Background There is increasing interest in the role physical activity (PA) can play in the development and management of asthma. Understanding whether PA can have a positive effect is hindered by the potential influence of asthma on PA and a lack of relevant longitudinal data, leading to a debate on the existence and direction of these links. The aim of this study was to explore whether having asthma results in lower PA levels, and/or whether lower PA levels lead to more asthma in children and adolescents.

Methods In a population-based study of 4983 children, data on asthma and PA were collected via questionnaires and time use diaries biennially, between the ages of 6 and 14. Current asthma was defined as use of asthma medications or wheeze in the past year, and incident asthma was defined as doctor’s diagnosis since the previous wave. PA was time spent doing moderate-to-vigorous physical activities in a day. Bidirectionality of this relationship was investigated using cross-lagged structural equational models.

Results PA was not longitudinally associated with incident or current asthma. Similarly, there was no evidence that incident or current asthma predicted PA at any of the ages.

Conclusions Using a novel strategy to investigate bidirectionality between PA and asthma, our results suggest that asthma and PA participation are not longitudinally associated in either direction. Our findings suggest that PA does not play an important role in the development or persistence of asthma.