Date Published: November 7, 2014
Publisher: Public Library of Science
Author(s): Sanmitra Bhattacharya, Padmini Srinivasan, Phil Polgreen, Patrick S. Sullivan.
To investigate factors associated with engagement of U.S. Federal Health Agencies via Twitter. Our specific goals are to study factors related to a) numbers of retweets, b) time between the agency tweet and first retweet and c) time between the agency tweet and last retweet.
We collect 164,104 tweets from 25 Federal Health Agencies and their 130 accounts. We use negative binomial hurdle regression models and Cox proportional hazards models to explore the influence of 26 factors on agency engagement. Account features include network centrality, tweet count, numbers of friends, followers, and favorites. Tweet features include age, the use of hashtags, user-mentions, URLs, sentiment measured using Sentistrength, and tweet content represented by fifteen semantic groups.
A third of the tweets (53,556) had zero retweets. Less than 1% (613) had more than 100 retweets (mean = 284). The hurdle analysis shows that hashtags, URLs and user-mentions are positively associated with retweets; sentiment has no association with retweets; and tweet count has a negative association with retweets. Almost all semantic groups, except for geographic areas, occupations and organizations, are positively associated with retweeting. The survival analyses indicate that engagement is positively associated with tweet age and the follower count.
Some of the factors associated with higher levels of Twitter engagement cannot be changed by the agencies, but others can be modified (e.g., use of hashtags, URLs). Our findings provide the background for future controlled experiments to increase public health engagement via Twitter.
Government agencies are increasingly interested in using social media to distribute information at the national, state and local levels. U.S federal agencies, for example, routinely use a variety of social media sites including Twitter, Facebook, YouTube, Flickr, and Instagram to enhance communication . In addition to distributing information, government agencies are increasingly interested in interacting with the populations they serve. For example, new guidelines entitled “Digital Governmental Strategy” outline specific steps for governmental agencies to make digital information more “customer centric” . This bidirectional form of communication can be defined as engagement: interactions designed to promote some common goal .
The U.S. government uses several social media services, but Twitter is one of the most commonly used service. Recent estimates indicate that approximately 18% of online adults use Twitter , and over 500 million users around the globe  generate over 500 million tweets per day . Given the widespread use of Twitter and the fact that people are increasingly using it to share their experiences with illness and treatments as well as other health concerns , Twitter provides a potentially valuable stream of health-related information. Several studies have used Twitter to discover adverse drug reactions , , perform surveillance for disease activity ,  and health beliefs , . Twitter has also been used to investigate general health behavior , . However, few studies have focused on how health agencies use Twitter. The studies that do exist describe activity consistent with distributing information with little attention paid to engagement . One of the few studies on engagement via Twitter focuses on levels of engagement: low (have followers), medium (promote retweeting) and high (have offline interactions) . In contrast, to previous studies, our goal is to determine the factors associated with engagement of federal agencies with the “Twitter Public”. The caveat to note is that while we focus on public engagement an agency may be equally or even more interested in information dissemination alone.
Our results show that although multiple federal health agencies are using Twitter, there is a great deal of difference between levels of Twitter use and also retweets. For public health agencies, we found that a tiny minority of tweets gets more than 100 retweets; a two-thirds majority of tweets get on average 8 retweets. We also found that a handle’s follower count and favorite count have strong positive relationships with retweeting behavior. While these features are not easy for agencies to improve, they are easy metrics to follow. In contrast, we found that having more friends on Twitter was negatively associated with the number of times a tweet is retweeted.
Our study has a few limitations. First, it is comprised of observational data; i.e., we did not run formal experiments. Thus although we can describe associations, we cannot establish causality. For example, while we find that the number of followers is associated with retweeting, we cannot insure, due to the descriptive nature of the study, that increasing the number of followers will lead to an increase in retweets. Second, although we captured the majority of tweets from federal agencies we could only collect a maximum of 3200 for each handle, so for a few of these agency handles (18/130), our data was censored. Nevertheless, we still had a large corpus of tweets over a long period of time. Third, the intent behind some tweets may simply be to inform and not necessarily to engage via retweeting. We do not know about an organization’s motivations for tweeting or for posting specific tweets or the targeted audience. Furthermore, some agencies may have more information that naturally draws the public. Thus, these results do not represent a “report card” on these agencies. Fourth, our definition of engagement is limited to examining retweeting and its features. Fifth, although we considered various important and typically used tweet-based features in our statistical analysis, there may be other key features. For example, while time or day of the week may have significant effects on tweeting or retweeting behavior ,  and hence engagement, these features were considered outside the scope of our study. We also did not examine the features of the retweet. For example, a retweet may agree with or contradict the message in the source tweet. Finally we limit our analysis to Twitter, and there are other social network platforms that federal agencies are using.
We present the first comprehensive analyses of Twitter engagement by public health agencies. The level of Twitter activity varies greatly by health agency: some health accounts are very active and others are not as much. However, it seems to be the content of the Tweets (e.g., about activities and behaviors, disorders) and not the number of tweets alone that is associated with a higher level of engagement (number of retweets). Furthermore, although some of the factors associated with more engagement cannot be changed by the agency (e.g., the length of time they have been active on Twitter), several factors associated with higher retweets can be controlled (e.g., use of hashtags, URLs). Our results provide a framework for future experiments designed to improve the public’s engagement with health agencies via Twitter.