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The Shinsato study revealed sauna therapy improvement in leg pain, exercise performance, ABPI, circulating CD34+ cell numbers, and serum nitrate and nitrite levels. There were no significant changes in VEGF.10 Shinsato et al's RCT included 21 patients with PAD. Inclusion criteria were intermittent claudication for a minimum of four weeks with no improvement with conventional treatment, resting ankle-brachial pressure index (ABPI) <0.75 in the affected limb on two consecutive examinations done weekly, and lower limb artery lesions detected with computed tomographic angiography (CTA, magnetic resonance angiography) or color duplex ultrasound. The patients were randomly divided into groups, one of which completed sauna therapy once a day, five days a week, for a total of six weeks. Results were based on evaluation of in leg pain, exercise performance, ABPI, circulating CD34+ cell numbers, serum nitrate and nitrite levels, and vascular endothelial growth factor (VEGF).10
There were very few adverse effects of sauna therapy and they were considered minor. In the Shinsato et al study, patients reported transient leg pain that subsided after a few sessions of sauna therapy.
The articles discussed in this literature review provide sufficient evidence to suggest sauna therapy in adjunct to conventional pharmaceutical therapeutics can be an effective form of treatment for reducing cardiovascular risk due to cadmium, lead, arsenic, and/or mercury exposure. This review provides some meaningful insights to guide future research and clinical practice. These articles reveal great promise in sauna therapy for the treatment and prevention of cardiovascular diseases such as CHF, PAD, high blood pressure, and stroke by reducing heavy metal accumulation.
Heavy metals such as cadmium, lead, arsenic, and mercury can have a significant physiologic effect. Cadmium increases the permeability of vascular endothelial monolayers by inhibiting cell proliferation and promoting cell death.11 It has also been shown to down-regulate nitric oxide (NO) mediated vasodilation.2 Lead accumulation has been shown to have an inverse relationship with estimated glomerular filtration rate (eGFR) indicating higher levels of lead can lead to reduced renal function. It has also been shown to enhance oxidative stress and impair NO-mediated vasodilation leading to increased vascular tone and peripheral vascular resistance.4 Arsenic exposure has been shown to increase inflammation, enhance oxidative stress, and endothelial and smooth muscle cell proliferation, vessel remodeling, and apoptosis.3 Mercury has been shown to increase endothelial dysfunction and reduce NO synthesis, increase oxidative stress and inflammation, and enhance mitochondrial and immune dysfunction.5 All of these mechanisms can lead to the progression of CVD.2-5
The renin angiotensin aldosterone system (RAAS) and natriuretic peptides (NPs) play key roles in the pathophysiology of CVD and CHF in particular. CHF progression leads to constant activation of the RAAS and a diminished response of NPs. This leads to increase in angiotensin II and aldosterone levels. This causes sodium reabsorption, which leads to hypertrophy and fibrosis in the heart and vasculature. Activation of the RAAS and NPs may be due to impaired NO-mediated vasodilation.
Many conventional therapies for CHF target the renin-angiotensin-aldosterone system (RAAS). Medications like angiotensin-converting enzyme inhibitors (ACEIs), angiotensin II receptor blockers (ARBs), and aldosterone-receptor blockers have significantly reduced mortality in CHF patients. Sauna therapy has been shown to enhance nitric oxide (NO) availability, decrease aldosterone, and decrease BNP and CNP activity.12 Due to these factors and the success of sauna therapy in the RCTs discussed in this review, it can be hypothesized that sauna therapy can be an effective form of treatment for CVD with concurrent use of conventional pharmaceutical therapeutics.12
Complications of Studies
Borne et al utilized a self-administered questionnaire on current use of conventional CVD medications, smoking habits, and educational status. This could lead to false information due to variability in patient's ability to remember their medications and willingness to reveal truthful information.2 The articles systematically reviewed in Navas-Acien et al did not sufficiently differentiate between classification of lead exposure and outcome and did not fully define what cardiovascular risk factors were and what other occupational exposures may have contributed to the findings.4 The articles systematically reviewed in Manuscript et al., 2013 did not include proper internal comparisons between high and low arsenic exposure.3 Both of these systematic reviews only included exact measurements of lead and arsenic levels within each individual for a few of the articles.3,11 Sjögren et al only discussed one case report on mercury exposure leading to the progression of CVD and therefore cannot be used as a sufficient source to prove this correlation.5
Shinsato et al's RCTs may have some semblance of a placebo effect due to the inability to create a double-blinded RCT considering the nature of the intervention.10 All of these RCTs were conducted in conjunction with conventional pharmaceutical therapeutics that were not standardized therefore outcomes could differ based on medications. No studies were conducted without the use of conventional pharmaceutical therapeutics, which may hinder the ability to understand the full efficacy of sauna therapy as an intervention.
Based on this discussion, the conclusion can be made that cadmium, lead, arsenic and/or mercury toxicity are among the factors that contribute to cardiovascular disease; and since it appears these heavy metals are predominantly excreted through sweat, sauna therapy can be effective in reducing the amount of heavy metals circulating in the bloodstream.7 More research would need to be conducted on heavy metal toxicant levels in patients before and after receiving sauna therapy to definitively make this claim.
Future studies should include research with larger populations with more specific age groups. Conventional therapies were taken simultaneously, and it would be interesting to see the effects of sauna therapy while decreasing the dose of conventional treatment to see if there can be therapeutic benefit without conventional treatment. Follow up on these studies were also short, and long-term effects would need to be monitored.
This therapy should be done concurrently with modifying lifestyle factors such as diet, exercise routine, and smoking cessation. The research was all done on patients who were concurrently using conventional treatment, and this must be taken into consideration as well.
There were no conflicts of interest reported in any of the articles in this review.
The studies found using these search methods indicate that sauna therapy may be an appropriate form of treatment for patients with CVD and in preventing CVD from advancing to complications such as CHF and PAD.
Cadmium, lead, arsenic, and mercury have been shown to depress nitric oxide (NO) availability, increase oxidation and inflammation, increase endothelial dysfunction, and induce cell death. These are all significant findings in CVD.2-5,7 These toxic metals can be excreted via sweat and therefore excessive sweating may help to reduce the amount of these metals circulating in the bloodstream.2,7
It is evident from the studies reviewed that 15 minutes of sauna therapy for at least five days a week for three to six weeks is able to reverse the adverse effects of heavy metal toxicity by enhancing nitric oxide (NO) availability, decreasing aldosterone, decreasing oxidation and inflammation, reducing endothelial dysfunction, and assisting with mitochondrial function.6,7,12 Considering heavy metal toxicity can play a role in the development of these conditions, it can be concluded that sauna therapy can help decrease levels of heavy metals such as cadmium, arsenic, lead, and mercury, and therefore improve prognosis of patients with cardiovascular diseases.
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This literature review was edited by Dr. Debrah Harding and Dr. Baljit Khamba.
1. Sobajima, M, et al. Waon Therapy Improves Quality of Life as Well as Cardiac Function and Exercise Capacity in Patients With Chronic Heart Failure. International Heart Journal. 2015;56(2): 203–208.
2. Borné Y, et al. Cadmium exposure and incidence of heart failure and atrial fibrillation: A population-based prospective cohort study. BMJ Open. 2015; 5(6): 1–8.
3. Manuscript, A., Exposure, A., & Review, S. (2013). NIH Public Access, 14(6), 542–555. http://doi.org/10.1007/s11883-012-0280-x.Arsenic
4. Navas-Acien A, et al. Lead exposure and cardiovascular disease - A systematic review. Environmental Health Perspectives. 2007; 115(3), 472–482.
5. Sjögren B, et al. Mortality from cardiovascular diseases and exposure to inorganic mercury. Occupational and Environmental Medicine. 2002; 59(7): 494.
6. Miyata M, Tei C. Waon Therapy for Cardiovascular Disease: Circulation Journal. 2010; 74(4), 617–621.
7. Sears ME, Kerr KJ, Bray RI. Arsenic, cadmium, lead, and mercury in sweat: A systematic review. Journal of Environmental and Public Health. 2012. http://doi.org/10.1155/2012/184745
8. Crinnion WJ. Sauna as a valuable clinical tool for cardiovascular, autoimmune, toxicant- induced and other chronic health problems. Alternative Medicine Review : A Journal of Clinical Therapeutic. 2011;16(3): 215–25.
9. Fujita S, et al. Effect of Waon Therapy on Oxidative Stress in Chronic Heart Failure. Circulation Journal. 2011; 75(2), 348–356.
10. Shinsato T, et al. Waon therapy mobilizes CD34+ cells and improves peripheral arterial disease. Journal of Cardiology. 2010;56(3), 361–366.
11. Manuscript, A., Exposure, C., & Disease, I. C. (2014). NIH Public Access, 24(3), 421–429. http://doi.org/10.1097/EDE.0b013e31828b0631.Cadmium
12. Fukushima A, Kinugawa S. Renin-Angiotensin-Aldosterone System and Natriuretic Peptides as Possible Targets of Waon Therapy in Heart Failure. Circulation Journal. 2017; 81(5), 635–636.
Dr. Hanisha Patel received a Bachelor of Science degree in pharmaceutical sciences at the Ohio State University. Following her undergraduate career, she worked for an NGO in Pune, India, where she worked with women in rural and slum areas. She then received her degree in naturopathic medicine from Bastyr University California where she continued to work with underserved communities locally and globally. As a naturopathic doctor, she specializes in cardiovascular diseases, diabetes, women's health, and neurodegenerative diseases. When she is not working with patients, she enjoys traveling, dancing, hiking, HIIT workouts, yoga, and watching sunsets.