How to determine biological age and stress resistance using sweat analysis

Chronological age says little about the actual state of the body: two people of the same age can differ radically in terms of endurance, risks, and response to treatment. A team of ETH Zürich, Empa, Caltech, and the University Hospital of Basel is launching the AGE RESIST (AGE clock for RESIlience in SweaT) project: scientists want to learn how to accurately and easily assess biological age and “resilience” (resistance to stress and strain) based on molecules in sweat that are continuously collected by wearable sensors. The idea is to turn complex laboratory panels into a convenient “age clock” on the skin to personalize medical decisions and reduce the side effects of treatment. The project is funded by the Swiss National Science Foundation (SNSF).

Background of the study

Calendar (chronological) age is a poor predictor of the actual state of the body - endurance, vulnerability to disease and tolerance of treatment. That is why biological age "clocks" have been rapidly developing in recent years. But many of them rely on expensive laboratory panels (blood, "omics"), give results episodically and have not always proven clinical added value. Against this background, the AGE RESIST project (ETH Zürich, Empa, Caltech, University Hospital Basel) offers a different way: to search for new biomarkers in sweat and read them continuously with wearable sensors to assess not only "age" but also resilience - resistance to stress and recovery rate. This "clock" approach is conceived as a tool for personalizing therapy: to select the intensity of interventions for the actual physical condition of the patient and thereby reduce side effects. The project is funded by the Swiss National Science Foundation (SNSF).

Why sweat? It provides a convenient window into physiology: electrolytes, metabolites, stress and inflammation markers that can be measured without needles and in real time. Skin-interface platforms have advanced dramatically in recent years, with flexible electrochemical patches, microfluidic collectors, and multi-hour sensors capable of tracking analyte dynamics, not just static values. This is important for resilience: it is not so much absolute concentrations that are predicted, but the profile of the response to heat/load and the shape of the “recovery curve” in conjunction with heart rate, respiration, and core temperature.

At AGE RESIST, this idea is being put into practice: the team is developing a portable sweat sensor, testing prototypes in a climate chamber, and combining molecular signals with physiology (heart rate, respiratory rate, core temperature, etc.) to train an age+resilience model. The project is led by Noé Brasier (ETH Zürich); on the Empa side, Simon Annaheim is in charge of the sensorics department. The expected outcome is a convenient “age scale” for the clinic, helping to plan treatment and rehabilitation based on physiological age rather than passport age.

The context is broader than one project: classic “clocks” - epigenetic, transcriptomic, proteomic - are developing rapidly, but in 2024-2025 their limitations and “recalibration” (dependence on the composition of blood cells, reconfiguration of models for different populations, portability to the clinic) are being actively discussed. The idea of sweat/wearable “clocks”, first systematically proposed in the academic agenda back in 2023, just closes the gap between laboratory biomarkers and everyday monitoring: it seeks to capture the dynamic side of aging - the system's ability to respond to a challenge and recover.

How it will work

The researchers are developing a portable sweat sensor that simultaneously reads new molecular biomarkers and combines them with physiological parameters (heart rate, respiratory rate, core temperature, etc.). According to Simon Annaheim from the Biomimetic Membranes and Textiles (Empa) laboratory, the precision of the skin sensors allows for continuous, reliable data on the body's state. The team is testing prototypes in a climate chamber where heat and load can be dosed. Based on these data streams, a "clockwork" algorithm will be trained that links the ability to cope with load and recover with biological age and resilience.

Who is behind the project and what will it change?

The initiator is Dr. Noé Brazier (ETH Zürich, Institute of Translational Medicine); the project involves clinical, sensory and material specialists from ETH, Empa, Caltech and Basel hospitals. If the “watch” demonstrates reproducibility and predictive value, it can be used to select the intensity of therapy and rehabilitation based on “physiological” age, rather than a passport - from oncology and cardiology to orthopedics and geriatrics. Ideally, this reduces “overtreatment”, side effects and missed chances for timely interventions.

Recruiting Volunteers: What Participants Will Experience

Recruitment for a pilot study is currently underway. They are looking for men and women willing to complete ~1 hour of exercise, in the age range of 44-54 or 60-70 years, with a BMI < 30 and fluency in German or English. Participation will cost: physical fitness assessment (spiroergometry), biological age assessment, blood test results and compensation of 200 CHF (including travel expenses). The study site is Empa, St. Gallen. The procedure includes three visits (~6 hours in total): screening; the main visit with cycling exercise at gentle heating and pauses (sweat is taken, while parameters are recorded with non-invasive sensors); a final short visit to check the removal of the sensor capsule for monitoring the temperature of the "core". The data is confidential; no medical benefit is promised to the participants.

Why sweat?

Sweat is a "window" into metabolism: it contains electrolytes, metabolites, inflammation and stress markers, which can be measured continuously and without needles. Unlike episodic blood tests, sweat from wearable sensors provides dynamics - how the body reacts to a stimulus (heat, load) and how quickly it recovers. For an "age watch", it is not only "how many" molecules at a time that are important, but also the response profile: the amplitude, speed and shape of the recovery curve. In conjunction with heart rate, respiration and core temperature, this turns into a digital "portrait" of resilience - the key to personalized treatment.

What exactly is measured and how is it interpreted?

In the pilot, the team compares:

• Molecules in sweat: a new set of candidate biomarkers of biological age and stress response.
• Physiology: Heart rate, respiration, core temperature (via swallowed sensory capsule), skin parameters.
• Endurance and “heat resistance”: thermally controlled cycling and recovery.
  The data are then glued together into an age-resistance model that is validated across age groups and repeats. The goal is a tool with clinical added value that is easy to use and understand for clinicians.

Where this can come in handy tomorrow

• Intervention planning. Assessing the “physiological” age and reserve before surgery or intensive care to more accurately dose the risk.
• Rehabilitation and sports medicine. Monitor resilience over time, adjust loads in time and monitor overload.
• Geriatrics and Chronic Diseases: Identify 'gaps' in resilience long before clinical events and personalize treatment.

Briefly - the main thing

• AGE RESIST looks for biomarkers of biological age and resilience in sweat and trains wearable sensors to “read” them continuously.
• The project is led by ETH Zürich, Empa, Caltech and the Basel Clinics, and is financed by the SNSF. The goal is an age-specific "clock" for personalized medicine.
• In the pilot - 3 visits, cycling load at soft heat, sensory capsule for core temperature, compensation 200 CHF.

Source: Empa's page about the AGE RESIST project.