INTRODUCTION
In recent decades, there has been a significant reduction in mortality
associated with premature birth, allowing for a greater number of
survivors of extremely preterm birth1.
Bronchopulmonary dysplasia (BPD; defined as a need for oxygen at or
beyond 28 days of life, and characterized in severity by degree of
support required at 36 weeks post-menstrual age)2 is a
common comorbidity in preterm neonates, associated with long-term
effects on respiratory function3,4. As the survival of
extremely preterm children increases, there is a need to evaluate the
outcomes of these children in all aspects of life and health, and how
different clinical and behavioural factors might mitigate morbidity.
Participation in physical activity can impact the health and well-being
of school-aged children5, and engagement in physical
activity in childhood increases the likelihood of ongoing physical
activity in adulthood6. Evaluating and encouraging
physical activity in preterm born children and youth is therefore
important for improving long-term health outcomes.
Prior studies on the physical activity of children with BPD have
demonstrated lower participation in physical activity through
self-report5,7,8. Study findings have been mixed,
showing both normal and reduced exercise tolerance9,10and similar aerobic capacity7 in children born preterm
(with and without BPD) when compared to children born at term. Children
with BPD have been shown to have pulmonary function abnormalities
including reduced forced expiratory volume in one second
(FEV1)7,8,11 and mid-expiratory flows
(FEF25-75)8, moderate-to-severe
airflow obstruction and hyperinflation9,11. They may
also have an increased respiratory rate11, lower tidal
volumes11, and decreased peak oxygen
saturation9,11 during aerobic activity, compared to
their full term peers without BPD. Furthermore, most adolescents and
young adults who had BPD in infancy have some degree of pulmonary
dysfunction (airway obstruction, hyper-reactivity, hyperinflation), even
if they were clinically asymptomatic12. Given these
findings of reduced lung function and exercise capacity in children with
BPD, it is important to understand physical activity in this population
and its relationship to measures of lung disease.
To date, studies evaluating degree of participation in physical activity
have been through self-report assessment tools, rather than by objective
means. There may be important differences between perceived and actual
participation in physical activity in this population, and physical
activity may be mitigated by other clinical or behavioural factors. This
study therefore sought to compare perceived exercise tolerance and
objective physical activity data in a home environment in children born
extremely preterm (<28 weeks gestation), who are now
school-aged (7-9 years), with and without history of BPD. We also
examined associations of physical activity with pulmonary magnetic
resonance imaging (MRI) and lung function. Our hypothesis was that
children with a history of BPD would have decreased physical activity
compared to those without a history of BPD.