Effectiveness of signage in preventing adolescents and young adults from accessing e-cigarettes in retail stores: a discrete-choice experiment

Background Displaying signage about the minimum legal age (MLA) for tobacco, including e-cigarette sales in retail stores, is a common public health strategy intended to reduce underage access. This study examines a variety of messages currently used in the USA to test the effects of specific components in signage on discouraging e-cigarette purchase among underage individuals. Methods A cross-sectional discrete-choice experiment asked 5326 adolescents and young adults, aged 13–24 years, to select from eight choice sets of hypothetical signs including different message attributes and images on retail storefronts. We analysed a total of 256 unique signs that varied in how they described tobacco, age, legal restrictions, whether and how images were included and whether there was a photo ID requirement. Results Signage was significantly more effective at discouraging underage e-cigarette purchases when it (1) explicitly referred to e-cigarettes as ‘liquid nicotine, electronic cigarettes or vapour products’ listed among other tobacco products (vs tobacco), (2) displayed the age limit (‘under 21’), (3) described legal restrictions, especially when using the word ‘penalties’, (4) stated ‘Photo ID required’ (vs not), and (5) included product images (vs not)—especially colour images. Participants under 21 were significantly more sensitive to colour images, the ‘penalties’ descriptor, and to a photo ID requirement. In addition, female participants were more sensitive to a ‘penalties’ descriptor compared with males, and non-Hispanic Black participants were less sensitive to an ‘illegal’ descriptor than non-Hispanic White participants. Conclusions Including effective content and images in existing signage informing the public about MLA of tobacco sales has potential to discourage under-age access to tobacco products.