Table 5

Multiple linear regression analysis of the relation between cotinine concentration (ln) and smoking restriction type, survey year, presence of a parental smoker, family affluence and age, Scotland

CoefficientLinearisedtp>t95% CI
standard error
Parental smoking status
At least one parental smoker1.2010.10711.19<0.0010.988 to 1.415
Survey year
2007−0.6930.071−9.71<0.001−0.835 to −0.551
Type of smoking restriction
Partial0.4050.0984.13<0.0010.210 to 0.600
None0.7190.2373.040.0030.248 to 1.190
Family affluence
Low0.4110.0616.70<0.0010.289 to 0.533
Medium0.0800.0651.230.220−0.049 to 0.210
Restriction type by survey year interaction
Partial× 20070.4030.1113.620.0010.181 to 0.625
None× 20070.5600.1334.19<0.0010.295 to 0.825
(Complete restrictions and 2006 are reference categories)
Restriction type and presence of parental smokers interaction
Partial×at least one parental smoker0.6300.1344.71<0.0010.364 to 0.896
None×at least one parental smoker0.7820.2533.090.0030.280 to 1.284
(Complete restrictions and no parental smokers are reference categories)
Age (years)−0.0800.067−1.190.238−0.214 to 0.054
Constant−1.3310.771−1.730.088−2.863 to 0.202