Introduction
The most feared complication of atrial fibrillation (AF) is an ischemic stroke. If detected in time, the administration of anticoagulation therapy can reduce the risk of stroke by about two-thirds. Detection and diagnosis of AF is currently done with electrocardiography (ECG). Unfortunately, ECG is not sufficiently effective due to its low availability caused by the need of dedicated hardware. The low-cost, user-friendliness, and widely spread smartphone technology in the population make photoplethysmography a more effective tool to detect AF, and thereby an important step in stroke prevention. 

Objective
This work investigates the effect of age on the usability of a PPG-based smartphone application.

Methods
A usability test was performed on 95 participants divided in three age categories; young adults (18-29), adults (30-65) and pensioners (65+). Participants were instructed to use the application and perform critical tasks with minimum supervision or assistance. The tasks included multiple functionalities of the app (e.g. downloading, create an account, perform a measurement, add context, log-in, etc.). Time to perform each task and amount of insufficient quality measurements were documented. Subjective usability estimation was inquired via a survey. 

Results
Although all critical tasks were completed successfully by all participants, significant differences were observed between the time required to perform each task. In general, the elderly required more time to perform a task and reported higher difficulty levels in the subjective usability estimation. No significant difference was found between the groups regarding the number of insufficient quality measurements.

Conclusion
Although there is a difference in time to perform tasks and in the difficulty experienced between age categories, it does not affect the usability of the smartphone application. These results demonstrate that the relevant target groups can be reached when using a smartphone application as a screening device.