Millions of Americans are at risk of a stroke from intense exercise

A recent study suggests that about 16.5 million Americans could be putting themselves at an increased risk of stroke due to intense physical exercise. The individuals at risk are those living with a condition known as carotid artery stenosis, which affects approximately five percent of the adult population in the United States.

Carotid artery stenosis is a disease characterized by the build-up of plaques within the carotid arteries, the crucial blood vessels running through the neck that are tasked with delivering oxygen and essential nutrients to the brain and parts of the face. The accumulation of plaque narrows these arteries, potentially compromising their function.

Alarmingly, regular physical activities such as brisk walking, swimming, or high-energy exercise could pose a significant threat to these individuals. According to the researchers, strenuous exercises can dislodge the plaque in the major arteries, which then travels to the brain and obstructs a blood vessel, leading to a stroke.

Five percent of Americans are at risk

The prevalence of carotid artery stenosis has seen a dramatic increase over the past two decades. Data from the early 2000s suggested that about two million Americans suffered from this condition. However, recent figures from the Cleveland Clinic indicate that the number has jumped to approximately 16.5 million, which accounts for about five percent of all adults in the country.

Risk factors for carotid artery stenosis include obesity, a sedentary lifestyle, diabetes, and smoking. Consequently, those affected may need to reconsider the intensity of their workout routines to mitigate the risk of suffering a stroke.

How the research was conducted 

The groundbreaking study, which was recently published in the journal Physics of Fluids, was conducted by building a computer simulation of a carotid artery. Three different carotid arteries were modeled, representing a healthy artery, one with a ‘mild’ 30 percent blockage, and one with a ‘severe’ 50 percent blockage.

Each model was then subjected to various heart rates corresponding to different levels of physical activity, including resting (67bpm), moderate exercise (100bpm), and strenuous exercise (140bpm). The latter heart rate can be achieved through brisk walking, cycling, or Zumba among other activities, especially in obese individuals.

What the researchers discovered 

The study revealed that exercise proved beneficial for the health of the carotid arteries that were either healthy or mildly blocked. However, for those with severe blockage, the results were characterized as “concerning.”

The simulation demonstrated increased stress on the severely blocked area, elevating the risk of rupture and subsequent dislodging of plaque into the bloodstream. This dislodged plaque could then travel to the brain, obstruct a blood vessel, and trigger a stroke.

“Intense exercise shows adverse effects on patients with moderate or higher stenosis levels,” explained Dr. Somnath Roy, a mechanical engineer at the Indian Institute of Technology Kharagpur and the study’s lead author. “It substantially increases the shear stress at the stenosis zone, which may cause the stenosis to rupture.”

This disrupted plaque, Dr. Roy added, could then potentially journey to the brain, interrupt its blood supply, and cause an ischemic stroke.

The researchers made clear that while intense exercise can improve the cardiac performance of healthy individuals, it could have severe consequences for patients with significant arterial blockages, particularly at elevated heart rates due to extensive physical activities.

Risk of stroke doubles post-exercise 

Further supporting this discovery, prior research, including an analysis of stroke patients from 2010 and a meta-analysis of 13,000 strokes in 2021 in Europe, indicates that the risk of stroke doubles post-exercise. These studies also linked acute anger, emotional upset, and heavy physical exertion to an elevated risk of stroke, primarily due to their impact on heart rate.

The findings demonstrate that various forms of stress, whether physical, such as intense exercise, or emotional, like acute anger or emotional upset, can result in a boosted heart rate. This increase can potentially dislodge plaque, subsequently leading to a stroke.

Dr. Andrew Smyth, an epidemiologist at the National University of Ireland, Galway, sheds light on the intricate connection between these trigger events and the risk of stroke. “We believe that these trigger events may increase the heart rate, increase blood pressure and lead to hormonal changes that alter blood flows in vascular beds such as the brain, which may increase the risk of stroke,” he told TODAY.

Nevertheless, Dr. Smyth was quick to reassure that not every stressful incident directly translates to a stroke. “That being said, not every episode of anger or emotional upset or heavy physical exertion leads to a stroke. Similarly, not every individual who has a high burden of cardiovascular risk factors will have a stroke.”

These revelations highlight the importance of understanding the individual and cumulative effects of various risk factors on the likelihood of a stroke, especially in populations already at risk due to conditions like carotid artery stenosis. The findings also underscore the need for personalized approaches to exercise, particularly for individuals with significant arterial blockages. 

The research adds another layer of complexity to the balance between the benefits of exercise and the potential risks for certain individuals, encouraging a nuanced conversation about the best ways to promote health and longevity.

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