Timing is important when diagnosing asthma. Researchers found that individuals who participate in exercise tests to help diagnose asthma may get varying results, depending on the season of the year the test is conducted, according to a study reported in Chest (October 2005). For example, tests done in the summer, when asthma flare-ups are generally less, appeared less likely to confirm asthma, compared with tests performed in other seasons.
Although previous studies had indicated an association between exercise test results and seasons, those studies were all conducted outdoors. Cold temperatures and other environmental factors may have influenced the higher incidences of positive test results in the winter, the researchers noted. The recent study took place indoors, using treadmills in a laboratory that was under constant temperature and humidity.
For the study, 532 potential military recruits (17 years old) participated in exercise tests for suspected asthma. The study results showed that 26% of the participants tested positive for asthma after exercising, as measured by a ≥10% drop in lung function. Positive test results in the summer months from July through September were seen in 13% of the patients, compared with 29% to 31% during the rest of the year.