Cold showers cut sick days by 29 percent

Researchers at the Academic Medical Center in Amsterdam ran a randomized trial with 3,018 working adults, assigning them to take hot showers that ended with 30, 60, or 90 seconds of cold water, or no cold water at all.

Over the following 90 days, people in the cold-shower groups reported 29 percent fewer sick days than the control group, regardless of whether they showered cold for 30, 60, or 90 seconds. The number of days people reported feeling ill did not differ between groups, only how many days they missed work.

That gap is curious: cold showers did not cut the days people felt ill, only more willing to show up anyway, or possibly just a little more resilient day to day. About 79 percent of people assigned to cold showers stuck with the habit for the full 30 days, and no serious side effects were reported, though the trial could not say which mechanism, physical or psychological, was driving the effect.

Fewer days off, same days feeling ill.