Fatigue, elevated Heart Rate and Reduced Activity Levels may predict Long COVID, reports smartwatch data

A new study published in the journals of Npj Digital Medicine analyzed smartwatch data to identify pre-infection physiological markers associated with the development of long COVID. This study found that individuals who later experienced persistent symptoms, such as fatigue and shortness of breath, had higher resting heart rates and lower daily step counts at least three weeks before contracting SARS-CoV-2.

Specifically, these individuals took approximately 3,030 fewer steps per day and had a resting heart rate 2.37 beats per minute higher than those who recovered without lingering effects. These findings suggest that lower pre-infection fitness levels or existing health conditions may increase the risk of developing long COVID.

The long-term effects of SARS-CoV-2 infections on an individual's health are varied. According to the WHO, a post-COVID-19 condition (PCC) is when symptoms persist after at least two months without any other reason, or when new symptoms appear three months after the first SARS-CoV-2 infection. Due to the growing illness load, PCC, a multi-systemic condition2, has raised health care demand.

By giving objective measurements of heart rate, physical activity, step count, and sleep duration, data from wearable devices, like smartwatches or fitness trackers, offer a fresh perspective on the long-term effects of SARS-CoV-2. Thus, to analyze potential interactions with pre-existing health issues before to infection, during the course of infection, and during the post-infection phases, this study intended to examine resting heart rate, step count, subjective symptoms report, and self-reported quality of life.

This study used a wearable-derived behavioral and physiological dataset (n = 20,815) to identify the patients who self-reported having shortness of breath and persistent exhaustion following SARS-CoV-2 infection. At least 3 weeks before SARS-CoV-2 infection, these people (n = 50) had lower daily step counts (mean 3030/2909 steps less) and higher resting heart rates (mean difference 2.37/1.49 bpm) than symptom-free COVID-19 positive (n = 150) and negative controls (n = 150).

Furthermore, even prior to infection, a substantial decline in mean quality of life (WHO-5, EQ-5D) was linked to chronic tiredness and dyspnea. This study demonstrated how ongoing symptoms following a SARS-CoV-2 infection may be linked to underlying medical issues or reduced fitness levels. Overall, these results also demonstrate how wearable technology may be used to monitor health trends and offer important information about the long-term effects of infectious diseases.

Source:

Ledebur, K., Wiedermann, M., Puta, C., Thurner, S., Klimek, P., & Brockmann, D. (2025). Wearable data reveals distinct characteristics of individuals with persistent symptoms after a SARS-CoV-2 infection. Npj Digital Medicine, 8(1), 167. https://doi.org/10.1038/s41746-025-01456-x