Sweat-Based Wearable Tracks Sleep Hormones Cortisol and Melatonin Continuously, Study Finds

In a sleep study, the standard way to learn what a person's hormones are doing overnight is to wake them up. Technicians rouse patients at intervals and collect saliva, because saliva is the gold-standard source for measuring cortisol and melatonin. Researchers at the University of Texas at Dallas, working with the Texas biotech company EnLiSense, have now shown a wearable sensor that reads both hormones from sweat instead, with no interruption required.

The device is an electrochemical sensor that tracks cortisol, which promotes wakefulness, and melatonin, which signals the body to sleep. It runs on EnLiSense's CORTI wearable platform, which the company is commercializing. The team published a proof-of-validation study in Biosensors and Bioelectronics: X. According to the researchers, it is the first to demonstrate the circadian rhythmicity of cortisol and melatonin measured through sweat. The sensor works on passive sweat, the kind the body produces naturally without exercise or other stimulation.

The study enrolled 43 participants, each of whom wore the sensor for 48 hours. During that time, researchers collected saliva samples 12 times to compare against the sensor's readings. The two methods produced similar results, which the researchers took as evidence of the sensor's accuracy.

Annapoorna Ramasubramanya, a biomedical engineering doctoral student, is the study's first author. She said that precise, continuous evaluation of both hormones is essential for understanding and managing circadian health, and that saliva sampling is inconvenient for continuous monitoring. Her part of the project was to translate the device's data into thresholds that can be used for stress, wellness and circadian rhythm monitoring. In September she received a New Investigator Award at the World Sleep Congress 2025 in Singapore, an event organized by the World Sleep Society, a nonprofit for sleep medicine and research professionals.

Dr. Shalini Prasad, the study's corresponding author, is a professor and head of bioengineering in the Erik Jonsson School of Engineering and Computer Science. She recruited Ramasubramanya into her Biomedical Microdevices and Nanotechnology Lab after the student impressed her in a Nanotechnology and Sensors class. Prasad said Ramasubramanya contextualized the chemistry behind the device's readings so that the information can be explained, answering questions the lab could not address before. She also said Ramasubramanya is very willing to take feedback.

The researchers point to a gap in the consumer market. Wearables now sold for sleep tracking estimate duration and stages from movement, heart rate and sometimes body temperature. They do not measure the hormones themselves. Prasad said CORTI adds to chronobiology, the study of the body's natural rhythms and cycles, by giving people objective data they could use to improve their sleep. She argued that ordinary exposure to electronics is changing sleep patterns, that people need not be shift workers or pilots to disrupt their circadian rhythms, and that mental health issues are also tied to sleep quality.

Ramasubramanya's route into circadian data analysis began with music. Originally from Bengaluru, India, she studied computer engineering as an undergraduate and has played the veena, an Indian stringed instrument similar to the sitar, in the Carnatic tradition for 16 years. That south Indian classical music builds melody and rhythm on ratios, divisions and patterns, and she applied the same mathematical principles in the study's analysis.

This remains a proof-of-validation study, and its commercial partner is the company selling the platform. What to watch is whether the sweat readings hold up beyond a 48-hour window and in settings like clinical sleep labs, where the technology could replace the nightly waking for saliva samples.