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Fourth-year interns at Bastyr University are actively developing their clinical skills through treating patients at the school's clinic. They engage their didactic skills in rigorous case taking, examinations, evaluation, and a naturopathic-focused treatment plan under the supervision of their attending doctor. The interns are able to gain experience in areas such as mental health, mind-body medicine, oncology, hydrotherapy, physical medicine, out-reach community care, IV treatment, biofeedback, and so on. Each one of these opportunities presents a prime opportunity for the students to enrich their knowledge about conditions and approaches to care. In efforts to fortify their understanding, the students write case reports under the supervision of Dr. Baljit Khamba in their course "Advanced Case Studies." By completing these reports, future practitioners gain a valuable skill that they can then utilize once they graduate.
Background: Cardiovascular diseases (CVD) are the leading cause of death in the United States and are increasingly becoming more prevalent throughout the world. Although conventional treatments have reduced mortality in CVD patients, the quality of life (QOL) is not statistically significantly improved with these treatments.1 An overlooked cause of CVD is accumulation of heavy metals such as cadmium, lead, arsenic, and mercury.2-5
Methods: The author searched for studies on cardiovascular disease and sauna therapy, cardiovascular disease and cadmium toxicity, cardiovascular disease and lead, cardiovascular disease and arsenic, and cardiovascular disease and mercury toxicity using PubMed, ClinicalKey, and the Science Direct databases.
Results: The search methods used yielded three randomized controlled trials (RCTs) on congestive heart failure (CHF) and peripheral artery disease (PAD) that utilized sauna therapy concurrently with conventional treatment. Four studies were reviews on cadmium, arsenic, lead, and mercury toxicity and cardiovascular disease that revealed patients with CHF and cardiovascular diseases have higher levels of serum cadmium, lead, arsenic, and mercury than the general population. One review revealed the main mode of excretion of cadmium, arsenic, lead, and mercury is via sweat.
Conclusion: This review contains critically examined evidence for sauna therapy as related to heavy metal exposure in relation to CVD. The literature suggests that sauna therapy for three to six weeks can be an effective therapy for treating CVD and preventing complications of cardiovascular disease. Cadmium, lead, arsenic, and mercury toxicities are common in patients with cardiovascular disease because these non-essential toxic metals lead to endothelial dysfunction, reduced nitric oxide (NO) production, oxidative stress, and inflammation. Sauna therapy used in conjunction with conventional pharmaceutical therapeutics has been shown to decrease the toxin-load and improve the adverse effects of heavy metal accumulation leading to improvement in cardiovascular disease.
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About 25% of Americans die of cardiovascular diseases (CVD) every year. Heart failure is responsible for 11 million physician visits each year and more hospitalizations than all forms of cancer combined (CDC, 2013). High blood pressure, high cholesterol, and smoking are all risk factors of cardiovascular diseases. Diseases that are considered cardiovascular diseases include but are not limited to hypertension, pulmonary hypertension, chronic heart failure, coronary artery disease, peripheral artery disease, atrial fibrillation, aortic aneurysm, cardiomyopathy, myocardial infarcts, hypercholesterolemia, and stroke. Thirty percent of patients with acute heart failure are rehospitalized within 60-90 days.6 Given the scope of this problem, it would be of great benefit to widen our array of interventions to aid this large population of people.
Cadmium, lead, and arsenic are toxic metals that are non-essential to human existence. Cadmium has been shown to be associated with increased risk of renal dysfunction, osteoporosis, cancer, and cardiovascular diseases. There is an increased level of cadmium in smokers because tobacco accumulates cadmium from soil.2 Lead is a toxic metal that is still ubiquitous in our world today. Lead accumulation has been shown to be associated with an increased risk of elevated systolic blood pressure, coronary heart disease (CHD), stroke, and PAD.4 Inorganic arsenic is a naturally occurring toxic metal that can be found in chicken, rice, and groundwater. In epidemiologic studies, high-chronic arsenic exposure has been linked to CVD, including CHD, stroke, and PAD.3
Many toxic metals, including cadmium, lead, arsenic, and mercury, are excreted via sweat. Circulation can be enhanced by increasing the thermal load on the body allowing sweating to occur.7 Waon therapy (WT), a form of sauna therapy that translates to soothing warmth in Japanese, is a far infrared-ray dry sauna. WT is where the entire body is warmed in an evenly heated chamber for 15 min at a temperature that soothes mind and body, allowing the body temperature to increase 1.0-1.2 °C. Following the heated chamber, soothing warmth is sustained by maintaining warmth at rest for an additional 30 min. Fluids are supplied at the end to replace loss from perspiration.1 Another method of sauna therapy researched for patients with CHF included 10 far-infrared (FIR) sauna sessions over 14 days for 15 minutes at 60 °C followed by 30 minutes of bed rest covered by a blanket.8
This literature review will discuss the potential therapeutic benefits of sauna therapy for patients with CVD due to heavy metal exposure.
PubMed, ClinicalKey, and Science Direct were the databases utilized for this search with no restriction on date, type of study, nationality, or language. The initial search terms included "cardiovascular disease AND sauna." The following search terms included "cadmium in sweat," "cadmium and cardiovascular disease," "lead and cardiovascular disease," "heavy metals in sweat," and "arsenic and cardiovascular disease." These items were searched due to the relevance of this review having to do with heavy metal exposure in relation to CVD and diminishing risk with sauna therapy. The resulting 30 studies were narrowed down to 17 by language, availability, and relevance.
Six of the articles found in the search were systematic reviews of previous studies. Five of the articles included studies done with patients with CHF, two of the articles were about studies done on PAD, and one of the articles was on a study with patients with hypertension. Four of the articles were on cadmium, lead, arsenic, and mercury. One of the articles consisted of a case study. One article in this review disputes the hypothesis that toxic elements can be excreted via sweat. Two of the articles included mice in their studies and the rest were done on human subjects. The two articles found on mice studies were discarded for this review. All of the articles in this review were done on human subjects with CVD and included patients who were concurrently on conventional therapy and had been diagnosed with a cardiovascular condition by a physician.
Results on Heavy Metals and CVD
Borné et al discussed cadmium exposure and its effects on cardiovascular health leading to CHF and atrial fibrillation (AF). Blood samples were donated, and cadmium could be measured in 4378 people with conventional cardiovascular risk factors and biomarkers. Patients were followed from baseline examination between March 1991 and September 1996 in Malmö, Sweden until death, emigration from Sweden, or December 2010. Cadmium toxicity was found to be associated with CHF but not AF.2
One systematic review discussed lead exposure and its effects on CVD. This review included studies that used biomarkers to determine lead levels in blood, bone, or other specimens, environmental measures, or indirect measures such as living, job exposure, etc. Cardiovascular risk factors included those with reported clinical cardiovascular end points such as BP, CHD, stroke, or PAD and intermediate cardiovascular end points such as left ventricular mass, heart rate, heart rate variability, or electrocardiographic abnormality. In general populations, lead exposure was positively associated with clinical cardiovascular endpoints in all studies reviewed. In occupational populations, including those who work in battery, ceramic, pigment, and smelter industries, mortality was higher among workers with a greater number of years of employment. However, relative risk estimates across occupational studies varied widely, with positive, inverse, and null associations. This review found an association between lead exposure and blood pressure with populations in different geographic, ethnic, and socioeconomic backgrounds.4
One systematic review discussed arsenic exposure and its effects on CVD. Pooled relative CVD risk estimates were calculated separately for those with high levels of arsenic exposure. For CHD, stroke, and PAD, dose-response trends were evaluated in each study. Most studies were conducted in high arsenic exposure areas of Taiwan, Bangladesh, Chile, Inner Mongolia, and Pakistan. Most studies were assessed using indirect measures or using environmental measures. Most studies used CVD mortality endpoints to assess CVD outcomes. This review found an association between high arsenic exposure areas and CVD, CHD, PAD, and stroke.3
Sjögren et al discussed a case-controlled study involving mercury exposure and its effects on CVD. The case included a comprehensive study of 6784 male and 265 female workers from four mercury mines and mills in Spain, Slovenia, Italy, and Ukraine. Findings in Slovenia revealed increase in mortality due to ischemic heart disease among men. Duration of employment was positively correlated with mortality from ischemic heart disease.5
One systematic review discussed excretion of arsenic, cadmium, lead, and mercury via sweat. Studies included workers with occupational exposures and populations with no occupational exposures who were experiencing chronic ill health or were in good health. Arsenic was found to be higher in sweat than in blood plasma. Cadmium excretion was noted to be higher in sweat than in urine. Lead excretion was found to be higher in sweat than in urine. When measuring levels of mercury, sweat mercury levels varied; but there was no correlation with mercury urine levels.7
CVD and Sauna Therapy
Two of the articles found were randomized controlled trials (RCT) of patients with CHF.1,9 Fujita et al included 40 patients with symptomatic CHF, left ventricular ejection fraction (LVEF) <50% on echocardiography, and New York Heart Association (NYHA) functional classes II or III. Patients were split into two groups, one of which did sauna therapy once a day, five days a week, for four weeks. The populations assessed by the articles were adults (18+) diagnosed with either CHF and/or PAD with no significant differences in body weight, heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), cardiothoracic ratio (CTR), LVEF, BNP, and uric acid between groups. There was significant improvement in body weight, CTR, and BNP and echocardiography revealed an increase LVEF following four weeks of sauna therapy. These changes were not seen in the control group.9
Sobajima et al included 49 patients with previous hospitalization due to worsening of CHF, NYHA functional class ≧ II, or both. Patients were split into two groups, one of which completed sauna therapy once a day for three weeks. Results were based on evaluation of cardiac function and specific activity scale (SAS) which included brain natriuretic peptide (BNP), NYHA, and 6-minute walk distance (6MWD), flow-mediated vasodilation (FMD), natural killer (NK) cell activity, and SF-36 QOL scores. Sauna therapy improved NYHA functional class, SAS, and 6MWD, LVEF, NK cell activity, FMD, plasma BNP levels, and SF-QOL scores.1
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