Cold water immersion (CWI) is a growing health and wellness trend. People have used ice baths and cold showers for generations. Modern culture now promotes them as performance therapy and self-care.
A new study in PLoS One reviewed the effects of CWI. The study found that CWI reduces inflammation and stress for a short time. It also boosts immunity, sleep quality, and overall well-being.
How Did the Researchers Choose Studies for Their Analysis?
Researchers searched ten databases, including MEDLINE, Cochrane, and PsycINFO. The search covered all studies published before January 17, 2024.
Two independent reviewers screened titles, abstracts, and full texts. A third reviewer resolved any disagreements.
Included studies had to meet these requirements:
- Healthy adults aged 18 or older.
- Acute or long-term exposure to CWI.
- CWI via cold shower, ice bath, or cold plunge.
- Water temperature at or below 15°C.
- Minimum exposure time of 30 seconds.
- Immersion at or above chest level.
- Reported outcomes related to sleep, stress, immunity, or mental well-being.
- Randomized controlled trials (RCTs) published in peer-reviewed journals.
Researchers excluded studies if they:
- Included trained athletes competing at a national level or higher.
- Involved participants with chronic illness or musculoskeletal injuries.
- Used cryotherapy chambers or accidental cold exposure.
- Allowed participants to wear protective garments.
Which Studies Were Selected for the Meta-Analysis on CWI?
Researchers identified 3,481 studies in the database search. Of these, they reviewed 109 in full. A total of 98 studies were not suitable—70 did not meet the inclusion criteria, and 28 did not fit the study design. Eleven studies comprised the final analysis.
The included studies have publication dates between 2014 and 2023. They were conducted in Australia, Lithuania, the Netherlands, Switzerland, Japan, the United States, and Finland.
A total of 3,177 participants contributed data to the analysis. Of these, 55.4% were female, but one study accounted for almost all female participants. The remaining studies included only male participants.
Most studies used cold water immersion in a bath. One study used cold showers.
Water temperature ranged from 7°C to 15°C. Exposure time varied from 30 seconds to two hours. Most studies compared CWI to seated rest or no immersion.
What Were the Health Effects of Cold Water Immersion?
Key findings showed a rise in inflammation immediately after CWI. The effects persisted for one hour. This suggests an acute inflammatory response.
Stress levels dropped 12 hours post-CWI. However, no stress changes occurred at other time benchmarks.
CWI did not improve immune function in the short term. Still, one study showed a 29% drop in sickness absence after 30 days of cold showers. Sleep and quality of life improved, but no mood changes ensued.
Additionally, CWI triggers an immediate “cold shock” response. This activates the nervous system, raising blood pressure and norepinephrine levels. Interestingly, stress markers decrease 12 hours later. This shift from stress to relaxation may demonstrate nervous system adaptation from CWI.
CWI improved quality of life in the shower study. Even so, its long-term impact remains unclear. The Wim Hof Method, which includes cold exposure and breathing exercises, has shown similar benefits.
Conclusion
Tara Cain, the study’s lead researcher from the University of South Australia, told Passport Health that CWI may have benefits, but it also comes with risks. “Cold water immersion could be beneficial for reducing stress and improving the quality of life among healthy populations,” she said. “However, people with pre-existing health conditions should be cautious, as the initial inflammatory response could have unintended effects.”
Research on CWI is still limited, and Cain urges caution. “Right now, there’s not enough high-quality research to say who benefits most or the best way to do cold-water immersion,” Cain said. “In the future, I expect we’ll see more long-term studies with diverse populations to better understand its lasting effects and real-world applications.”
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Logan Hamilton is a health and wellness freelance writer for hire. He’s passionate about crafting crystal-clear, captivating, and credible content that elevates brands and establishes trust. When not writing, Logan can be found hiking, sticking his nose in bizarre books, or playing drums in a local rock band. Find him at loganjameshamilton.com.
