U.S. researchers have found a link between exposure to violence in childhood with aggravated asthma in later life.

The study involved 397 adults with moderate to severe asthma who lived in an inner-city community. Nearly one-quarter of the participants had previously been exposed to violence.

The participants were followed for six months by researchers at University of Pennsylvania School of Medicine.

The findings showed that people who had been exposed to violence previously had nearly twice the rate of subsequent hospitalizations or emergency department visits for asthma as those who hadn't been exposed to violence.

The researchers come to the conclusion that people with asthma who had witnessed violence in their neighborhoods are at increased risk for asthma-related hospitalization and emergency department visits for asthma or any cause.

The study also found that exposure to violence was associated with lower asthma-related quality of life, and that younger adults were more likely to be exposed to violence and more likely to have had an emergency care visit in general.

It's not clear how exposure to violence affects asthma, but the researchers suggested that it may be a marker for physical or social conditions that contribute to the development of asthma, exacerbate symptoms, and interfere with successful treatment and management of the disease.

These conditions may include air pollution, inadequate housing and limited access to pharmacies.

It's also possible that the stress of living in a poor, violence-affected community directly affects the health of people with asthma, the researchers said, adding that the two theories were not mutually exclusive.

"Because overall ED (emergency department) visits increased and there was a trend toward increase in overall hospitalizations, our findings suggest that exposure to violence is associated with far reaching health effects beyond the single condition of asthma," said lead author Dr. Andrea J. Apter, a professor of medicine and chief of the allergy and immunology sections in the division of pulmonary, allergy and critical care medicine.

The study appears in the September issue of the Journal of Allergy &Clinical Immunology.