Oleg Stanislavovich Glazachev, Ahamad Salehi, Maxim Andreevich Zapara, Elena Nikolaevna Dudnik, Vlada Germanovna Samartseva, Davide Susta.
IM Sechenov Medical University, Physiology Department, Trubetskaya str, 8, bld.2, 119992, Moscow, Russia.
Dublin City University, School of Health and Human Performance, Glasnevin Campus, Dublin, Ireland.
Wu Tsai Neurosciences Institute, Stanford Neurosciences Building, 290 Jane Stanford Way, Rm E152, Stanford, CA, USA
Context: Hyperthermia is known to be beneficial to patients affected by various diseases. Brain Derived Neurotrophic Factor (BDNF) is a marker of neuroplasticity usually increased as response to acute exposure to human body stressors. Little is known about BDNF changes after repeated exposure to hyperthermia.
Objective: To investigate the effect of a repeated hyperthermia exposure program (HTC) on serum BDNF in healthy humans. Design, setting, participants: Randomized, single-blind, controlled trial in healthy humans conducted at Sechenov University Physiology Laboratory between December 2016 and November 2018. The treatment period was 10 weeks. Researchers analyZing serum BDNF and questionnaires data were blinded to participants allocation.
Participants: Were 34 healthy male (age 20.2 +- 1.6 years).
Intervention: Repeated Hyperthermia exposure program, HTC, versus Light Intermittent Exercise, LIE, program as control (10 weeks). Main outcome measure: Change in BDNF from baseline to final visit three days after treatment completion.
Results: 25 participants were analyzed. One participant withdrew before signing the informed consent and 8 participants (n 1⁄4 3 in HTC and n 1⁄4 5 in LIE) could not undertake the first assessment and were excluded. Mean change in BDNF was higher in HTC group vs LIE after both time points (after 12 and after 24 sessions). After 24 sessions BDNF was 30170 (SD 5268) pg/ml in HTC group a value that was significantly higher than 24104 (SD 2876) pg/ml measured in LIE group. BDNF concentrations were significantly higher than baseline values in HTC group only, 30170 (SD 5268) vs 26710 (SD 5437) pg/ml.
Conclusion: A 10-week program consisting of repeated exposure to hyperthermia resulted in a significantly higher increase of circulating BDNF compared to a program consisting of intermittent light intensity exercise.
Hyperthermic conditioning consists of repeatedly exposing the human body to high temperature for a short amount of time. This practice has been used in many parts of the world in different forms such as steam saunas, dry saunas, hot water immersion, Waon . The potential therapeutic use of these practices (Laukkanen et al., 2016) are based on the human body response to hyperthermia as physiological stressor and on the resulting adaptations to hyperthermia: increased resistance to thermal stressors, increased bronchial conductivity and pulmonary ventilation, sweating, activation of neuro-hormonal and cardiovascular systems, improved microcirculation (Katz et al 2006). For example, Waon is a japanese technique based on infrared light exposure (dry sauna) which consists of exposing the entire human body to high temperature (60˚C) for 15 min, so that the core temperature increases by approximately 1.2˚C. This form of hyperthermic conditioning has been shown to improve hemodynamics and symptoms in Chronic Heart Failure patients (Tei 1995, Tei 1996; Kihara 2002, Kihara et al., 2004).