Introduction Adding messages to cigarette health warning labels (HWLs) about the harms of smoking increases awareness of these health facts, but little is known about the impact of removing messages. This is the first study to directly investigate the impact of adding and removing messages from cigarette HWLs on smokers’ awareness of harms.
Methods Data were drawn from nine waves of the International Tobacco Control (ITC) Canada Survey, a national representative cohort of adult smokers (n=5863) conducted nearly annually between 2002 and 2013–2014. Two analytical approaches were conducted: generalised estimating equation (GEE) regression models estimated adjusted percentages of correct smoking-related health statements at each wave and segmented regression analyses modelled temporal trends in awareness before and after the revisions by measuring the difference in slopes.
Results Adding messages to HWLs significantly increased awareness that smoking causes blindness (OR=3.36 (95% CI 2.71 to 4.18); p<0.001; estimated increase of 1.01 million smokers in Canada) and bladder cancer (OR=2.14 (95% CI 1.71 to 2.66), p<0.001; estimated increase of 1.09 million smokers). Adding the warning that nicotine causes addiction did not significantly impact smokers’ awareness. Removing messages was shown to decrease awareness that cigarette smoke contains carbon monoxide (OR=0.53 (95% CI 0.41 to 0.70), p<0.001; estimated decrease of 342 000 smokers) and smoking causes impotence (p=0.007 for the difference in slopes; estimated decrease of 354 000 smokers).
Conclusions Adding messages to HWLs increases smokers’ awareness of health facts, but removing messages decreases awareness. These findings demonstrate the importance of carefully considering the implications of adding and especially removing messages from HWLs and the importance of regularly revising warnings.
- packaging and labelling
- public policy
- surveillance and monitoring
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Contributors ACG led in designing the study and writing the manuscript. ACG and PD conducted the statistical analyses. GTF, PD, SMN and DH contributed to the revision of the draft. The final version of this paper was reviewed and approved by all coauthors.
Funding The International Tobacco Control Canada Project was supported by grants from the US National Cancer Institute (R01 CA100362, R01 CA090955, P50 CA111236 (Roswell Park Transdisciplinary Tobacco Use Research Center) and P01 CA138389); the Canadian Institutes of Health Research (CIHR) (MOP57897, MOP-79551 and MOP-115016); and the Canadian Tobacco Control Research Initiative (014578). Additional support in preparing this paper was provided to University of Waterloo by CIHR (FDN-148477). ACG was supported by the CIHR Doctoral Award – Frederick Banting and Charles Best Canada Graduate Scholarship (CGS-D) (#118068). DH is supported by a CIHR-Public Health Agency of Canada Applied Public Health Research Chair. GTF was supported by a Senior Investigator Grant from the Ontario Institute for Cancer Research and a Senior Prevention Scientist Award from the Canadian Cancer Society Research Institute.
Competing interests DH has served as an expert witness in legal challenges against tobacco companies. DH and GTF have served as expert witnesses on behalf of governments in litigation involving the tobacco industry.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement All data relevant to the study are included in the article or uploaded as supplementary information.