Abstract
In South Korea, over half the adults are insufficiently active. Mobile health (mHealth) interventions can increase physical activity. This study evaluated the cost-effectiveness of a smartwatch and smartphone application to promote moderate-intensity physical activity among South Korean adults aged 45–64 years. A Markov cohort model with seven health states was developed to compare intervention and non-intervention scenarios. Transition probabilities, utility values, and costs in the model were calculated using data from the National Health Insurance Service and the Korea National Health and Nutrition Examination Survey. The intervention effect was measured through changes in moderate-intensity physical activity (≥ 150 min/week) over a 12-week prospective study (n = 304). The analyses used 10-year and lifetime horizons with comprehensive sensitivity. The intervention yielded an incremental gain of 0.0077 quality-adjusted life years (QALYs) at an additional cost of 6.3 USD/person, resulting in an incremental cost-effectiveness ratio (ICER) of 829 USD/QALY gained over 10 years. Benefits were greater in the 55–64 age group (455 USD/QALY) than in the 45–54 age group (1,595 USD/QALY). Probabilistic sensitivity analysis confirmed robust cost-effectiveness at a willingness-to-pay threshold of USD 20,000/QALY. The program using smartwatches and smartphones was cost-effective for middle-aged South Korean adults, particularly those aged 55–64 years. These findings support integrating mHealth solutions into national physical activity promotion strategies as an economically feasible approach to addressing physical inactivity and preventing chronic diseases in aging populations. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10916-025-02291-z.