Re-analysing tobacco industry funded research on the effect of plain packaging on minors in Australia: Same data but different results

INTRODUCTION: Our objective was to re-analyse the data used in an industry-funded working paper to study the effect of plain packaging on youth smoking prevalence in Australia, allowing for other tobacco control measures introduced over the period 2001-2013, and using a more appropriate method of analysis. METHODS: Monthly smoking prevalence and sample sizes from repeat cross-sectional surveys were reconstructed from the working paper by reverse engineering of the industry-presented data, and analysed as a time series using logistic regression. Power analysis presented in the industry-funded working paper was re-calculated. RESULTS: Smoking prevalence among minors in Australia declined from 11.6% to 5.6% over the 13-year period examined; an overall 52% relative reduction or an average annual reduction of 5.5% (95% confidence interval 4.6% to 6.4%). There was a 12.1% (-4.8% to 26.2%) relative reduction in smoking prevalence when plain packaging was introduced, though the reduction was not statistically significant. Re-calculated power values were much lower than those reported in the industry-funded paper, confirming the inconclusiveness of its findings, as pointed out in previous critiques. CONCLUSIONS: Our findings suggest a decline of smoking prevalence in minors following the introduction of plain packaging in Australia. They differ substantially from those presented in an industry-funded study on the effects of plain packaging on smoking prevalence in minors in Australia, which used the same data.