Table 4

 Mean (95% confidence interval, n) cotinine concentrations

Cotinine (ng/ml)Baseline3 month6 month12-monthp Value*Trend†
*p Values from baseline to 12 month follow up Wilcoxon sign rank test.
†p Values from Cuzick non-parametric trend test across all waves.
Mean cotinine3.6 (2.56 to 4.67) 241.7 (1.44 to 2.0) 241.9 (1.42 to 2.3) 240.78 (0.37 to 1.19) 24<0.001<0.001
Mean cotinine (excludes respondents with undetectable cotinine at baseline)4.7 (3.36 to 5.98) 161.8 (1.41 to 2.25) 162.02 (1.35 to 2.69) 160.83 (0.27 to 1.4) 16<0.001<0.001