Only 37% in Trials Stuck With Daily Cold Showers
In A Nutshell
- Swiss adults who took mostly cold showers for 12 weeks reported 26% fewer sick days and 31% fewer days off work.
- Groups were sorted by actual shower habits, not random assignment, so the results show a link, not proof.
- Only 37% stuck with daily cold showers for all 12 weeks, and quitting was most likely in the first few weeks.
- Cold showers also avoided an estimated 8.8 metric tons of carbon dioxide across 586 participants.
Cranking the shower to cold every day sounds like a dare, not a health plan. Yet in a set of Swiss trials, people who took mostly cold showers over 12 weeks reported 26% fewer sick days and 31% fewer days off work than people who took cold showers less often. One catch: the comparison was built on what people really did in the shower, not on which group they were assigned to, so the results show a link, but they do not prove that cold water protects health.
Lena Glaser, a psychology researcher at the University of Basel, combined three trials in her doctoral dissertation. The health results come from a manuscript submitted to the Journal of Health Psychology, and the dissertation does not say whether other scientists have reviewed it yet.
Sick days were only part of Glaser’s goal. She used cold showers as a test case for a stubborn climate problem: getting people to keep up habits that help the planet but feel miserable. Heating water accounts for roughly 15% to 25% of home energy use in wealthy countries, according to the dissertation, and a cold shower skips that cost entirely.
Regular Cold Showers Tied to Fewer Sick Days in Swiss Trials
Three experiments ran in Switzerland between 2019 and 2024, with adults recruited through ads, social media and word of mouth. The final analysis covered 735 of them, and 719 of those had complete health data. Ages averaged about 26, and roughly two-thirds were women. People with conditions that cold water can make worse, such as severe heart disease or severe asthma, were left out.
Cold shower groups were told to turn the water to its coldest setting every day, for anywhere from 30 seconds to several minutes depending on the trial. Only one trial, with 166 people, assigned a group to keep showering as usual. The other two tested ways to help people stick with cold showers, so their warm group is mostly people who dropped the habit or never fully took it up. At the start and then monthly, participants reported online how many days they felt sick and how many they missed work.
Researchers then sorted people by what they actually did. Anyone who took cold showers at least 70% of the time counted as a cold shower user: 459 people, or 62.4% of the 735. The other 276 formed the warm group, though some of them took cold showers part of the time. People who stick with cold water may be tougher or healthier, which could explain part of the gap.
In everyday terms, that gap is small. Participants averaged about three sick days in the month before the trials began, so a 26% drop likely amounts to a day a month or less. Cold shower users also reported a small boost in well-being on a standard five-question survey, while physical well-being and skin health showed no clear difference.
One more caution: sick days and missed work came from participants’ memories, not medical records, and everyone knew which group they were in. Trial by trial, the drop in sick days was clear in only the largest of the three, and the drop in missed work in only one of the smaller two.
Quitting Cold Showers Is Most Likely in the First Few Weeks
A second analysis followed who quit and when, using two of the trials with 586 participants. Researchers counted someone as quitting after a full week with no cold showers. Only 37% stuck with daily cold showers for all 12 weeks. Quitting was most likely in the first few weeks, and women quit at a higher rate than men, with about a third more risk.
Four short mindset videos in one trial did no better than the comparison group. In the other trial, weekly video training meant to build confidence backfired: that group quit sooner, and only 14% took cold showers at least 70% of the time, compared with 47% of that trial’s comparison group.
Cold Showers Cut an Estimated 8.8 Metric Tons of Carbon Dioxide
Based on those same 586 participants’ own reports, the dissertation estimates that about 27,664 cold showers were taken, avoiding 8.8 metric tons of carbon dioxide from water heating, roughly what a car emits over 36,000 miles of driving. It rests on assumptions about shower length and water heating, not readings from household energy meters.
Another, untested part of the dissertation asks whether motivational interviewing, a counseling style used in addiction treatment that helps people talk themselves into change, could help with unpleasant but climate-friendly habits.
A payoff people can feel, even a small one, may sell a tough habit better than guilt does. Whether cold water deserves a spot in the health plan still needs a trial that assigns people to cold or warm showers and checks illness against medical records.
