High Testosterone Levels Linked to Increased AFib Risk, Study Shows

High Testosterone Levels Linked to Increased AFib Risk, Study Shows


A new study has linked high testosterone levels in healthy older men with an increased risk of developing atrial fibrillation, which is a common cardiac condition that raises the chances of stroke.

The research builds off previous studies finding a relationship between testosterone levels and atrial fibrillation, commonly known as AFib. Most recently, a clinical trial called the Testosterone Replacement Therapy for Assessment of Long-term Vascular Events and Efficacy Response in Hypogonadal Men (TRAVERSE) study found that men with cardiovascular disease risk factors taking testosterone-replacement therapy, or TRT, may have a higher risk of AFib. 

But the new findings, published in the journal The Lancet, suggest that men with naturally higher levels of testosterone and no heart disease risk factors may also have an elevated Afib risk.

“Our results show that even in healthy men aged over 70 years with no prior history of cardiovascular disease—including AFib—the risk between higher testosterone concentrations and AFib is still present,” lead study author Cammie Tran, MPH, a researcher at Monash University in Australia, told Health.

Though the study doesn’t prove causation, Tran said it suggests AFib “may be an adverse consequence” of higher testosterone concentrations. “Clinicians should be aware of this risk when assessing testosterone concentrations in older men,” she said.

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AFib is the most common form of treated irregular heartbeat or arrhythmia. About 70% of people with AFib are between the ages of 65 and 85 years, with rates about equal for men and women. An estimated 12.1 million people will have AFib in the United States by 2030, according to the Centers for Disease Control and Prevention.

People with Afib have upper and lower chambers of the heart that don’t coordinate properly, causing the heart to beat abnormally—too slow, too fast, or irregularly. Some people have no symptoms, while others may feel fluttering in the chest, lightheadedness, shortness of breath, or chest pain.

The condition causes about one in seven strokes, which tend to be more severe when caused by Afib.

Tran’s team wanted to examine Afib risk among healthy older men not taking testosterone. 

To investigate this relationship, researchers gathered data on 4,570 men enrolled in the ASPREE clinical trial, a long-term examination of the effects of aspirin on health in older adults.

The participants, who were aged 70 or older, had no history of cardiovascular disease, prostate cancer, thyroid disease, dementia, or other life-threatening illnesses. 

The men provided blood and urine samples at the start of the study, and researchers followed up with them every six months for an average of three to five years. During that time, 286 men developed AFib.

Controlling for age, smoking status, and body mass index, the scientists found that men who developed AFib had higher initial average testosterone levels than those who didn’t—17 nanomoles per liter (nmol/L) vs. 15.7 nmol/L. Men with the highest testosterone levels had a greater risk of AFib compared to those with testosterone concentrations in the middle of the range.

“Our results show that the risk between testosterone and AFib is present in the highest 40% of testosterone concentrations,” Tran said. “So you can see that it is not uncommon to fall within this ‘at risk’ group.”

The relationship between testosterone and AFib risk was nonlinear, meaning that men whose testosterone levels fell below normal also had higher odds of developing AFib. 

“The non-linear relationship suggests that the risk of AFib could be lowered by keeping testosterone concentrations within the mid-range of the clinical normal range,” Tran said.

The findings reinforce the TRAVERSE study results, Steven Nissen, MD, a cardiologist at Cleveland Clinic who led that research, told Health. They “make the point that there appears to be this relationship between testosterone levels and atrial fibrillation.”

Megan Kamath, MD, a cardiologist at UCLA Health, told Health that the study shows that an “assessment of a patient’s total risk for atrial fibrillation given their age, comorbidities, and other medical considerations should be done when considering testosterone supplementation.” 

However, she added that more research is necessary to understand how testosterone levels affect Afib risk.

The study has several limitations. “Sample collection did not occur at a regular time of day,” Tran said, despite circadian rhythms being a known influencer of testosterone concentration.

Additionally, other sex hormones such as estradiol, free testosterone, dihydrotestosterone (DHT), and sex hormone binding globulin (SHGB) weren’t measured, per Tran, “restricting our ability to consider possible mechanisms” behind testosterone’s potential effect on Afib risk.

So far, research hasn’t uncovered exactly why testosterone might be related to heart health. But Tran suggested several possibilities.

Some evidence shows that people with higher testosterone have shorter telomeres, which research has associated with a higher risk of AFib.

“Other studies suggest that testosterone’s conversion to estradiol relates to expression of genes in fat at the surface of the heart, or that testosterone increases expression of receptors or excitability in heart tissues, predisposing to AF,” she added.

However, “these possibilities need to be examined further,” she said.

People with low testosterone levels might be interested in or prescribed testosterone replacement therapy to raise circulating levels of the hormone.

However, the study authors said that despite its limitations, the research reinforces the need for patients and medical providers to weigh both risks and benefits when a person is considering TRT. 

Sharing an accurate and complete medication list with doctors can help them make this calculation, Kamath emphasized.

If you opt for TRT, she said to pay attention to any new symptoms and share them with a medical professional. People with high testosterone levels may experience a number of symptoms, including: 

  • Acne
  • Excessive body hair
  • Aggressive or risk-taking behaviors
  • Headaches
  • High blood pressure
  • Increased appetite

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