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Cold water immersion (CWI) is a ‘hot topic’ at the moment. In many countries, there has been an explosion in the number of individuals undertaking CWI for anecdotally claimed mental and physical health-related benefits.1 These immersions range from static immersions in home-based ice baths and cold showers, to open water swims and dips. Associated with this, in 2021 Her Majesty’s Coastguard in the UK reported a 52% increase in call-outs associated with swimming and dipping and, between 2018 and 2021, there was a 79% increase in open-water swimming deaths (34–61 deaths) in the UK.2
For tropical animals such as humans, immersion in cold water is stressful and carries a significant risk of respiratory, cardiovascular and, possibly, peripheral neurovascular injury. The most dangerous response associated with CWI is ‘cold shock’.3 4 It is initiated by a rapid fall in skin temperature and includes gasping, hyperventilation, release of stress hormones, hypertension and arrhythmias. The loss of control of breathing can be a precursor to drowning, and the increased work required of the heart and circulation can result in cardiovascular pathologies. Cardiac arrhythmias are particularly common if cold immersion includes the face, breath holding and coactivation of the cold shock (sympathetic autonomic nervous system response) and diving response (parasympathetic autonomic nervous system response)—a combination of conflicting inputs to the heart termed ‘autonomic conflict’.4
We encourage people to enjoy the water, but in a responsible way that maximises the potential benefits and minimises the risks. With this in mind, we offer some guidance for those participating in CWI, those assessing …
Contributors MT initiated the project. All authors contributed sections, edited and approved the final submission.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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