MEDICINE / SOLVING THE ASTHMA MYSTERY : Rise in Cases, Deaths May Be Linked to Microorganism
A team of researchers has stumbled upon what they and others say could be a partial explanation for the recent rise in asthma cases and deaths--a trend that epidemiologists have observed worldwide and have been at a loss to explain.
The researchers, studying respiratory illnesses caused by a recently identified germ, found that men and women infected with chlamydia pneumoniae were more likely than others to develop wheezing, asthmatic bronchitis and asthma after a bout of respiratory illness.
The findings, published today in the Journal of the American Medical Assn., are preliminary and must be confirmed. But researchers say they raise the possibility of perhaps preventing some asthma cases by controlling the microorganism with antibiotics.
“Considering there is an international increase in the incidence of asthma and in asthma death rates, this is an exciting observation,” said Dr. Roger Bone, of Rush Presbyterian-St. Luke’s Medical Center in Chicago, who wrote an editorial accompanying the study.
Chlamydia pneumoniae is a microorganism between the size of a bacterium and a virus. It is known to cause respiratory tract disease, including pharyngitis, bronchitis and pneumonia. While it is probably not new, it has only been identified within the past decade.
Studies of blood samples suggest the germ, or pathogen, is widespread: Some 30% to 50% of adults worldwide show evidence of exposure. Evidence of infection is relatively low among infants, higher among children and highest in adults over age 30.
In the study, researchers at the University of Wisconsin and Wisconsin State Laboratory of Hygiene examined cases of respiratory tract illness in 365 white men, women and children treated at four family-practice clinics in and near Madison, Wis.
The researchers found that 47% of the 19 patients with acute chlamydia pneumoniae infection had bronchospasm, the spasmodic contractions suffered by asthmatics. The higher the levels of antibody to the germ in the patients’ blood, the more likely they were to wheeze.
Similarly, infected patients were more likely than others to develop asthmatic bronchitis after a respiratory illness. Four infected patients had newly diagnosed asthma after illness; four others had a new bout of an old case of asthma.
“It certainly provides us with a possible clue (to a cause of asthma) and it makes sense,” said Rjurik Golubjatnikov, a co-author of the paper. “The most hopeful thing is that the organism can be treated. That offers some prospect for prevention of asthmatic conditions.”
Asthma is a chronic inflammatory disorder of the airways, causes of which are unknown, though it can be triggered by exposure to pollen, dust and other allergens. While deaths remain relatively rare, asthma may affect as much as 5% of the U.S. population.
Over the past decade, the asthma death rate appears to have risen in the United States. Similar trends have been reported in other industrialized countries. Researchers have also reported changes in patterns of hospitalization among children with asthma.
Some believe asthma incidence and deaths are genuinely on the rise. Others suggest reporting and documentation are simply better. Some trace the apparent rise to declining access to health care, exposure to pollutants and increased survival of infants with major respiratory problems.
In their study, the Wisconsin researchers speculated that infection with chlamydia pneumoniae perhaps causes damage to the lining of the airways, leading over time to the chronic airway inflammation seen in cases of asthma.
