Flu And Stroke: Is There A Link?

The flu has been linked to an increased risk of stroke and ruptured arteries. Two studies have found that flu-like symptoms increase the likelihood of a stroke by about 40% over the following 15 days. The risk of stroke is greatest within a month of a flu-like illness. While the reason for the link between the flu and stroke is not known, researchers suspect it could be due to inflammation caused by the infection. Viral infections, such as the flu, can cause inflammation and dilation of the heart, leading to the development of clots that can cause a stroke.

Flu-like illnesses increase the risk of stroke by 40%

The study found that people had a 40% higher chance of having a stroke if they had been admitted to hospital with flu-like symptoms within the past 15 days. The risk was highest in the 15 days following the onset of flu-like symptoms and decreased over time.

While the exact reason for the link between flu-like illnesses and stroke is unknown, researchers suspect it could be due to inflammation caused by the infection. Inflammation is an increasingly recognised risk factor for stroke, and flu can cause internal swelling that leaves the body vulnerable to strokes and heart attacks.

The findings of the study highlight the importance of getting vaccinated against the flu, as it can not only protect against the infection but also reduce the risk of serious complications such as stroke.

Flu-like symptoms are linked to ruptured neck arteries

Flu-like symptoms have been linked to ruptured neck arteries, which can lead to a stroke. This is known as cervical artery dissection (CAD), and it occurs when there is a tear in one of the arteries of the neck, allowing blood to leak into the layers of the artery wall and causing a blockage in blood flow to the brain.

Two studies have found a link between flu-like symptoms and an increased risk of CAD. The first study, conducted by researchers from Columbia University's Vagelos College of Physicians and Surgeons, analysed data from nearly 31,000 people who were hospitalized with an ischemic stroke in 2014. The study found that having flu-like symptoms increased the likelihood of having a stroke by about 40% over the next 15 days, and the overall risk of experiencing a stroke was increased for up to a year.

The second study, conducted by researchers from the same institution, looked at data from about 3,800 people who had CAD between 2006 and 2014. The researchers found that these patients were about 50 to 60% more likely to have had a flu-like illness in the month before their CAD diagnosis, compared to the same time period in previous years.

The exact reason for the link between flu-like illness and CAD is not yet known, but researchers suspect it could be related to inflammation caused by the infection. While the studies only found an association between flu-like symptoms and CAD, the findings highlight the importance of taking precautions against the flu, such as getting a flu shot and practising good hygiene.

It is worth noting that while the link between flu-like symptoms and ruptured neck arteries is concerning, the overall risk of experiencing a stroke is relatively low. Additionally, cervical artery dissections are rare, occurring in only about two in 100,000 people per year. However, they are one of the most common causes of stroke in people under the age of 50.

Flu-related inflammation can cause clots and blockages

The flu has been linked to an increased risk of stroke and ruptured arteries, particularly in the neck. Research has found that flu-like symptoms increase the likelihood of having a stroke by about 40% over the following 15 days. The risk of stroke is greatest within a month of a flu-like illness.

The flu can cause inflammation and dilation of the heart, which can lead to a weakening of the heart muscle. This, in turn, can cause an abnormal heart rhythm or low output from the heart, resulting in the development of a clot. These clots can travel through the bloodstream and block the flow of blood to the brain, causing a cardioembolic stroke.

Cardioembolic strokes are a common type of stroke, accounting for approximately 20% of ischemic strokes. They occur when there is a blockage of a brain blood vessel. Patients with certain cardiac abnormalities or vascular risk factors are at higher risk for clot-related strokes. These risk factors include hypertension, high cholesterol, decreased physical activity, and heavy alcohol consumption.

The link between flu and stroke is not fully understood, but researchers suspect that inflammation caused by the infection may play a role. The flu can cause acute and severe inflammation, which can destabilize plaques in the coronary arteries. This can lead to the rupture of these plaques and the formation of clots, resulting in heart attacks and strokes.

While the flu can increase the risk of stroke, it is important to note that it does not directly cause strokes. However, the findings highlight the importance of getting a flu shot, especially for those with cardiac risk factors.

Flu can cause heart problems, triggering strokes

The flu can cause heart problems, which in turn can trigger strokes. In 2018, actor Harry Anderson died from a cardioembolic stroke, a common type of stroke involving the blockage of a brain blood vessel. The contributing factor in Anderson's case was influenza, which caused inflammation and dilation of his heart. Anderson developed cardiomyopathy, or weakness of the heart muscle, which either caused an abnormal heart rhythm or low output from his heart, leading to the development of a clot that travelled to his brain.

Cardioembolic strokes account for approximately 20% of ischemic strokes, but that number could be as high as 30% if a clot develops due to another heart problem. Patients with certain cardiac abnormalities or significant vascular risk factors are at increased risk for clot-related strokes. These cardiac abnormalities include:

• Atrial fibrillation (AFib), a type of abnormal heart rhythm
• Heart failure, or low ejection fraction
• Patent foramen ovale (PFO), a hole in the heart that should have closed after birth
• Hypercoagulable state, or excessive clotting

Viral infections, such as the flu, can cause inflammation and dilation of the heart, which can lead to the development of clots. These clots can travel through the bloodstream and block blood flow to the brain, resulting in a cardioembolic stroke. While Anderson's situation is considered rare, it can happen to people of any age, particularly those with risk factors that predispose them to clot-related strokes.

Research has also found a link between the flu and an increased risk of heart problems, including heart attacks. Influenza outbreaks are associated with a rise in deaths from heart disease, and the flu can trigger heart attacks and strokes. The flu causes acute and severe inflammation in the body, which can destabilize atherosclerotic plaques in coronary arteries, leading to the rupture of these plaques and the formation of clots. Additionally, the flu can cause bacterial pneumonia, which puts a strain on the heart as it has to work harder to pump blood through the lungs.

It is important to note that while the flu can increase the risk of heart problems and strokes, it is not the sole cause. Other risk factors include weight, smoking status, age, and family history. However, taking precautions such as getting a flu shot, frequent handwashing, and limiting public outings during flu outbreaks can help reduce the risk of viral infections and their potential complications.

Flu vaccinations may reduce the risk of stroke

It is well-known that respiratory infections can increase the risk of stroke in the days following infection. Flu symptoms can come on suddenly, including a cough, sore throat, fatigue, and sometimes a fever. Dr Gyanendra Kumar, a Mayo Clinic neurologist, explains that "some of these are increased hypercoagulable state, a transient period where you have a greater predisposition to form clots". When clots form, they can block blood flow to the brain, resulting in a cardioembolic stroke.

A recent study published in Stroke, an American Heart Association journal, found that flu vaccinations might lower the chances of stroke among adults, especially those under 45. This is supported by a 2018 study that found the risk of a heart attack was six times higher within a week of a confirmed flu infection. The findings were most pronounced for older adults and those experiencing their first heart attack.

In addition, a 2020 study that looked at more than 80,000 US adults hospitalized with the flu over eight flu seasons found that sudden, serious heart complications occurred in one out of every eight patients (approximately 12% of patients). Overall, flu vaccination has been associated with lower rates of some cardiac events, especially among those with heart disease who have had a cardiac event in the past year.

Therefore, it is recommended that people with heart disease or a history of stroke get a flu vaccine every flu season to protect against flu and its potentially serious complications.

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