For years, many people have believed that having a low resting heart rate is always a sign of excellent health. Fitness trackers, smart watches, and health apps often encourage people to lower their resting heart rates as much as possible.
But a large new study suggests the relationship between heart rate and health may be more complicated.
Researchers presenting their findings at the European Stroke Organization Conference 2026 found that both very low and very high resting heart rates were linked to a greater risk of stroke.
The study is considered the largest population-level analysis ever conducted on this topic.
Scientists used data from the UK Biobank, a huge long-term health database that tracks the medical information of hundreds of thousands of people in the United Kingdom.
The study included about 460,000 participants who were followed for an average of 14 years. During that time, more than 12,000 strokes occurred.
Researchers adjusted the results for major stroke risk factors including age, sex, diabetes, hypertension, and atrial fibrillation.
Atrial fibrillation is an irregular heartbeat disorder that greatly increases the risk of stroke because it can cause blood clots to form inside the heart and travel to the brain.
After analyzing the data, researchers discovered that the safest resting heart rate range appeared to be between 60 and 69 beats per minute.
People whose resting heart rates fell within this range had the lowest stroke risk.
However, stroke risk increased at both lower and higher heart rates.
Participants with resting heart rates below 50 beats per minute had a 25 percent higher risk of stroke compared with the middle group.
Meanwhile, people with resting heart rates of 90 beats per minute or higher had an even greater increase in stroke risk, about 45 percent higher.
Researchers described the findings as forming a “U-shaped” relationship, meaning the lowest risk was in the middle range while risk rose at both extremes.
Importantly, the pattern remained even after researchers adjusted for many other cardiovascular risk factors. This suggests resting heart rate itself may contain useful information about stroke risk.
The researchers then looked separately at people with and without atrial fibrillation.
Interestingly, the U-shaped relationship was mainly visible in people without atrial fibrillation.
Lead researcher Dr. Dexter Penn explained that atrial fibrillation is such a powerful stroke risk factor that it may overshadow smaller effects linked to heart rate.
This means resting heart rate may be most useful for identifying risk in people who do not already have atrial fibrillation.
Researchers also investigated why both low and high heart rates might be associated with stroke.
Very low heart rates were mainly linked to ischemic strokes, which happen when blood supply to the brain becomes blocked.
Scientists suspect extremely slow heart rates could reduce blood flow to the brain because the heart pauses longer between beats.
In contrast, very fast heart rates were associated with both ischemic strokes and hemorrhagic strokes, which occur when blood vessels burst and bleed into the brain.
Researchers believe elevated heart rates may place greater stress on blood vessels over time, increasing the chance of damage.
The study highlights how the body’s systems are carefully balanced. While extremely high heart rates can signal stress on the cardiovascular system, extremely low heart rates may also sometimes reflect hidden problems.
Still, experts stress that heart rate should always be interpreted carefully.
Many healthy athletes naturally have low resting heart rates because their cardiovascular systems are highly efficient.
Similarly, heart rate can change from day to day depending on stress, exercise, sleep quality, illness, medications, caffeine, hydration, and emotional state.
Professor Alastair Webb from Imperial College London said resting heart rate is an inexpensive and easily available measurement that may deserve greater attention during routine cardiovascular assessments.
Because it can be measured easily at home or during doctor visits, heart rate may eventually become an additional tool for identifying people who need closer cardiovascular evaluation.
However, researchers caution that the study does not prove heart rate directly causes stroke.
Instead, heart rate may simply act as a signal that reflects other biological processes or hidden health conditions affecting the cardiovascular system.
The researchers say more studies are now needed to understand whether changing resting heart rate can actually reduce stroke risk.
Future research will also examine genetic influences and use continuous heart monitoring devices to better understand how long-term heart rate patterns affect health.
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The findings were presented at the European Stroke Organization Conference 2026.
Source: Imperial College London.
