Introduction
Long-term pulmonary outcome in preterm infants usually involve chronic
respiratory impairment such as airway obstruction(1)and low diffusion capacity(2). Perinatal inflammation,
fetal growth restriction, bronchopulmonary dysplasia (BPD) and gender
are risk factors affecting the immature lung during the first years of
life(3-5). There is evidence that persistence of
respiratory symptoms, lung function impairment and abnormalities of the
lung structure may persist into adulthood(6, 7).
Infants with BPD have low respiratory compliance in the first month of
life, but with some normalization at 2 years of
age(8). Up to 8 years of age, there is still a
reduction of forced flows and volumes in these
children(4, 9). In an 11-year follow-up of extremely
preterm infants, the children had reduced forced expiratory volume in 1
second (FEV1) and forced expiratory flow between 25-75%
(FEF25-75) compared to term born
classmates(10). It has been suggested that the
observed increase in airway obstruction could be an expression of early
impaired airway development during childhood, whereas there seem to be
some catch-up through early life(7, 11). Furthermore,
small airway abnormalities, could be a risk for future chronic lung
disease and further decrease the respiratory outcome after preterm
birth(12), since prematurity per se is also a
well-known risk factor. A reduced lung function already at childhood,
may lead to a lower lung function throughout life(13).
Since BPD is a poor predictor of prematurity-associated lung
disease(11), and the respiratory outcomes after
preterm birth seem to be more dependent on the prematurity per se, it is
important to investigate preterm-born children also beyond
BPD.(14)
The primary aim of the study was to extensively investigate lung
function pattern at 12 years of age in children born very preterm, with
or without BPD during infancy as compared to term born controls. The
secondary aim was to study how different neonatal comorbidities and sex
may affect lung function and prevalence of airway symptoms during
childhood in preterm children.