Asthmatics Have an Increased Risk for Heart Disease, Diabetes

Barbara Boughton

March 21, 2011

March 21, 2011 (San Francisco, California) — The first population-based study on asthma and associated proinflammatory conditions has revealed that asthmatics have double the risk for diabetes mellitus and a 50% higher risk for coronary artery disease than nonasthmatics, according to research presented here at the American Academy of Allergy, Asthma and Immunology 2011 Annual Meeting.

The study used the Rochester Epidemiological Project, a database maintained by the Mayo Clinic in Rochester, Minnesota, to study children and adults with asthma diagnosed and treated between 1964 and 1983 at the Mayo Clinic, and the incidence of heart disease, diabetes mellitus, rheumatoid arthritis, and inflammatory bowel disease.

Although many studies have investigated the cause of asthma, the impact of this chronic condition on other diseases is not well understood. Asthma increases proinflammatory cytokines such as interleukin-6, and might, therefore, play a role in the development of coronary artery disease, the researchers hypothesized. The proinflammatory cytokine T helper-17, which has been implicated in asthma progression, also plays a role in increasing the risk for rheumatoid arthritis and inflammatory bowel disease, said presenting author Hyun Don Yun, MD, from Harbor Hospital in Baltimore, Maryland, in an interview with Medscape Medical News.

In the Mayo Clinic study, the researchers found that asthma subjects also had an increased risk for rheumatoid arthritis and inflammatory bowel disease, although the difference in incidence did not reach statistical significance, Dr. Yun added.

The incidence of rheumatoid arthritis, inflammatory bowel disease, coronary artery disease, and diabetes among the Mayo Clinic patients was calculated using physician diagnoses and medical index codes, but the asthmatic subjects included in the study were selected using stringent criteria established by the researchers. "In our study, we worked to overcome selection bias by using predetermined clinical criteria for asthma, such as variability of symptoms and wheezing that was not continuous," Dr. Yun said.

"Our study has clinical implications for those who treat patients with asthma; follow-up care should address early detection of coronary artery disease and diabetes," said senior author Young Juhn, MD, associate professor of pediatric and adolescent medicine at the Mayo Clinic and director of pediatric asthma epidemiology research unit.

In the study, 2400 asthma patients from the Mayo Clinic were matched, in a 1:2 ratio, by age and sex with 4800 control subjects who did not develop asthma. Incidence rates of coronary artery disease, diabetes, rheumatoid arthritis, and inflammatory bowel disease were assessed.

Results revealed that the hazard ratio for diabetes mellitus and coronary artery disease among asthmatics was 2.12 and 1.46, respectively (P = .00002 and P = .027). Although results for rheumatoid arthritis and inflammatory bowel disease did not reach statistical significance, they showed a clear trend toward increased incidence among asthmatics. Results revealed that asthmatics had a hazard ratio of 1.4 for rheumatoid arthritis and 1.3 for inflammatory bowel disease.

The investigators acknowledged that there were several important limitations to the study, including its retrospective nature and the relatively small sample size for rheumatoid arthritis and inflammatory bowel disease, both much less common diseases than asthma. The study also did not adjust for possible confounders such as the use of oral steroids, associated obesity and high blood sugar among asthmatics, or the exercise habits of asthmatics who were more sedentary than control subjects, Drs. Yun and Juhn acknowledged.

"In future studies, we will be looking at case controls with coronary artery disease and asthma and analyzing confounding variables such as obesity," Dr. Juhn said. "But this study is an important start; it is our first look at the possible impact of asthma on other proinflammatory conditions," he said.

"This is an extremely interesting study because it used a very rigorous cohort that has been well characterized," said Andrew Liu, MD, associate professor and training program director in pediatric allergy and immunology at the National Jewish Medical and Research Center at the University of Colorado in Denver.

"It provides us with some insight into the immune dysregulation that may be at the heart of allergies and asthma, and helps us understand the nature of asthma and the susceptibility of these patients to other chronic diseases," he said.

Dr. Yun, Dr. Juhn, and Dr. Liu have disclosed no relevant financial relationships.

American Academy of Allergy, Asthma and Immunology (AAAAI) 2011 Annual Meeting: Abstract 293. Presented March 20, 2011.

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