The rate of asthma among children has tripled in the past few decades, and some researchers believe that smoking could be the cause, Science Daily reported May 22.

Researchers from Columbia University's Mailman School of Public Health noted that the increase in asthma cases has occurred primarily in industrialized nations, but now appears to be spreading to the developing world, as well.

"We have identified parallel increases in childhood asthma and cigarette use among adults during the past century in the United States. These parallel trends suggest that the increase in cigarette use may be a contributing factor to the rise in asthma among children during the same period through increased exposure to environmental tobacco smoke," said study author Renee D. Goodwin, Ph.D. MPH.

Goodwin noted that the risk of asthma was 2.5 times greater among children whose mothers smoked 10 or more cigarettes daily, compared to children of lighter smokers or those whose mothers did not smoke at all. The U.S. Department of Health and Human Services estimated that exposure to environmental tobacco smoke raises the risk of childhood asthma by 63 percent.

"Previous data that show more recent higher rates of cigarette smoking among lower socioeconomic status segments of the population within the United States are consistent with our theory, since these are the most vulnerable segments of the population among whom rates of childhood asthma are currently the most concentrated," wrote Goodwin. "Although cigarette consumption has declined in some segments of the United States population since its peak around 1981, the consequences and health effects of the drastic increase in the mid-1980s are still affecting adults and children."

The study was published in the May 2007 issue of the Annals of Allergy, Asthma & Immunology.