Literature Review

Introduction

“Health is a common issue for all human beings. As a consequence, everyone in the world has in some way to cope with the language of medicine” (Cappuzzo 2021, p. 37).

The language of medicine shapes how the public understands health and adjusts their behaviour. Plain language is a critical tool to present visual and written materials in clear and digestible ways for readers (Randell et al. 2025). Cappuzzo (2021) describes plain language in medicine as a set of reader-centred guidelines that address readers directly, use active voice and common words, and implement accessible design features such as lists, headers, and tables. 

Consequently, limited access to understandable health information can have a direct impact on the health of the population by hampering action and civic engagement (Rudd et al. 2004a). As individuals increasingly rely on the internet to find health information, there is a need for a shift from existing research on plain language in static materials to plain language in digital materials, where user engagement and comprehension vary (Sedgwick et al. 2021). 
 

Despite this trend, digital public health campaigns are relatively unexplored. Therefore, this literature review will examine the concept of plain language, existing research, the role of health literacy, challenges posed by the lack of trust and misinformation, and the rationale for future study of digital public health campaigns.

Understanding Plain Language

Plain language has been established to improve reading ease by its design to be understood the first time the audience reads or hears it (Stableford and Mettger 2007). In the context of health communications, the Centers for Disease Control and Prevention (2025) advocates for writing in active voice, choosing words that the audience is familiar with, limiting the average sentence length to twenty words and one idea, limiting paragraphs to five sentences and one topic, and using “you” and other pronouns. 
 

Building on this, plain language aligns with the cognitive load theory. Sweller et al (2011) demonstrated that when an audience is faced with new and complex information, difficulty comprehending information is not due to the contents, but rather due to how it is presented because readers must allocate more mental resources to decipher the information. 
 

Beyond increasing comprehension by improving readability, plain language can reduce health disparities faced by diverse populations and improve access to safe and quality care information and improved prevention and treatment of disease. As such, it is an integral part of the solution to major public health information problems (Stableford and Mettger 2007).
 

However, most research has been done on the effects of plain language in static written material, rather than digital communication formats that are prevalent on social media, as explored in the next section.

 

Existing Research on Plain Language in Health Communication

For the last two decades, efforts to simplify the language of health information using plain language have increased (Zarcadoolas 2011). Studies have shown that providing clear and simple language resources increases understanding and accessibility in how science is communicated (Sayfi et al. 2024).

 

Plain languages principles such as limiting sentence length can improve readability and reduce confusion (Sedgwick et al. 2021). Building on this, Randell et al. (2025) demonstrated that using plain language can help connect with audiences and inform and influence their understanding of healthcare. Furthermore, meaningful change is being driven in health literacy practice through the creation of guidelines on applying plain language principles to health information (Ayre et al. 2024). 

Nonetheless, studies such as those by Sayfi et al. (2024) and Stallwood et al. (2023) have focused on plain language provided in a static, written format. Both studies provide valuable insight on understanding but measuring actual behaviour and health outcomes were not feasible with these trials. Similarly, they report that plain language was preferred for accessibility and satisfaction, though the participants in the Stallwood et al. (2023) showed no significant difference in understanding, while the participants in the Sayfi et al. (2024) reported a higher understanding of the plain language texts. 

Moreover, despite including participants that are experts in their fields, there have been discrepancies noted about what plain language means in the context of health information (Harper and Zimmerman 2009). And while most studies have shown a preference for plain language, there have been mixed results when measuring outcomes. Consequently, even though the evidence favors plain language, the relationship between clarity and trust remains uncertain (Stableford and Mettger 2007). 

Despite the growing dominance of digital health information, these studies have not yet examined how plain language is used in an online context. This area remains key to supporting public health campaigns, as improved communication using plain language has the potential to improve care and subsequent outcomes (Rudd et al. 2004b), particularly when addressing the gap between functional health literacy and the readability of available materials, which is addressed in the next section.

 

Health Literacy as a Critical Factor

Health literacy determines how individuals interact with public health campaign materials. It is defined as “the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions” (Ratzan and Parker 2000, p. vi).
 

Consequently, limited health literacy in adults has been described as the “silent killer” (Zarcadoolas 2011) and “silent epidemic” (Warde et al. 2018) because of its link to poor health outcomes in the United States and across the globe. The link between health literacy and plain language begins at the message level: simple communication serves as a strategy to reach individuals with limited literacy skills (Warde et al. 2018).
 

To address this, there has an increase of published assessments of health materials that demonstrate a mismatch between the reading level of health materials and the reading ability of the average adult (Rudd et al. 2004a). Individuals with low health literacy preferred plain language, while those with high health literacy preferred standard language (Sayfi et al. 2024).
 

Nonetheless, as demonstrated by van Swol and Chang (2023), if a message is overly complex and uses scientific jargon, it may not be accessible. Instead, readers may rely on cues such as the credibility of the source of the message, but at the cost of understanding the information. Even among those who are well-educated, the use of medical jargon may still impede an individual’s understanding of health information (Peter et al. 2024).

 

Therefore, plain language can function as an equity tool that can help reduce disparities in access to health information, particularly when trying to reach culturally and linguistically diverse populations (Rudd et al. 2004a). 
 

However, as health campaigns move to digital platforms, there are new challenges to address beyond the differences in literacy levels: misinformation and distrust, described in the next section.

 

Digital Communication and the Challenge of Misinformation

Digital public health campaigns have wide reach, as Signorini et al. 2011 demonstrated when measuring public interest or concern about health in social media. They found that trends in social media users’ interest in hand hygiene and face masks timed with public health messages from the CDC.

However, information shared on digital media is often only processed superficially. For this reason, plain language is even more important to ensure understanding when users are rapidly consuming digital media alongside other stimuli. This underlines the need for guidance on digital health campaigns, especially when misinformation and disinformation threaten trust in public health (Randell et al. 2025). 

That is not to say that distrust is unfounded, as Randell et al. (2025) notes that the longstanding distrust in many communities is linked to historical trauma. Health information has been shared in a way that represents public relations rather than scientific engagement, often excluding individuals from low-income, minority ethnic groups (Lang et al. 2025). 

Because text that is easy to read and understand the first time is also more likely to be shared with others, using digital materials can help reach a wider audience and begin rebuilding this trust (Sedgwick et al. 2021).

Despite the emergence of digital public health campaigns, there is a lack of research on plain language in realistic digital environments, an issue that is addressed in the following section.

 

Research Gap and Rationale for Further Study

Current research examines static written materials with an emphasis on comprehension, with trust and behavioural intention explored as a secondary outcome (Sayfi et al. 2024; Stallwood et al. 2023). Addressing this gap between digital and static plain language is critical for designing digital public health campaigns that are inclusive and equitable.
 

More than half of internet users now go to the internet for health-related information (Sedgwick et al. 2021). Therefore, examining how people respond to plain language videos and infographics could provide insight on the link between digital plain language materials and understanding and trust. Existing research has shown that poorly designed digital campaigns might also contribute to health inequalities and limit their public reach (Ayre et al. 2024).
 

As a result, there is only the belief that the public will be prepared to take appropriate action in complex situations – and the action not been investigated (Zarcadoolas 2011). This forms the basis for future research and can have direct impact on public health campaigns in digital spaces.

 

Conclusions

The literature reviewed has shown plain language is more than just a stylistic choice. It is critical to ensuring the public can easily find what they need, understand what they find, and use the information (Randell et al. 2025).

 

These findings highlight the need for research that studies authentic digital environments measuring not just comprehension, but trust and behavioural intention.

 

Plain language is a public health strategy that drives clarity, trust, and action and is becoming a critical component of social media. This underlines the to understand just how plain language impacts engagement and its impact on digital public health campaigns.