeeding may help prevent such infections -- and, therefore, viral-related wheezing.
But as far as long-term asthma risk, Garcia-Marcos pointed out that some studies have linked early daycare to a lower risk -- in theory, precisely because infants in daycare tend to get more infections. That may affect immune-system development in a way that makes asthma less likely later in life.
What's new in the current study, Garcia-Marcos said, is that it included less-affluent countries -- namely, Chile, Columbia, Brazil and Venezuela -- and two wealthier European nations, Spain and the Netherlands. For the most part, the same factors -- early daycare, early-life colds, breastfeeding and smoking during pregnancy -- showed similarly strong links to wheezing risk in both the Latin American and European nations.
The rate of those risk factors did vary among nations, however.
For example, across the two European countries, nearly one-quarter of infants attended daycare in the first year of life, versus 13 percent of those in Latin American countries. So on the public-health level, early daycare may be a more important factor in European countries, the researchers note.
Perhaps the best thing mothers can do to lower the risk of infant wheezing, Garcia-Marcos said, is to avoid smoking during pregnancy. That would also help avert the many other hazards linked to prenatal smoking, including premature birth, low birth weight and an increased risk of sudden infant death syndrome.
He also recommended breastfeeding as a potential way to lower rates of early-life infections. In general, experts encourage exclusive breastfeeding for an infant's first six months of life.
SOURCE: http://www3.interscience.wiley.com/journal/123391801/abstract Pediatric Allergy and Immunology, online April 27, 2010.