Skip to main content

Advertisement

Table 6 Vitamin C and FEV1: effect modification by age and exposure to dampness

From: Vitamin C and asthma in children: modification of the effect by age, exposure to dampness and the severity of asthma

Age (yr) Exposure to dampness in the bedroom No of. Childrena) FEV1 (L/s) Percentage increment in FEV1 b)
    Placebo Vitamin C Mean 95% CI
7.0-8.2 Never 10 0.98 1.34 37.0% 33.9-40.2%
  During past 1 yr 11 1.04 1.34 29.0% 27.4-30.6%
  Earlier 9 0.99 1.25 27.1% 21.5-32.6%
8.3-10 Never 15 1.28 1.66 29.3% 27.6-31.1%
  During past 1 yr 9 1.21 1.52 25.9% 22.5-29.4%
  Earlier 5 1.23 1.49 21.3% 18.0-24.5%
  1. a) Since the goal of this table is to compare the effect of "During past 1 yr" and "Earlier" exposure to dampness, one child who had both modes of exposure was excluded (age 8.4 yr), making the number of children in this analysis 59.
  2. b) When age as a continuous variable and the three categories of dampness were included in the linear model explaining the effect of vitamin C on the FEV1 increase, the model was improved by χ2(3 df) = 51.8, P = 10-10 (model parameters are shown in Table 7). There was no second order interaction between age and dampness in their modification of the vitamin C effect (χ2(2 df) = 2.3, P = 0.3).