"While we cannot definitively explain why some individuals experience asthma relapse and others do not, we found that persistence of asthma and asthma relapse are significantly increased in children with house dust mite sensitivity," said study author, Malcolm R. Sears, MB, ChB, FRCPC, McMaster University, Hamilton, Ontario, Canada. "This is likely due to persistent inflammation and genetic factors."
In a longitudinal, population-based, cohort study of 1,037 children born in New Zealand between 1972 and 1973, researchers from Dunedin, New Zealand, and Hamilton, ON, Canada, looked at factors that influenced the reoccurrence of asthma by early adulthood. Study participants were given respiratory questionnaires and spirometry testing at ages 9, 11, 13, 15, 18, 21, and 26, as well as additional lung function and allergen skin-prick testing at select ages. Of 868 patients evaluated at age 18, 176 (20.3 percent) had physician-diagnosed asthma during childhood, and, of those, 68 (38.6 percent) no longer experienced any asthma symptoms (measured by self-reported wheezing). During an eight-year follow-up period, researchers found that 24 of the 68 study participants (35 percent) who had previously gone into remission, relapsed by age 26. Although not statistically significant, the patients who relapsed more often had allergies to house dust mites, grass, cats, dogs, and mold; poorer lung function (measured by FEV1/FVC ratios at age 18); and increased frequency of responsiveness to methacholine or bronchodilator at age 21.
"I think that if our patient database was larger or if the study period was longer, our findings that atopy and poor lung function predict the likelihood of relapse in the future would prove to be true at statistically significant levels," said Dr. Sears. "By not smoking and avoiding occupations that increase the likelihood of developing asthma, patients can help protect themselves from asthma relapse."
The study also found that children who were more sensitive to house dust mites and cat allergens and/or had poor lung function were significantly less likely to experience asthma remission by the time they were age 18. Of those in remission at age 18, the poorer their lung function, the more likely they were to relapse. For those who relapsed by age 21 or 26, their asthma was generally milder than patients who had persistent asthma throughout their childhood and into adulthood. Nine percent of those without prior asthma or wheezing by the age of 18 developed adult asthma by the time they were 26 years of age.
"This study demonstrates the role that specific risk factors have on asthma remission," said Paul A. Kvale, MD, FCCP, President of the American College of Chest Physicians. "As specialists who see these patients regularly, we must develop management programs to reduce the likelihood of relapse."
CHEST is a peer-reviewed journal published by the ACCP. It is available online each month at www.chestjournal.org. ACCP represents 16,000 members who provide clinical respiratory, sleep, critical care, and cardiothoracic patient care in the United States and throughout the world. The ACCP's mission is to promote the prevention and treatment of diseases of the chest through leadership, education, research, and communication. For more information about the ACCP, please visit the ACCP Web site atwww.chestnet.org.