• Kar-Hai Chu and Thomas W Valente.
• Department of Preventive Medicine, University of Southern California, Los Angeles, California, USA.
• BMJ Open. 2015 May 21; 5 (5): e007654.

ObjectiveThe sudden growth of e-cigarettes over the last decade has forced advocates and critics scrambling to bolster support for their respective sides. Bridging the divide in geographic barriers, social networking sites were an ideal meeting place for international activist communities, affording them the ability to organise events and discuss new topics in real time. This study examines how e-cigarettes are addressed in GLOBALink, an online international tobacco control community. We seek to discover if the pattern of activity in e-cigarette discussions changes over time. We are also interested in understanding the characteristics of sentiment toward e-cigarettes in discussion topics between countries with different network characteristics.DesignNetwork analysis to explore the relationships between members from different countries, and sentiment analysis of messages and threads to identify patterns of how different countries address e-cigarette topics.SettingGLOBALink, an online international tobacco control community.ParticipantsNetwork analysis based on GLOBALink members from 37 different countries. Sentiment analysis based on 853 posted messages, with over 1.4 million words.Outcome MeasuresNetwork centrality measures in country interaction data, including degree, closeness and betweenness. Sentiment scores for each message, and differences between country scores.ResultsThe network analysis found a core/periphery structure where central countries focused on active positive discussions pertaining to e-cigarettes, while isolated and peripheral countries posted negative topics without many responses. A qualitative examination of message topics suggests that general subjects elicit more interactions than those that are context specific.ConclusionsE-cigarettes are a polarising topic that can be seen in how countries appear to discuss related topics with others who share the same opinions. More work is needed to help communities stay informed of current research, and diffuse objective information. Network and sentiment analyses offer a strong combination of methodologies that can help support such efforts.Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

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