Adults who regularly dialed down their shower temperature over a 12-week period reported missing 31 percent fewer workdays due to illness and experiencing 26 percent fewer days feeling unwell, according to a series of trials analyzed by researchers at the University of Basel.
Swiss Trials Track 719 Participants Over 12 Weeks
The research examined data from 719 healthy adult participants with an average age of 26. The research was conducted in Switzerland between 2019 and 2024 and detailed in Lena Glaser’s doctoral dissertation at the University of Basel. Approximately two-thirds of the participants were women. People suffering from ailments aggravated by cold water—such as severe asthma or advanced heart disease—were excluded from participation. Participants had no history of asthma or significant heart problems and were not regular cold-shower users.
Specifically, they were asked to take showers at the coldest temperature permitted by the equipment for 12 weeks. Participants in the cold-shower groups were instructed to turn their water to the coldest setting allowed by their plumbing for durations ranging from 30 seconds to several minutes daily. Depending on the specific trial, between 77.3 and 90 percent of those who stuck to that frequency reported having cold showers in any given week. Researchers subsequently categorized participants based on their actual behavior rather than random assignment, defining regular users as those who took cold showers at least 70 percent of the time.
Dropout rates peaked during the first two weeks of the experiments, leaving only 37 percent of participants completing the full 12-week regimen of daily cold showers. Maintaining the daily routine proved difficult for many enrollees. Many participants dropped out during the first two weeks, but the number of those leaving subsequently declined. That suggests people gradually get used to it,
Glaser said.
Cold Showers Reduce Absences and Improve Participant Well-Being
The findings align closely with a 2016 study, which similarly recorded a 29 percent reduction in work absences among participants taking 30-, 60-, or 90-second cold showers for 90 days. Beyond attendance metrics, the Swiss participants reported feeling more alert and refreshed after showering. Participants taking cold showers reported improvements in physical and mental well-being, including a sense of accomplishment from overcoming their initial reluctance to step into cold water.
Across the trials, participants recorded approximately 27,664 cold showers, which avoided an estimated 8.8 metric tons of carbon dioxide emissions. The investigation also tracked utility savings and emissions. Heating water accounts for roughly 15% to 25% of household energy use. Reducing the water temperature from 40 down to 15 degrees Celsius for a 45-litre shower results in a 1.3 kWh energy savings. Across the 12-week period, participants achieved an average reduction of 15 kilograms of CO₂ emissions per person, an amount equivalent to the emissions produced by driving an automobile a distance of 100 kilometres.
Cold Water Immersion Aids Recovery but Risks Cardiovascular Stress
Increasing circulation redistributes blood and delivers freshly oxygenated blood to areas of the body that need to recover,
said Dr. Sharon Hame, a UCLA Health orthopedic surgeon. Medical experts emphasize that cold-water immersion affects circulation and inflammation. It decreases the time it takes your muscles to recover after exercise.
Heart problems or certain other health issues, particularly when combined with abrupt contact with cold water, can bring on cardiovascular stress and rapid breathing. However, health professionals warn against sudden temperature drops for vulnerable individuals. Anyone with an underlying medical condition should consult a healthcare provider before starting a cold-shower routine. The sudden exposure to cold can spike blood pressure and heart rate, potentially leading to irregular heartbeat,
cautions the Cleveland Clinic. Physicians recommend that anyone with heart disease, circulatory issues, asthma, or cold-induced conditions consult a healthcare provider before altering their showering routine, matching the protocols of the 2016 study.