Publication Date



Open access

Embargo Period


Degree Type


Degree Name

Doctor of Philosophy (PHD)


Industrial Engineering (Engineering)

Date of Defense


First Committee Member

Sara J. Czaja

Second Committee Member

Joseph Sharit

Third Committee Member

Shihab Asfour

Fourth Committee Member

Robert Schwartz

Fifth Committee Member

Dan Morrow


Diverse patient populations are increasingly using patient portals that are tethered to their electronic medical record (EMR). Patients using portals can view their medical history, review laboratory results and medication lists, and follow links to credible health information online. Many of the tasks performed with a portal depend on numeracy skill. For example, numeracy skill is needed in managing appointment dates and times, understanding medication dosage instructions, reviewing lab results, and interpreting health information from charts, tables, and graphs. However, there is no data available regarding the numeracy ability of patients and how this ability affects their use of a patient portal. Additionally, little is known about how other individual characteristics, such as age and cognition, impact the ability of patients to use the information contained in portals to manage their health. The specific aims of this study were to: 1) examine the ability of middle-aged and older adults to use a patient portal of an EMR to perform common health management tasks; 2) examine the relationships between individual characteristics such as age, cognitive abilities, health numeracy, and task performance; 3) identify usability problems inherent in the use of patient portals; and 4) identify initial design solutions. This study evaluated the ability of 107 middle-aged and older adults (aged 40-85 years, M = 58.87, SD = 11.89) to use a simulated patient portal of an EMR to perform 15 common health management tasks encompassing medication management, review/interpretation of lab/test results, and health maintenance activities. Results indicated that older adult participants had lower mean scores on the more complex tasks and overall performance than did the middle-aged adults. Individual characteristics such as age, cognitive variables, health numeracy, and Internet experience had a significant impact on performance for both the middle-aged and older adults. Individuals with lower verbal ability, executive functioning, reasoning skills, and health numeracy skills had lower performance. Overall, the findings indicated that demands on these skills should be considered in the design of patient portals. In addition, careful consideration needs to be given to health numeracy demands such as the presentation of numerical information and demands related to interpretation of mathematical information. This research is unique and important in terms of addressing barriers to older adults’ use of patient portals of EMRs. We must know more about these users and their preferences and usability problems if we expect them to adopt and successfully use these systems. Currently, the literature available on this topic is very limited. Results will also contribute to the existing literature on the health numeracy aspect of health literacy. Although there is a vast amount of literature on health literacy, there is only limited information about older adults and health numeracy. This project is very timely and of great public health significance because the number of older patients using patient portals tethered to an EMR is likely to increase as electronic records become more widely used.


Objective numeracy ability; patient portals; self-management of health; simulation methods; subjective numeracy ability