Seasons Influence Exercise Test Results

Timing is important when diagnosing asthma.Researchers found that individuals who participatein exercise tests to help diagnose asthmamay get varying results, depending on the seasonof the year the test is conducted, accordingto a study reported in Chest (October 2005). Forexample, tests done in the summer, when asthmaflare-ups are generally less, appeared lesslikely to confirm asthma, compared with testsperformed in other seasons.

Although previous studies had indicated anassociation between exercise test results andseasons, those studies were all conducted outdoors.Cold temperatures and other environmentalfactors may have influenced the higherincidences of positive test results in the winter,the researchers noted. The recent study tookplace indoors, using treadmills in a laboratorythat was under constant temperature andhumidity.

For the study, 532 potential military recruits(17 years old) participated in exercise tests forsuspected asthma. The study results showedthat 26% of the participants tested positive forasthma after exercising, as measured by a≥10% drop in lung function. Positive testresults in the summer months from Julythrough September were seen in 13% of thepatients, compared with 29% to 31% duringthe rest of the year.