Cigarette pack size and consumption: an adaptive randomised controlled trial

Abstract

Background Observational evidence suggests that cigarette pack size – the number of cigarettes in a single pack – is associated with consumption but experimental evidence of a causal relationship is lacking. The tobacco industry is introducing increasingly large packs, in the absence of maximum cigarette pack size regulation. In Australia, the minimum pack size is 20 but packs of up to 50 cigarettes are available. We aimed to estimate the impact on smoking of reducing cigarette pack sizes from ≥25 to 20 cigarettes per pack. Method A two-stage adaptive parallel group RCT in which Australian smokers who usually purchase packs containing ≥25 cigarettes were randomised to use only packs containing either 20 (intervention) or their usual packs (control) for four weeks. The primary outcome, the average number of cigarettes smoked per day, was measured through collecting all finished cigarette packs, labelled with the number of cigarettes participants smoked. An interim sample size re-estimation was used to evaluate the possibility of detecting a meaningful difference in the primary outcome. Results The interim analysis, conducted when 124 participants had been randomised, suggested 1122 additional participants needed to be randomised for sufficient power to detect a meaningful effect. This exceeded pre-specified criteria for feasible recruitment, and data collection was terminated accordingly. Analysis of complete data (n = 79) indicated that the mean cigarettes smoked per day was 15.9 (SD = 8.5) in the intervention arm and 16.8 (SD = 6.7) among controls (difference − 0.9: 95%CI = − 4.3, 2.6). Conclusion It remains unclear whether reducing cigarette pack sizes from ≥25 to 20 cigarettes reduces cigarette consumption. Importantly, the results of this study provide no evidence that capping cigarette pack sizes would be ineffective at reducing smoking. The limitations identified in this study can inform a more efficient RCT, which is urgently required to address the dearth of experimental evidence on the impact of large cigarette pack sizes on smoking. Trial registration 10.1186/ISRCTN34202533

Cigarette pack size and consumption: a randomized cross‐over trial

“…The within‐person standard deviation (SD) of cigarettes smoked per day obtained in our previous study [ 9 ] was used to calculate that, with 80% power, we would detect a difference of 1.5 cigarettes smoked per day (which is a size of importance to detect, and consistent with previous research, Lee et al 2021) as significant at a two‐sided significance level of 5%, with 210 participants available for analysis (105 per sequence group). To account for potential attrition, 252 participants were recruited for randomization.…”

“…In an earlier parallel group study using a two‐stage adaptive design we randomized smokers in Australia, who usually purchased cigarettes in packs of at least 25, to smoke for 4 weeks either from their usual pack size or from packs of 20 cigarettes. At the interim assessment stage (when 124 participants had been randomized) this adaptive trial was halted as the estimated required total sample of more than 1000 exceeded pre‐specified criteria for feasible recruitment [ 9 ]. A cross‐over design, making within‐group comparisons, was deemed more efficient, as these typically require smaller numbers of participants.…”

Small/Kiddie Cigarette Packaging Size and Its Impact on Smoking: A Systematic Review

“…Tobacco companies introduced kiddie packs into the market with the claim that they might support moderation and encourage smoking cessation among heavy smokers [9]. A study revealed that cigarette consumption per day was positively associated with pack size [10]. In addition, small cigarette packs are used by some smokers as a method of controlling their consumption [10].…”

“…A study revealed that cigarette consumption per day was positively associated with pack size [10]. In addition, small cigarette packs are used by some smokers as a method of controlling their consumption [10]. Nevertheless, there is still a lack of experimental evidence for a causal relationship between pack size and consumption [10].…”

“…In addition, small cigarette packs are used by some smokers as a method of controlling their consumption [10]. Nevertheless, there is still a lack of experimental evidence for a causal relationship between pack size and consumption [10]. On the other hand, the affordability of kiddie packs would encourage smoking among the lower income groups, mainly teens and minors [5].…”