RESULTS
There were 45 participants enrolled in this study, of which 28 met
criteria for BPD in infancy, and 17 did not. Among several differences
in the two groups of children, those with BPD had a lower gestational
age at delivery, lower average birth weight, a greater percentage of
males and lower height percentile at the time of evaluation (Table 1).
Of the 45 participants, 37 children had valid pedometer data and were
included in the pedometer analyses. Five children were excluded due to
insufficient days of recording, 2 children did not return their
pedometer, and 1 had their data accidentally deleted prior to upload. An
additional 4 participants of the 37 were missing data on MVPA due to
pedometer data uploading issues at a single site.
Comparing children with and without history of BPD, there were no clear
differences between the average number of daily steps, MVPA, or PAQ
score (Table 2). Of the 37 participants with valid step count data, 27
had also had reliable PFT and MRI data. A Spearman correlation matrix
was conducted to assess the correlation between daily step count, daily
MVPA, PAQ score, PFT measures, and MRI measures (Table 3). While PAQ
score was weakly correlated with both pedometer outcomes, there was a
very strong correlation between average daily step count and average
daily MVPA (r=0.90). A higher average daily step count was moderately
correlated with higher FVC % predicted, lower LCI, and greater proton
density at full expiration. A higher average daily MVPA was moderately
correlated with higher FVC % predicted, higher TLC % predicted, lower
LCI, and greater proton density at full expiration. All other pulmonary
function measure associations were weak or negligible.
A linear regression analysis demonstrated an association between FEV1 %
predicted and daily step count, after adjusting for MRI total proton
density and BPD status. MRI total proton density and BPD status were not
associated with average daily step count (Table 4a). A separate linear
regression analysis with average daily MVPA as the outcome found similar
results, with FEV1 % predicted marginally associated with average daily
MVPA, after adjusting for MRI total proton density and BPD status (Table
4b). Sensitivity analyses examining the impact of site found that while
it resulted in wider confidence intervals, the direction of association
between FEV1 % predicted and both pedometer outcomes remained the same.
Of the 45 participants, 42 had medication data available. Of the 42
participants with available medication data, 6 were taking ADHD
medications – 1 in the non-BPD group, and 5 in the BPD group. When we
compared the average daily step count data by ADHD medication status,
there were no differences between groups (Figure 1). Among children with
BPD, the mean (standard deviation) daily step count of the 3/5 children
who were taking ADHD medication for whom a valid step count was
available, was 15772 (5054) compared to 16416 (4288) in the 21 children
who were not taking ADHD medication (Figure 2).