(The New York Times News Service) -- As an epidemic of asthma left more and more children wheezing during the past two decades, scientists blamed everything from obesity to cockroach droppings to the way we build our houses.

Now, researchers from Brigham and Women's Hospital have identified another potential cause: child abuse.

The Brigham doctors discovered that children in Puerto Rico who endure physical or sexual abuse are twice as likely to suffer from asthma as youngsters who do not face maltreatment. Abuse, the researchers found, was a more powerful predictor of whether a child would develop asthma than if a family was rich or poor.

Stress has recently been implicated as a trigger for asthma. And the Boston researchers said they believe that the extreme strain caused by abuse -- and the hormonal changes that result -- may predispose children to worse bouts of the disease, which ignites chest-rattling coughs and chronic shortness of breath. It is believed to be the first time researchers have established a possible link between child abuse and asthma.

"It certainly seems biologically plausible, particularly considering that it's hard to think of any more stressful circumstance for a child than physical or sexual abuse, especially when that abuse comes from within the family," said Dr. John Heffner, a past president of the American Thoracic Society who was not involved with the research but is familiar with it.

The Brigham scientists, who collaborated with specialists from Columbia University and the University of Puerto Rico, focused on Puerto Rican children because they are more likely to have asthma and to die from the disease than any other US youngsters, regardless of whether they live on the island or the mainland.

Roughly 25 percent of Puerto Rican children are diagnosed with asthma at some point during childhood, compared with 13 percent of white, non-Hispanic children and 16 percent of black youngsters.

"The question is, why?" asked Dr. Juan Celed?n, a lung specialist in the Brigham's Channing Laboratory. "Is this heredity? Is this environmental factors? Is this some behavioral or lifestyle factor?"

The researchers questioned about 1,200 children and their parents. Before they agreed to participate in the study, families were told that some questions would pertain to abuse and that authorities would be alerted if a child reported having been struck violently or subjected to sexual abuse.

Asthma was significantly more common among children who said they had faced abuse in the previous year, with 20 percent suffering from the respiratory ailment. Among children who had not sustained abuse, the asthma rate was 11.5 percent.

Still, abused children represented only a small fraction of the total number with asthma.

"It's very clear it's a very complex disease," Celed?n said.

"By no means should we say abuse is responsible for a majority of the cases. And I don't want this to stigmatize Puerto Ricans or other parents who have children with asthma."

From previous studies, the researchers knew that people who suffer abuse have depleted supplies of a pivotal hormone called cortisol that is regulated by the brain. That's relevant to asthma because cortisol helps reduce inflammation, and asthma causes airways to become furiously inflamed.

"We're not surprised that when we're frightened, our heart rate goes up," Heffner said. "So we shouldn't be surprised when organs, like the lungs, fail or malfunction through acute or long-term stress in the brain."

The study, Celed?n said, was not designed to definitively answer this crucial question: Was abuse actually triggering asthma? Conversely, it's possible children were more likely to be abused because they had asthma, making them more vulnerable. And the study's conclusions can't necessarily be extrapolated to all youngsters.

Still, Celed?n and Heffner said the findings are sufficiently concerning that doctors should take heed of them. When treating a child who has been abused, physicians should screen for asthma. And when a child has recurrent, persistent, hard-to-treat asthma, Heffner said, doctors should consider looking for evidence of abuse.

"This is basically saying stress, violence, events that are very traumatic may worsen asthma," Celed?n said, "and we should continue looking for it."

Copyright 2008 The New York Times News Service. All rights reserved.