JMIR Publications

ABSTRACT

Background:

Fitness and physical activity patterns are key predictors of cardiovascular disease. Traditionally, these factors have been assessed through participant self-report, which is prone to recall bias and inaccuracy. Smartphone-based monitoring provides a scalable and objective alternative for measuring physical activity, offering improved accuracy over conventional assessment methods.

Objective:

To evaluated the feasibility of smartphone-based cardiovascular research in the Netherlands and to examine associations between objectively measured physical activity, perceived activity, functional capacity, life satisfaction, and cardiovascular risk.

Methods:

Adults in the Netherlands were recruited via the MyHeart Counts iPhone app between August 2022 and December 2023. Within the app, participants completed surveys, passively shared motion sensor data, and were invited to perform a smartphone-based 6-minute walk test (6MWT). Perceived activity was compared with sensor-measured activity and actual activity (sensor-measured with supplemented self-reported unrecorded activity). Multivariable linear regression assessed associations between activity and 6MWT performance and between activity and life satisfaction. Perceived cardiovascular risk was compared with the difference between heart age and actual age.

Results:

Of 518 enrolled participants (median age 58 years; 72% female), 93% shared data beyond demographics. Median engagement duration was 27 days, and 58% completed at least one full consecutive week of motion tracking. Perceived activity weakly correlated with both sensor-measured activity (ρ = 0.15, P = .01) and with actual activity (ρ = 0.15, P = .01). Median perceived activity was 3.5 hours/week, significantly higher than sensor-measured activity (0.9 hours/week; mean difference 2.9 hours, 95% CI 2.2–3.7; P < .001). In contrast, median actual activity was 3.2 hours/week and did not differ significantly from perceived activity (mean difference 0.7 hours, 95% CI −0.2 to 1.6; P = .11), indicating no significant over- or underestimation when unrecorded activity was accounted for. Sensor-measured physical activity was associated with longer 6MWT distance (+10.1 m per hour; 95% CI 3.9-16.4, P = 0.002). No association was observed between sensor-measured activity and life satisfaction. Perceived cardiovascular risk correlated with the difference between heart age and actual age (ρ = 0.41; P < 0.001).

Conclusions:

Smartphone-based cardiovascular monitoring is feasible in a European adult population and yields valid functional correlates of physical activity. However, incomplete phone carriage substantially limits sensor-only activity estimates, underscoring the need for hybrid measurement strategies. These findings support the use of smartphone platforms for scalable cardiovascular research, while highlighting persistent challenges in engagement and measurement completeness.