Rhonda P. Patrick, Teresa L. Johnson
FoundMyFitness, LLC, PO Box 99785, San Diego, CA 92169, USA, TLJ Communications, LLC, 36 Creek Harbour Blvd., Freeport, FL 32439, USA.
Sauna use, sometimes referred to as “sauna bathing,” is characterized by short-term passive exposure to high temperatures, typically ranging from 45 ◦C to 100 ◦C (113 ◦F to 212 ◦F), depending on modality. This exposure elicits mild hyperthermia, inducing a thermoregulatory response involving neuroendocrine, cardiovascular, and cytoprotective mechanisms that work in a synergistic fashion in an attempt to maintain homeostasis. Repeated sauna use acclimates the body to heat and optimizes the body’s response to future exposures, likely due to the biological phenomenon known as hormesis. In recent decades, sauna bathing has emerged as a probable means to extend healthspan, based on compelling data from observational, interventional, and mechanistic studies. Of particular interest are the findings from large, prospective, population-based cohort studies of health outcomes among sauna users that identified strong dose-dependent links between sauna use and reduced morbidity and mortality. This review presents an overview of sauna practices; elucidates the body’s physiological response to heat stress and the molecular mechanisms that drive the response; enumerates the myriad health benefits associated with sauna use; and describes sauna use concerns.
The evolving field of aging research has undergone dramatic shifts in recent decades, as the prevailing view of aging as a non-modifiable inevitability has given way to the possibilities of extending lifespan and, even more promising, healthspan. A widely accepted definition of healthspan is the period of one’s life spent in good health, free from the chronic diseases and disabilities that commonly accompany aging (Kaeberlein, 2018). Healthspan extension compresses the time spent in ill health, shifting it to one’s later years. Sauna use has emerged as a probable means to increase lifespan and extend healthspan. Bathing oneself in heat for the purposes of purification, cleansing, and healing is an ancient practice, observed for thousands of years across many cultures. Variations of its use appear today in the banyas of Russia, the sweat lodges of the American Indians, and the saunas of Finland. Sauna use, sometimes referred to as “sauna bathing,” is characterized by short-term passive exposure to high temperatures, typically ranging from 45 ◦C to 100 ◦C (113 ◦F to 212 ◦F), depending on modality. This exposure elicits mild hyperthermia, an increase in the body’s core temperature that induces a thermoregulatory response involving neuroendocrine, cardiovascular, and cytoprotective mechanisms that participate in restoring homeostasis and conditioning the body for future stressors (Laukkanen et al., 2018a).