Fig. 3

Serum 25-hydroxyvitamin D (25OHD) levels over 7 months. The 25OHD values are presented by group at various time points. a Crude total serum 25OHD in the vitamin D (filled boxes) and control (open boxes) groups over the 7-month study period. The median is depicted by the horizontal bar, with the lower and upper limits of each box representing the 25% and 75%; these numerical values are also recorded in the lower panel as median (25%, 75%) at each time point. Error bars represent the minimum and maximum of the distribution. b Adjusted marginal means for the total serum 25OHD are presented in the vitamin D (filled circles) and control (open squares) groups over the 7-month study period, after adjustment for asthma phenotype, sex, ethnicity, environmental tobacco exposure, school-days missed, baseline vitamin D intake, baseline serum 25OHD, and asthma management strategy. Error bars represent the 95% confidence interval of the mean. In the lower panel, their numerical values are recorded by group at each point in time along with the adjusted mean group difference (95% CI). Using a generalised linear mixed model, a statistically significant overall group (p < 0.0001), time (p < 0.0001), and group*time (p < 0.0001) interaction was documented. In both graphs, the dotted line represents the 75 nmol/ L on the y-axis. Total 25OHD was comprised overwhelmingly of 25-hydroxyvitamin D₃, with 3-epimer-25-hydroxyvitamin D₃ and 25-hydroxyvitamin D₂