Table 2

Multiple logistic regression analysis using all studies in UK and Australia, as for Table 1, with interaction term (country × year)

Variable

Odds Ratio (95% CI)

p-value

Country [UK (reference) versus Australia]

1.406 [1.379, 1.433]

p < 0.0005

Year of survey

1.032 [1.030, 1.034]

p < 0.0005

Age of children surveyed

0.993 [0.989, 0.997]

p = 0.016

Parental-response (reference) vs Self-complete

1.239 [1.197, 1.283]

p < 0.0005

ISAAC study [No (reference) versus Yes]

1.649 [1.609, 1.690]

p < 0.0005

Country by Year interaction

0.938 [0.933, 0.943]

p < 0.0005

Patel et al. Environmental Health 2008 7:57   doi:10.1186/1476-069X-7-57