Laboratory comparison of consumer-grade and research-established wearables for in field research in sub-Saharan Africa

Stefan Mendt ^1* Georgi Zout ¹ Marco Rabuffetti ² Hanns-Christian Gunga ¹ Aditi Bunker ³ Sandra Barteit ³ Martina Anna Maggioni ¹

• ¹ Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Institute of Physiology, Center for Space Medicine and Extreme Environments Berlin, Berlin, Germany
• ² IRCCS Fondazione Don Carlo Gnocchi, Milano, Italy
• ³ Heidelberg Institute of Global Health, Heidelberg University Hospital, Heidelberg University, Heidelberg, Germany

Background: Consumer-grade wearables are becoming increasingly popular in research and in clinical contexts. These technologies hold significant promise for advancing digital medicine and remote monitoring, and they offer great potential for use in remote and rural areas in low-income settings. This study evaluates the data agreement between consumer-grade and research-established devices under standardized conditions. Methods: Twenty-two participants (11 women, 11 men) performed a structured protocol, consisting of six different activity phases (sitting, standing, and the first four stages of the classic Bruce treadmill test). We collected heart rate, (core) body temperature, step count, and energy expenditure. Each variable was simultaneously tracked by consumer-grade and established research-grade devices. Differences were statistically tested and validity was determined using Pearson's correlation r, Lin's concordance correlation coefficient (LCCC), Bland-Altman method, and mean absolute percentage error. Results: A good agreement was found between the wrist-worn Withings Pulse HR (consumer-grade) and the chest-worn Faros Bittium 180 in measuring heart rate while sitting, standing, and slow walking on a treadmill at a speed of 2.7 km/h (LCCC≥0.76, |bias|≤3.1 bpm), but this decreased with increasing speed (LCCC≤0.29, |bias|≤11.7 bpm). The agreement between the Withing device and the research-established device worn on the wrist (GENEActiv) for measuring the number of steps also decreased during the treadmill phases (first stage: LCCC=0.35, bias=0.6 steps/min; fourth stage: LCCC=0.11, bias=17.3 steps/min). Energy expenditure agreement between the Withings device and the indirect calorimetry method was poor during the treadmill test (|LCCC|≤0.07, |bias|≥1.7 MET). The Tucky thermometer under the armpit (consumer-grade) and the Tcore sensor on the forehead were found to be in poor agreement in measuring (core) body temperature during resting phases (LCCC≤0.22, |bias|≥0.8°C) and deteriorated during the treadmill test.The Withings device showed adequate performance for heart rate at low activity levels and step count at higher activity levels, but had limited overall accuracy. The Tucky device showed poor agreement with the Tcore in all six different activity phases. While these consumer-grade wearables may not be suitable for controlled research environments, the Withings device could be useful to capture general physiological trends, for example, for long-term field monitoring or population-health surveillance.