The impact of strengthening cigarette pack warnings: Systematic review of longitudinal observational studies

Objectives: Cigarette pack warnings are a tobacco control strategy used globally. To understand their impact, we systematically reviewed longitudinal observational studies examining national implementation of strengthened warnings. Methods: We used comprehensive search procedures to identify observational studies examining the impact of strengthening cigarette pack warnings. We report longitudinal changes in knowledge, beliefs, attitudes, intentions, and behavior. Results: We identified 32 studies conducted in 20 countries with 812,363 participants. Studies commonly examined changes from text to pictorial warnings (64%); the remainder examined strengthened text or strengthened pictorial warnings. Knowledge increased in all 12 studies that assessed it. Studies of beliefs/attitudes and intentions showed mixed results. Quitline calls increased in four of six studies, while foregoing of cigarettes did not increase. Cigarette consumption decreased in three of eight studies; quit attempts increased in four of seven studies; and short-term cessation increased in two of three studies. Smoking prevalence decreased in six of nine studies. Conclusions: Strengthening warnings was associated with longitudinal increases in knowledge, quitline calls and reductions in smoking behavior. Strengthening warning policies should be a priority for tobacco control globally. (C) 2016 The Authors. Published by Elsevier Ltd.