Table 2

Influence of non-smoking factors on frequency of asthma contacts: univariate analysis

Factor n IRR CI (95%) Model χ2 df p value
BTS step
 1 831.00
 2 491.701.35 to 2.16
 32721.881.58 to 2.25
 4 & 5 342.772.21 to 3.4886.883<0.0001
Age of child (years)
 2–3 491.00
 4 440.740.06 to 0.90
 5–71470.620.53 to 0.73
 8–101290.510.43 to 0.60
 11–12 340.400.32 to 0.4995.514<0.0001
Perceived severity of asthma
 Very mild 961.00
 Mild1811.130.96 to 1.32
 Moderate1281.611.37 to 1.89
 Severe 281.661.32 to 2.10
 Very severe  63.662.69 to 4.9890.914<0.0001
Age of index parent (years)
 <25 331.00
 26–301260.800.65 to 0.97
 31–351480.710.58 to 0.86
 36–40 800.670.54 to 0.84
 >40 510.720.56 to 0.9115.7440.003
Sex of child
 Male2901.00
 Female1481.121.00 to 1.253.7810.05
No of children in family
 1 921.00
 22081.030.89 to 1.18
 3 920.940.80 to 1.12
 4 460.750.60 to 0.9410.3930.02
  • IRR = the incidence rate ratio, the frequency of the number of contacts as a ratio of the frequency in the reference category (the first category of each factor).