Development and validation of a mobile health application usability scale for older adults with chronic diseases

Background Chronic diseases are one of the leading causes of disability and death in people over 60 years old. Mobile health applications can revolutionize healthcare delivery and management of chronic conditions and reduce healthcare costs. Unfortunately, many of these applications are not designed for elderly patients with chronic diseases. Therefore, it is crucial to create a reliable and specialized tool that developers and researchers can use to assess the usability of mobile (mHealth) applications designed specifically for elderly patients. Objective To develop and validate a mHealth application usability evaluation scale for elderly patients with chronic diseases. Methods We developed the first edition of the scale from March to September 2022 through literature review, interview, team discussion, and the Delphi method. Between October and December 2022, the improved scale after a pilot test was used to conduct surveys in Guangzhou, Guangdong, China, to analyze and screen items using the Item Discrimination Index, Correlation coefficient, Internal consistency test, and exploratory factor analysis. From October 2022 to February 2023, we completed the data collection and evaluation of the reliability and validity of the scale. Results The finalized scale included six dimensions and 23 items. Item-level content validity indices and the average scale content validity index ranged from 0.85–1. The validation evaluation showed that the scale has a good fit, with a χ2/df ratio of 1.728 and various fit indices ranging from 0.817–0.928. The values of Average Variance extraction and Composite Reliability also met the recommended criteria, with a value greater than 0.4 and 0.6, respectively. Additionally, the Cronbach's α coefficient for the full scale and subscales ranged from 0.758–0.911, indicating good internal consistency. Conclusions The usability scale for elderly patients with chronic diseases is a reliable and valid instrument. It fills gaps in existing tools, offering a comprehensive assessment of mHealth app usability among target audience. It has the potential to improve mHealth app design and promote age-appropriateness of healthcare delivery.