Summary of findings 4. Population‐level impact of heated tobacco on cigarette smoking prevalence.

Population‐level impact of heated tobacco on cigarette smoking prevalence
Patient or population: N/A Setting: Japan Intervention: introduction of heated tobacco to market Comparison: N/A
Outcomes	Impact	№ of participants (studies)	Certainty of the evidence (GRADE)
Cigarette sales – assessed with national and regional sales data	1 study found that the yearly percentage decline in cigarette sales accelerated after the introduction of heated tobacco in Japan, increasing from a mean decline of −3.10% across 2011–2015 to −16.38% across 2016–2019. A second study found similar results using a different method; it found that per capita cigarette sales were increasing at a rate of 0.10 to 0.14 (depending on statistical approach) per month before the introduction of heated tobacco in Japan. After the introduction, they declined at a rate of 0.63 to 0.66 cigarettes per month.	N/A (2 observational studies)	⊕⊝⊝⊝ Very lowa,b
N/A: not applicable/available.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aDowngraded one level for indirectness: cigarette sales do not necessarily translate to reductions in smoking prevalence, as smokers may reduce the amount they smoke rather than stop smoking entirely.
^bDowngraded one level for risk of bias: one study was considered to be at serious risk of bias, while the other was deemed at moderate risk.