Asthma seems to affect more than the lungs. (Gary Kazanjian/Associated Press)

People with asthma may be more likely to suffer from other diseases that require medical care, according to a new study.

The research, released Tuesday by Toronto's Institute for Clinical Evaluative Sciences, looked at comorbidity — diseases that accompany another disease, in this case asthma — based on a review of health care claims by Ontario's 12 million residents in 2005.

"What we were able to empirically demonstrate was that there is clearly more to having asthma than just having lung disease," said the study's lead author Dr. Andrea Gershon, an ICES scientist, respirologist and researcher at Sunnybrook Health Sciences Centre.

Other respiratory disease, psychiatric disease, and musculoskeletal disease were the most common types of comorbidity found in those with asthma.

In the study, asthma and asthma comorbidity were associated with:

• six per cent of the 2.2 million hospitalizations.
• nine per cent of the 4.7 million emergency room visits.
• six per cent of the 131.3 million ambulatory care visits or outpatient trips to doctors in Ontario.

For example, the number of emergency department visits among asthmatics for non-asthma medical claims was 68 per 100 individuals compared with nearly 33 per 100 among those without asthma, the researchers found.

Asthma is most common in children and young adults who are generally assumed to be a healthy population.

Goal is better care

"We hope our findings will help health-care providers realize that it is likely that their own asthma patients suffer from asthma comorbidity, and prompt them to look for and manage it appropriately in order to improve overall care," Gershon said.

The cause-and-effect relationships are unclear, the researchers said. Factors could include whether poor asthma control or asthma treatment are linked with the other diseases, whether other diseases cause asthma, where something else causes both, or if some combination is at play.

But if researchers find out more about how asthma affects the body beyond the lungs, then it might help in the search for better ways to treat it, help people to feel better and use fewer health-care resources, Gershon said.

The study was done in Ontario but Gershon believes the findings would apply to similar populations elsewhere including in other provinces.

The study appears in Tuesday's issue of the journal Thorax.

According to the World Health Organization, Canada has one of the highest prevalence rates of clinical asthma in the world — about 14 per cent — but one of the lowest fatality rates from the disease, at 1.6 deaths per 100,000 asthmatics.

The research was funded by the Canadian Institutes of Health Research, the Government of Ontario and the Public Health Agency of Canada.