These novel results suggest that effective testosterone treatment that achieves normalization of testosterone levels - in other words, a high enough increase in testosterone levels - significantly decreases the incidence of atrial fibrillation.
Importance of adherence and achievement of effective (therapeutic) testosterone levels
This study is the first and largest to evaluate the association between testosterone treatment and the incidence of atrial fibrillation. It confirms previous reports that low testosterone levels are associated with increased incidence of atrial fibrillation. The largest and significant decrease in the incidence of atrial fibrillation was seen in the group receiving effective testosterone treatment. This underscores the importance of adherence to testosterone treatment in order to realize clinical benefits, which require achievement of a high enough elevation in testosterone levels.
The importance of providing effective testosterone treatment (achieving normalization of testosterone levels) was highlighted in a previous study which showed that it results in major and significant reduction of heart attack, stroke and all-cause mortality by 18%, 30% and 47%, respectively, compared to ineffective testosterone treatment (not achieving normalization of testosterone levels).13 We covered this study in a previous editorial “Adherence to testosterone therapy - short term treatment is not sufficient for achievement of maximal benefits”.
Contrary to what is commonly feared, testosterone treatment that effectively increases testosterone levels does not increase the risk of deep venous thrombosis or pulmonary embolism.14 The cardiovascular safety of testosterone treatment was recently confirmed in a new study published in the Journal of the American Medical Association (JAMA). This study investigated the association between testosterone treatment and cardiovascular outcomes in men with testosterone deficiency.15 The primary outcome was a composite of cardiovascular end points that included acute myocardial infarction, coronary revascularization, unstable angina, stroke, transient ischemic attack, and sudden cardiac death.
Men who had been prescribed testosterone treatment (given by injection, orally, or gel/cream) were found to have a 33% reduced incidence (hazard ratio 0.67) of cardiovascular end points during a follow-up period of up to 6.6 years, compared to men who had never been prescribed testosterone treatment.15 It was concluded that testosterone treatment is not associated with an increased risk of cardiovascular outcomes. In opposition to popular belief, during long-term follow-up the risk of cardiovascular events is lower in testosterone-treated men.15 These findings support both the safety and efficacy of testosterone therapy in testosterone deficient men.
Protective mechanisms of testosterone
The exact mechanisms by which therapeutic (normal) levels of testosterone might reduce risk of atrial fibrillation development remain to be established and are likely multifactorial. Data suggest that testosterone has anti-arrhythmogenic properties.8
Inflammation has been implicated in the pathogenesis of atrial fibrillation 16, 17, and inflammatory markers - including tumor necrosis factor α, interleukin 6, interleukin 2, and C-reactive protein – are elevated in patients with atrial fibrillation.18 Several studies have shown that endogenous testosterone levels are inversely associated with inflammatory markers, and that testosterone treatment decreases levels of tumor necrosis factor α, interleukin 6, C-reactive protein, and other proinflammatory cytokines.19-21 Thus, the anti-inflammatory and anti-arrhythmogenic effects of testosterone likely contribute to the observed reduced incidence of atrial fibrillation.
A report of two case studies suggested that testosterone could be used as an atrial fibrillation treatment in aging men 22, which is supported by the study presented here.