PROLONGED RECOVERY FROM EXERCISE-INDUCED ASTHMA WITH INCREASING AGE IN CHILDHOOD

It has been suggested that children with asthma recover more quickly f rom exercise-induced bronchoconstriction than adults. On the basis of clinical observation we hypothesized that recovery rate from exercise- induced asthma (EIA) in childhood also decreases with age. In 14 child ren (aged 7-12 years) with a history of EIA, we measured spontaneous r ecovery from bronchoconstriction induced by two different stimuli: exe rcise and histamine. The children visited the laboratory three times. After a screening exercise test on the first visit, standardized bronc hoprovocation tests with either exercise or histamine were performed o n the following two visits in random order. The degree of bronchoconst riction induced by histamine was matched for that observed after exerc ise. During recovery, forced expiratory volume in 1 second (FEV(1)) wa s measured repeatedly up to 2 hours postchallenge. The recovery rate ( % increase in FEV(1)/min) was calculated from the linear slope of the time-response curve. Differences in recovery rate between the two stim uli were analyzed by paired t-test, and age-related differences were a nalyzed using multiple regression analysis. For the group as a whole, recovery rate was not different between the two stimuli (mean +/- SD: 1.22 +/- 0.91 for exercise, and 1.46 +/- 0.65, for histamine, P = 0.31 ). However, the recovery rate for exercise-induced bronchoconstriction decreased significantly with age (r = -0.74, P = 0.003), in contrast to the recovery rate for histamine (r = -0.15, P = 0.60). Consequently , in the oldest age group (11-12 years, n = 5) recovery rate from exer cise challenge was significantly slower than in the younger age group (7-10 years, n = 9), i.e., 0.54 +/- 0.17 and 1.60 +/- 0.93, respective ly, P = 0.009, and slower than the recovery rate from histamine challe nge: 0.54 +/- 0.17 and 1.33 +/- 0.54, respectively, P = 0.03. In the y ounger age group the recovery rates from exercise and histamine were n ot different (1.60 +/- 0.93 and 1.54 +/- 0.73, respectively, P = 0.83) . We conclude that recovery from EIA in childhood decreases with incre asing age. These data suggest that the mechanism of exercise-induced a sthma in childhood changes with age. This might be due to changes in m ediator production or response to mediator release. (C) 1995 Wiley-Lis s, Inc.