Table 4

 Geometric mean cotinine concentrations and 95% confidence intervals by number of parent figures who smoke, adjusted for age and family affluence, before and after smoke-free legislation in Scotland

Parental smoking status20062007Ratio (95% CI) of mean cotinine concentration 2007:2006 P value
Mean (95% CI) cotinine concentration (ng/ml)No (%)Mean (95% CI) cotinine concentration (ng/ml)No (%)
Neither parent figure smokes0.14 (0.13 to 0.16)1240 (59.6)0.07 (0.06 to 0.08)1140 (58.3)0.49 (0.42 to 0.56)<0.001
Father figure only smokes0.57 (0.47 to 0.70)218 (10.5)0.32 (0.25 to 0.42)226 (11.6)0.56 (0.41 to 0.77)<0.001
Mother figure only smokes1.38 (1.18 to 1.62)309 (14.9)1.23 (1.03 to 1.48)301 (15.4)0.89 (0.71 to 1.13)0.314
Two parent figures smoke1.94 (1.71 to 2.21)312 (15.0)1.74 (1.51 to 2.00)287 (14.7)0.89 (0.74 to 1.08)0.173
Total0.35 (0.32 to 0.38)20790.21 (0.19 to 0.23)19540.60 (0.53 to 0.68)<0.001

Cotinine confirmed non-smokers.