Cold Showers Linked to 31 Percent Fewer Sick Days in Swiss Study

People who regularly took cold showers reported 31 percent fewer days off work because of illness than those who did not, according to a Swiss psychology study. ScienceAlert reported on the findings, which come from a pooled analysis of three randomized controlled trials involving 719 people.

The results are promising but early. They have not been peer-reviewed, they rely on what participants reported themselves, and the comparison groups were not formed by random assignment.

The key numbers from the cold shower study

• 719 people: the total across three randomized controlled trials, which researcher Lena Glaser analyzed together as part of her doctoral dissertation at the University of Basel in Switzerland.
• 31 percent: the reduction in days off work due to illness among regular cold-shower takers, compared with people who did not regularly take cold showers.
• 26 percent: the reduction in reported illness days in the cold shower group, compared with participants who mostly took warm showers.
• 70 percent: the share of the time participants stuck with the routine in the group that kept going. Among them, an average of 77.3 to 90 percent reported taking cold showers in any given week, depending on the trial.
• 29 percent: the drop in work absence due to illness found in a 2016 study, which echoes the new result. That earlier study did not see a reduction in days when people felt ill.

How the experiment worked

The cold shower work was part of a broader project on the psychological factors at play when people are urged to adopt new behaviors. Participants were asked to take cold showers, and they reported their habits, illness days and well-being during the experiment.

According to Glaser, many participants dropped out in the first two weeks, and dropout slowed after that. She said the high weekly rates among those who stayed suggest people gradually get used to the cold.

Participants in the cold shower group also reported slightly better psychological well-being on questionnaires. They reported signs of better physical well-being too, but that measurement was not statistically significant.

What the researchers say, and what limits the findings

In their preprint, which has been submitted to the Journal of Health Psychology, Glaser and her colleagues write that the pooled analysis shows a clear reduction in both illness days and sickness absence. They argue the improved well-being counters the concern that cold showers would make people feel worse. They also suggest the practice might improve mental and physical health, which could lower the risk factors behind sick leave.

ScienceAlert notes several caveats. The data are self-reported. Participants were grouped by how often they actually took cold showers, not at random, so other differences between the groups could play a role. The study also did not examine the biology behind any benefit.

A 2024 study found that people who took cold showers showed increased signals of immune response, and similar effects have been seen in research on cold water immersion. ScienceAlert says that could explain fewer sick days, but more research is needed to confirm it.

Why it matters for workers and employers

If later studies confirm and replicate the results, the researchers say cold showers could become a simple, low-cost workplace measure to support employees’ health and reduce absenteeism. For now, the findings are a signal worth testing rather than proof that cold showers prevent illness.

For readers curious about trying it, Glaser suggests starting slowly, lowering the temperature gradually and experimenting to stay comfortable. She said the water does not need to be equally cold every day, and that people should listen to their bodies.

What comes next

The preprint is under review at the Journal of Health Psychology. The full findings appear in Glaser’s dissertation, which is available on the University of Basel’s website. Independent replication would be needed before the result can be considered established.

Around Prague, based on reporting by ScienceAlert