The effect of adding visual summaries to data visualizations on patient judgments of hypertension control

To test the impact of visual summaries of blood pressure (BP) data (eg, stoplight and gradient displays), within the context of a patient-facing digital application connected to the EHR, on patient judgments about hypertension control.

Participants (N = 117; Internet sample of patients with hypertension) viewed graphs depicting BP data for fictitious patients. For each graph, participants rated perceived hypertension control, risk of heart attack and stroke, urgency, worry, and perceived understanding of health implications on a 0-100 slider bar and indicated the preferred action to take in response this BP data (eg, talk to doctor at next appointment, go to hospital immediately). Using a within-subjects design, all participants evaluated 12 graphs with data that varied in systolic BP mean (controlled or uncontrolled) and standard deviation (moderate or high) and included three different types of visual summaries: (1) control (average BP only), (2) stoplight, (3) gradient. Participants also completed the Graph Literacy-Short Form and the Electronic Health Literacy Scales (eHEALS).

Measures of perceived risk of heart attack and stroke, urgency, and worry were significantly greater and perceived hypertension control was significantly lower for cases where hypertension was uncontrolled P < 0.05. However, there were no significant differences between visual summary methods on the primary outcomes. Graph literacy and electronic health literacy were globally related to judgments of hypertension control but did not interact with any of the study factors.

The verbal summary, stoplight, and gradient displays performed similarly despite the addition of more precise risk information.