Table 3

Sensitivity analysis

Sensitivity to the covariates included and how they are modelled
Model 1: covariate adjustment equivalent to model 5, table 2Model 2: all non-significant covariates in table 1 added to model 1Model 3: all continuous covariates in model 1 dichotomised at median splitModel 4: removal of 2 plausible mediators—media parenting and friend smoking—from model 1
Sensitivity to how film-smoking exposure is modelled
Exposure to film smoking
Modelled as a continuous variable
 Scaled so lowest is 0 and highest is 1
  All values >95th percentile set at 95 percentile2.08(1.22 to 3.55)2.09(1.21 to 3.61)2.63(1.66 to 4.18)
  No outlier trimming2.95(1.37 to 6.36)
 Scaled so that median value is 1
  All values >95th percentile set at 95 percentile1.29(1.07 to 1.55)
  No outlier trimming1.25(1.07 to 1.47)
Modelled as dummy variables
 Quartiles of exposure
  Quartile 1RefRef
  Quartile 20.91(0.60 to 1.37)1.10(0.78 to 1.58)
  Quartile 31.25(0.83 to 1.88)1.45(1.02 to 1.06)
  Quartile 41.49(1.00 to 2.22)1.91(1.35 to 2.70)
 Median split
  Below medianRef
  Median or above1.44(1.08 to 1.92)1.54(1.18 to 2.01)