Cold showers and sick days: 3,000 people, one winter
Three thousand Dutch adults were assigned to end their daily shower cold, or not. The cold-shower groups reported fewer sick days off work, but were ill just as often.
The short version
In winter 2015, 3,018 Dutch adults who did not take cold showers were randomly assigned to end their usual hot shower with 30, 60 or 90 seconds of cold water every day for a month, or to shower as normal. Over three months, the cold-shower groups reported fewer days off sick from work. But they reported just as many days of feeling ill. How long the cold lasted made no difference. Everyone knew which group they were in, and sick days were self-reported, so expectations may explain part of it.
Keep in mind
People knew their group and reported their own sick days, so expectation may explain part of the result. Days of illness did not change.
What they found
Of those in the cold-shower groups, 79% kept it up for all 30 days.
The cold-shower groups together reported fewer sick days off work than the control group: an incidence rate ratio of 0.71 (95% confidence interval 0.56 to 0.89). The median in every group was zero days, so most people took no sick days at all.
Days of illness did not differ. Neither did the result depend on 30, 60 or 90 seconds. The mental part of quality of life was very slightly higher, too little to matter, according to the authors. No serious side effects were reported.
What this means for your practice
Ending a shower cold did not make people ill less often. It went with fewer days off work, for reasons the trial cannot pin down.
This does not establish a cold-water routine to follow.
Methods and limitations
What the researchers did
Between January and March 2015, the researchers recruited 3,018 adults aged 18 to 65 in the Netherlands who had no serious illness and did not already take cold showers.
People were randomly assigned to four groups. Three ended their usual hot shower with cold water, about 10 to 12°C, for 30, 60 or 90 seconds, every day for 30 days, and then as they liked for 60 more. The fourth group showered as normal.
The main measures were days of illness and days off sick from work, reported by the participants. Quality of life, work engagement and anxiety were also measured.
How much can this tell us?
This is by far the largest randomized trial of cold water, and it was done in ordinary working adults, not athletes. That makes it more relevant than most.
But people were ill just as often. They took fewer days off, which could be a matter of feeling more energetic or of expectation. Participants could not be blinded, knew all four groups, and reported their own sick days.
It has not been repeated. A cold shower at home is close to what people do, but it is not the same as a plunge after a sauna.
What makes it useful
- Very large: 3,018 people
- Randomized, in ordinary working adults
- A simple, everyday form of cold
What limits it
- Not blinded, and sick days were self-reported
- Days of illness did not change
- One trial, one winter, one country
Where this study fits
Where this study fits
We score claims, not single studies. This one is part of the evidence for:
Cold showers mean fewer sick days. Some support
Low certaintyMedium effectIllness and death
Days off sick 29% fewer
Likely 11% to 44%
Fewer cases than the comparison group. The bar is the best estimate, the band behind it the likely range.
Cold water makes you feel better. Some support
Low certaintySmall effectHow you feel or perform
Read the original
Buijze GA, Sierevelt IN, van der Heijden BC, Dijkgraaf MG, Frings-Dresen MH. The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial. PLoS One. 2016;11(9):e0161749.
DOI 10.1371/journal.pone.0161749 · PubMed 27631616