Cigarette pack sizes and smoking

Posted: July 19, 2021 By:

Smoking remains one of the largest risk factors for preventable disease and is also one of the major contributors to the gap in life expectancy and years lived in good health between the most and least affluent groups.

The size of a pack is one of the last few ways that tobacco companies can directly encourage smoking. Read more about the need for evidence to show whether capping cigarette pack sizes would help people to cut down their smoking here.

In this study, we asked half of 124 Australian smokers to continue smoking from their usual size of cigarette packs (25 cigarettes or more per pack) and half to switch to using packs of 20 cigarettes for four weeks.

It was the first study to test the impact of capping pack sizes at 20. We used an adaptive design, which means that part-way through data collection, an interim analysis was conducted to assess how many more participants would need to be recruited for the study to have enough statistical power to detect an effect of pack size.

The planned interim analysis, conducted when 124 participants had been randomised, suggested 1122 additional participants needed to be randomised for sufficient power to detect an effect. This exceeded the pre-specified number of participants that was feasible for us to recruit so we stopped collecting data. Analysis of the collected data revealed the data were consistent with there being no change in the number of cigarettes smoked per day between participants smoking from packs of 20 versus those smoking from pack sizes of 25 or greater, although the observed reduction was in the expected direction.

It remains unclear whether reducing cigarette pack sizes from ≥25 to 20 cigarettes reduces smoking. Importantly, the results of this study provide no evidence that capping cigarette pack sizes would be ineffective at reducing smoking.

This study highlights the need for a suitably-sized study to address the lack of experimental evidence on the impact of large cigarette pack sizes on smoking. Such a study is in progress (https://doi.org/10.1186/ISRCTN16013277) with results expected by December 2021.

To read the findings of the study in full click here.

Lee, I., Blackwell, A.K.M., Scollo, M., De-Loyde, K., Morris, R.W., Pilling, M.A., Hollands, G.J., Wakefield, M., Munafò, M.R. & Marteau, T.M. Cigarette pack size and consumption: an adaptive randomised controlled trial. BMC Public Health21, 1420 (2021). https://doi.org/10.1186/s12889-021-11413-4

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