A person’s resting heart rate is often seen as a simple sign of health. Many people believe that a lower resting heart rate always means the heart is healthier and stronger.
Athletes, for example, commonly have slower heartbeats because their hearts pump blood more efficiently.
But a major new study suggests that both very low and very high resting heart rates may actually be linked to a greater risk of stroke.
The findings were presented at the European Stroke Organization Conference 2026 and are based on one of the largest studies ever conducted on resting heart rate and stroke risk.
Researchers analyzed information from about 460,000 participants in the UK Biobank, a huge long-term health research project in the United Kingdom. Participants were followed for an average of 14 years, giving scientists a large amount of long-term health data to study.
During the study period, more than 12,000 participants experienced a stroke.
Researchers carefully adjusted the results to account for several major stroke risk factors, including age, sex, diabetes, high blood pressure, and atrial fibrillation. Atrial fibrillation is a condition that causes irregular heartbeats and is one of the strongest known risk factors for stroke.
After examining the data, researchers discovered a clear U-shaped pattern.
People whose resting heart rates were between 60 and 69 beats per minute had the lowest risk of stroke.
However, stroke risk increased at both extremes.
Participants with very low resting heart rates below 50 beats per minute had about a 25 percent higher risk of stroke. Meanwhile, people with high resting heart rates of 90 beats per minute or more had an even greater increase in risk, around 45 percent higher.
The researchers said this pattern remained even after accounting for many other health conditions. This suggests the relationship may represent a genuine biological effect rather than simply reflecting poor overall health.
One of the most interesting findings appeared when researchers separated participants based on whether they had atrial fibrillation.
The U-shaped pattern was mainly seen in people who did not have atrial fibrillation.
In people already living with atrial fibrillation, heart rate itself seemed much less important in predicting stroke risk.
Lead author Dr. Dexter Penn from Imperial College London explained that atrial fibrillation already increases stroke risk so strongly that it may hide the smaller effects linked to resting heart rate.
Doctors estimate that atrial fibrillation may increase stroke risk by roughly five times compared with people who do not have the condition.
Because of this, researchers believe resting heart rate may be especially useful as a warning sign in people without atrial fibrillation.
The study also explored why both slow and fast heart rates might increase stroke risk.
Very low heart rates were mainly linked to ischemic strokes. These strokes happen when blood flow to the brain becomes blocked.
Researchers think extremely slow heartbeats may reduce blood flow to the brain because the heart spends longer resting between beats. Over time, this reduced circulation could potentially contribute to stroke risk in some people.
High resting heart rates showed a different pattern. Faster heartbeats were linked to both ischemic strokes and hemorrhagic strokes, which occur when blood vessels in the brain rupture and bleed.
Scientists believe very fast heart rates may place extra stress on blood vessel walls and increase strain on the cardiovascular system over time.
The findings challenge the common belief that lower heart rates are always healthier.
However, experts strongly warn people not to panic if they naturally have a slow heart rate. Many healthy athletes and physically fit individuals normally have lower resting heart rates because their hearts work more efficiently.
Similarly, temporary increases in heart rate can happen for many reasons, including stress, anxiety, caffeine, lack of sleep, illness, dehydration, or exercise.
The researchers emphasized that heart rate should not be viewed alone. Instead, it should be considered alongside overall cardiovascular health.
Professor Alastair Webb, one of the study’s co-authors, said resting heart rate is an easy and widely available measurement that may deserve more attention in stroke prevention.
Because heart rate can be measured easily at home, researchers believe it could eventually become part of routine cardiovascular risk assessments.
At the same time, scientists caution that the study does not prove heart rate directly causes strokes. The research only shows a strong association between resting heart rate patterns and stroke risk.
Future studies will be needed to better understand whether heart rate itself contributes directly to stroke or whether it reflects other hidden health problems.
Researchers also want to investigate genetic factors and use long-term monitoring devices to better understand how heart rate changes over time.
The study further highlights how complicated cardiovascular health can be. Doctors already know that blood pressure, cholesterol, smoking, diabetes, obesity, sleep, and stress all influence stroke risk.
This research suggests resting heart rate may also provide valuable information, especially in people without atrial fibrillation.
If you care about stroke, please read studies about how to eat to prevent stroke, and diets high in flavonoids could help reduce stroke risk.
For more health information, please see recent studies about how Mediterranean diet could protect your brain health, and wild blueberries can benefit your heart and brain.
The findings were presented at the European Stroke Organization Conference 2026.
Source: Imperial College London.
