Effectiveness and acceptability of interventions to improve readability of patient healthcare materials: A narrative systematic review

OBJECTIVES: Reading age is a key component of Health literacy (HL) yet many written healthcare materials in the UK exceed recommended reading levels, making them less accessible to much of the population. Creating barriers to understanding contributes to health inequalities. Simplifying the way information is written and terminology used could be a useful and low-cost approach to support HL, yet effectiveness of such interventions remains unclear. This study aims to systematically review evidence evaluating the effectiveness and acceptability of healthcare material readability interventions in high income countries. STUDY DESIGN: Narrative systematic review. METHODS: Searches of CENTRAL, Embase, MEDLINE, CINAHL, ERIC, APA Psych Articles, and Psychology and Behavioral Science, databases from 2014 to 2024 were conducted. Articles title/abstract and full text were double screened. Eligible studies examined tailored or improved written healthcare materials across clinical specialities. Data extraction included study characteristics, and interventions', impact on patient acceptability, comprehension and health outcomes. The Mixed Methods Appraisal Tool (MMAT) was used for critical appraisal. RESULTS: Thirty studies were included, predominantly from the USA. The majority evaluated interventions using simplified language, structured formatting, or visual enhancements. Findings indicated that simplified content was associated with greater patient understanding and preference. However, evidence on behavioural adherence and direct health outcomes was mixed, with few studies demonstrating statistically significant improvements. Quality of included studies was generally low, with methodological and reporting limitations. CONCLUSIONS: Readability interventions can enhance patient comprehension and acceptability, yet their long-term impact on health outcomes remains uncertain. Future research should assess sustained effects and explore routine implementation in healthcare settings to inform best practices.