There is "strong evidence" of an association between asthma and complications from a common bacterium known to cause pneumonia, researchers report in The New England Journal of Medicine.

Pneumococcal disease is an infection caused by the bacterium Streptococcus pneumoniae, also known as pneumococcus. The most common types of infection caused by this bacterium are ear infection, lung infection (pneumonia), blood stream infection (bacteremia), sinus infection, and meningitis.

Researchers say that people with high-risk asthma are three times as likely to get complications from this infection as those without asthma. People with low-risk asthma have double the risk of those without asthma, says the study.

The results didn't change when sex, race, long-term use of corticosteroids, and other high-risk coexisting conditions were considered.

"As the incidence of asthma continues to climb in the United States, the burden of invasive pneumococcal disease is likely to increase," say the researchers, who include Thomas Talbot, MD, MPH, of Vanderbilt University's medical school.

Asthma Rising Worldwide

Asthma is on the rise in the U.S. and many other developed countries, for reasons health experts don't totally understand.

Between 100 and 150 million people worldwide have asthma, says the World Health Organization (WHO). In the U.S., the number of people with asthma has grown by more than 60% since the early 1980s, says the WHO.

The Asthma and Allergy Foundation of America estimates that 20 million Americans (one in 15 people) have asthma, with rates rising across all age, sex, and racial groups.

Tracking Asthma and Pneumonia

Talbot's study included 635 people who developed complications from pneumococcus infection sometime between 1995 and 2002. The study also included 10 times as many people without the infection.

All participants were 2-49 years old and had been participants in Tennessee's Medicaid program for more than a year.

Some people in each group had asthma. Those with infection included many more people with asthma (114 people, or 18 percent). In comparison, only 8 percent of those without infection (516 people) had asthma.

That translates to 4.2 episodes of infection per 10,000 people with high-risk asthma, 2.3 episodes per 10,000 people with low-risk asthma, and 1.2 episodes of infection per 10,000 people without asthma.

High-Risk Asthma

The study defined "high-risk asthma" as asthma that required admission to a hospital or emergency department, long-term use of oral steroids used for asthma control, or the dispensing of three or more prescriptions for inhaled drugs called beta-agonists within the year before enrollment in the study.

"Asthma" was defined as one or more inpatient or emergency department diagnoses of asthma, two outpatient diagnoses, or the use of asthma medications.

Would Vaccination Help?

As asthma rises in the U.S., "discussions about the feasibility and cost-effectiveness of pneumococcal vaccination among persons with asthma will need to be carefully explored," write Talbot and colleagues.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Talbot, T. The New England Journal of Medicine, May 19, 2005; vol 352: pp 2082-2090. World Health Organization: "Bronchial Asthma." Asthma and Allergy Foundation of America: "Asthma Facts and Figures."