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The effect of cold showering on health and work: a randomized controlled trial
Pragmatic Netherlands RCT (≈3,018 adults) randomizing 30 s, 60 s, or 90 s cold water at the end of usual hot showers vs control for 30 days: pooled intervention arms reported about 29% lower self-reported sickness absence from work than controls, without parallel differences in illness-day scores.
Why this matters
Large-field cold shower RCT (not ice-bath immersion) tied to workplace absence reporting.
Design highlights
- Groups: 30 s, 60 s, 90 s cold vs usual shower only
- Core adherence window: 30 consecutive days, then optional continuation
- Primary readout: self-reported sickness absence
Key result
Pooled cold exposure arms vs control: IRR ≈ 0.71 for absence rate (~29% relative reduction in the published primary analysis).
Nuance
Effects concentrated on absence reporting; illness-day metrics did not separate as clearly. Useful anchor for shower-length protocols; compare with cold water immersion evidence under the cold-plunge entry.
Outcomes
- otherPooled daily cold-shower arms: ~29% lower self-reported sickness absence vs control (IRR ≈ 0.71, statistically significant in trial report).
- otherIllness symptom / illness-day outcomes did not mirror the absence signal in the same analysis.