Quality of online heatstroke information across four countries: a quantitative content analysis

Effective heatstroke prevention depends not only on access to information but also on whether online health materials support understanding and actionable decision-making. However, evidence comparing the quality and presentation of online heatstroke information across countries remains limited. We conducted a quantitative content analysis of 120 publicly available heatstroke-related webpages from Japan, the United States, the United Kingdom, and Australia (30 per country), with one World Health Organization webpage included as a reference. Readability, information volume, credibility, and information presentation were assessed using established metrics, including the Patient Education Materials Assessment Tool for Print Materials. Cross-country comparisons and sensitivity analyses focusing on webpages targeting the general public were performed. UK webpages showed higher readability, whereas Japanese webpages more frequently incorporated visual aids and tools that facilitate preventive actions, resulting in higher understandability and actionability scores. However, actionability did not reach adequate levels in any country. Online heatstroke information differs substantially across countries. While readability improves accessibility, greater integration of visual and action-supporting design elements is needed to better promote preventive action.