Hyperthermia, a state of elevated core body temperature, stresses the body, activating molecular mechanisms that mitigate protein damage and aggregation and promote endogenous antioxidant, repair, and degradation processes. Whole-body hyperthermia is a therapeutic strategy used to treat various medical conditions, including cancer, fibromyalgia, and others. Emerging evidence suggests that whole-body hyperthermia might be useful in treating depression.
While similar conceptually to recreational sauna use, whole-body hyperthermia may differ in that the nature of the duration and temperature of clinical interventions specifically targets levels of functional stress that drive key physiological responses, such as protein denaturation, alteration of cellular structures (such as the cytoskeleton and membranes), and changes in enzyme complexes needed for DNA synthesis and repair.
A whole-body hyperthermia device, the Heckel HT-3000 (shown above), has been used in some clinical trials.
Whole-body hyperthermia is typically administered in the clinical setting using a variety of modalities. Some of these include the use of hot-water blankets, warm-water baths, heating coils, or specialized lamps that emit infrared-A radiation in a confined area or chamber. The recipient typically is exposed to the heat source until their core body temperature reaches a desired (elevated) temperature, with a maximum of approximately 42°C (107°F) for a duration of 60 minutes or longer. The recipient's body temperature, heart rate, oxygen saturation, blood pressure, cardiac function, and respiration rate are closely monitored.
Preclinical and clinical studies have demonstrated beneficial effects of whole-body hyperthermia as an adjunct to conventional cancer therapies. A key mechanism associated with whole-body hyperthermia in cancer treatment exploits the tumor microenvironment. The blood vessels within tumors are often disorganized, resulting in areas within the tumor that are acidic or have low oxygen levels. Under these conditions, conventional radiation and chemotherapy treatments are less effective. Cancer cells are highly sensitive to heat treatment, however, and exposure to temperatures between 40°C and 44°C is cytotoxic while leaving healthy cells undamaged. Using hyperthermia in conjunction with radiation and chemotherapy has an additive effect, bolstering the effects of these therapies.
Some of the other mechanisms by which whole-body hyperthermia elicits its beneficial effects against cancer overlap those experienced during sauna use. For example, expression of heat shock proteins, which increases markedly following heat stress associated with sauna use, also increases in response to hyperthermia, especially in malignant cells, rendering them more susceptible to destruction by natural killer effector cells.
Fibromyalgia is a disorder characterized by widespread musculoskeletal pain, fatigue, altered sleep, memory, and mood. An intervention study involving 67 patients with fibromyalgia who received whole-body hyperthermia treatment either once or twice a week versus standard therapy for three weeks demonstrated that one treatment per week reduced the participants' pain and improved quality of life. Similar results were observed in a larger study involving 102 patients with severe, progressive fibromyalgia.
Compelling data suggest that whole-body hyperthermia may be useful in treating depression. In particular, in a randomized, double-blind study of 30 healthy adults diagnosed with depression, participants who were exposed to a single session of whole-body hyperthermia in which core body temperature was elevated to 38.5°C (101.3°F) experienced an acute antidepressant effect that was apparent within one week of treatment and persisted for six weeks after treatment.
Similarly, in a double-blind randomized controlled trial in which core body temperature was elevated by 1.5°C (2.7°F), participants' levels of IL-6, a pro-inflammatory protein, increased markedly, and participants with the highest IL-6 levels had the lowest levels of depression one week later [unpublished data]. Some of these benefits may be due to the effects of heat stress on circulating levels of pro-inflammatory IL-6 and the reciprocal effects of IL-10, an anti-inflammatory factor.
Whole-body hyperthermia increases core body temperature for an extended duration. Scientific evidence suggests that it may be useful in treating a variety of medical conditions, including cancer, fibromyalgia, and depression. Some of the mechanisms that drive the beneficial effects of whole-body hyperthermia are similar to those elicited by regular sauna use.