Low physical fitness in childhood is associated with the development of asthma in young adulthood: the Odense schoolchild study

Intense physical activity in children may either improve fitness and protec t against asthma, or may trigger symptoms. The aim of this study was to det ermine whether physical fitness in childhood has an impact on the developme nt of asthma. In this prospective, community-based study, 757 (84%) asymptomatic children with an average age at inclusion of 9.7 yrs were followed for 10.5 yrs. In both surveys a maximal progressive exercise test on a bicycle ergometer wa s used to measure physical fitness (maximal workload) and to induce airway narrowing. A methacholine provocation test was performed in the subjects at follow-up. During the 10-yr study period, 51 (6.7%) of the previously asymptomatic chi ldren developed asthma. These subjects had a lower mean physical fitness in 1985 than their peers: (3.63 versus 3.89 W.kg(-1); p=0.02) in boys and (3. 17 versus 3.33 W.kg(-1); p=0.02) in girls. A weak correlation was found bet ween physical fitness in childhood and airway responsiveness to methacholin e at follow-up when adjusted for body mass index, age and sex (r=0.11; p<0. 01); In a multiple regression analysis, physical fitness was inversely rela ted to the development of physician diagnosed asthma, odds ratio=0.93 (0.87 -0.99). Thus, the risk for the development of asthma during adolescence is reduced 7% by increasing the maximal workload 1 W.kg(-1). In conclusion, this study showed that physical fitness in childhood is weak ly correlated,vith the development of asthma during adolescence and that hi gh physical fitness seems to be associated with a reduced risk for the deve lopment of asthma.