Interpretation of findings
A reduction in cigarettes smoked is an appropriate aim for tobacco control policy if it leads either to direct or indirect health benefits. Therefore, one critical question is whether the magnitude of reduction observed in this study is likely to translate to population health benefit. A decrease of 1.3 cigarettes per day, or fewer than 10% of usual cigarettes smoked, is unlikely to confer any direct reduction in risk due to decreased exposure. First, smoking reduction studies suggest that a minimum reduction of 50% consumption is required to reduce indicators of risk [There is evidence that smoking fewer cigarettes per day—which may be a marker of lower dependence—increases the probability of cessation. Smoking one fewer cigarette per day at baseline was estimated in one study to increase the chances of being a former smoker by between approximately 7 and 11% [Motivation to stop smoking was low in this sample of smokers—that is, below the mid‐point of a scale for motivation to stop smoking—reflecting the inclusion criterion that participants did not intend to quit smoking in the next 3 months. An unpredicted interaction between pack size and order was found, such that motivation to stop smoking increased from intervention period 1 to intervention period 2 regardless of which pack size was used first, and participants who were allocated to use packs of 20 cigarettes first had lower motivation to stop smoking at the end of both intervention periods compared to participants who were allocated to use packs of 25 cigarettes first.