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Can smartphones or smartwatches help detect early signs of neurological or mental illness? Researchers at the University of Geneva (UNIGE) monitored a group of participants wearing connected devices, and used artificial intelligence to analyse data such as heart rate, physical activity, sleep and air pollution. Their findings show that connected devices can accurately predict emotional and cognitive fluctuations, opening new avenues for the early detection of changes in brain health. The study has been published in npj Digital Medicine.
Brain health, encompassing both cognitive and emotional functions, is one of the major public health challenges of the 21st century. According to the World Health Organization (WHO), more than one in three people worldwide live with neurological disorders such as stroke, epilepsy or Parkinson’s disease, while more than one in two individuals will experience a mental disorder – including depression, anxiety disorders or schizophrenia – at some point in their lives. As populations age, these figures continue to rise.
Even in healthy adults, brain health fluctuates over time, reflecting interactions between multiple factors, including environmental influences and individual lifestyle habits. Analysing day-to-day or week-to-week changes in cognitive and emotional functioning is therefore essential to enable proactive and individualised prevention strategies.
A team at the University of Geneva (UNIGE) set out to determine whether wearable and mobile technologies could be used to monitor brain health continuously and non-invasively. To this end, 88 volunteers aged between 45 and 77 were equipped with a dedicated smartphone app and a smartwatch. Over a ten-month period, these devices collected “passive” data – without any intervention or change in participants’ daily habits – including heart rate, physical activity, sleep patterns, as well as weather conditions and air pollution levels. In total, 21 indicators were analysed.
Every three months, participants also provided “active” data by completing questionnaires on their emotional state and undergoing cognitive performance tests.
AI-analysed data
Once data collection was complete, the passive data were analysed using artificial intelligence developed as part of the project. “The aim was to determine whether AI could predict fluctuations in participants’ cognitive and emotional health based on these data,” explains Igor Matias, a doctoral assistant at the Research Institute for Statistics and Information Science at the Geneva School of Economics and Management (GSEM) at UNIGE and lead author of the study.
The AI-based predictions were then compared with the results of the questionnaires and tests. “On average, the error rate was just 12.5%, opening up new possibilities for the use of connected devices in the early detection of abnormalities or changes in brain health,” the researcher adds.
Emotional states are the easiest to predict
Emotional states were the most accurately predicted by the artificial intelligence, with error rates ranging generally between 5% and 10%. Cognitive states, in contrast, were predicted less precisely, with error rates ranging from 10% to 20%. In other words, AI performs better at forecasting responses to emotional questionnaires than cognitive tests.
Regarding the relevance of passive indicators, air pollution, weather conditions, daily heart rate, and sleep variability emerged as the most informative factors for cognition. For emotional states, the most influential factors were primarily weather, sleep variability, and heart rate during sleep.
Reference: Matias I, Haas M, Daza EJ, et al. Digital biomarkers for brain health: passive and continuous assessment from wearable sensors. NPJ Digit Med. 2026;9(1):197. doi: 10.1038/s41746-026-02340-y
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