Beyond Atrial Fibrillation: Emerging Clinical Applications of Photoplethysmography in Consumer Wearables

Introduction: Photoplethysmography (PPG) is an optical sensing technology embedded in many current consumer smartwatches and smart rings. Long used for heart-rate monitoring and pulse oximetry, PPG has more recently become the foundation for population-scale screening for atrial fibrillation. The clinical applications of PPG now extend well beyond rhythm monitoring. Method: A narrative literature review of English-language publications indexed in PubMed, Europe PMC, IEEE Xplore, and Google Scholar between January 2020 and May 2026 was conducted, using combinations of the search term photoplethysmography with application-specific search terms. Earlier foundational publications were included selectively where necessary. Discussion: Current evidence most strongly supports consumer-wearable PPG for resting heart-rate estimation and for atrial-fibrillation notification pathways with adjudicated electrocardiographic confirmation. SpO2 trending is conditionally supported in healthy, normoxaemic adults but is insufficient for clinical decision-making during desaturation, motion, low perfusion, or in populations under-represented in validation datasets. Cuffless blood-pressure estimation, heart-rate variability, sleep staging, and obstructive sleep apnoea screening show device-, context-, and reference-standard-dependent reliability. Non-invasive blood-glucose monitoring through smartwatches or smart rings should not be used for diabetes management and is the subject of an explicit FDA safety communication. Conclusion: Consumer-wearable PPG is a multifunctional clinical sensing platform whose evidence maturity differs sharply by application. Responsible deployment requires awareness of signal quality, motion artefact, skin-tone bias, regulatory authorisation status, and local validation, particularly in the Indonesian primary-care context.