A long‑held belief in cardiovascular medicine is quietly being challenged. For decades, a low resting heart rate has been viewed as a sign of physical fitness and efficient heart function, while a high resting heart rate has been seen as a warning flag.
Now new research presented at the European Stroke Organisation Conference in 2026 suggests the reality is more complex, and potentially more concerning.
In the largest population‑level study to examine resting heart rate and stroke risk, researchers report that both unusually low and unusually high heart rates are linked to a higher chance of stroke.
The findings point to a clear U‑shaped relationship. In other words, extremes at either end of the heart rate spectrum appear to carry added risk, while the lowest risk sits squarely in the middle.
In Malaysia, stroke is the third leading cause of death in Malaysia, with an estimated prevalence of over 440,000 cases and roughly 48,000 new incidents yearly. Alarmingly, cases among younger adults are rising.
The research draws on data from the UK Biobank, one of the world’s most extensive health research resources. Scientists analysed health records from more than 460,000 adults and followed them for an average of 14 years. Over that time, more than 12,000 participants experienced a stroke, offering a powerful dataset to explore subtle risk patterns that smaller studies often miss.
After accounting for age, sex and a wide range of cardiovascular risk factors, including high blood pressure, diabetes and atrial fibrillation, the pattern remained strikingly consistent. Stroke risk was lowest among individuals whose resting heart rate fell between 60 and 69 beats per minute. Below 50 beats per minute, the risk rose by around 25%. At 90 beats per minute or higher, the increase was even more pronounced, reaching approximately 45%.
Such findings complicate the popular narrative that a lower heart rate is always better. While elite athletes often have resting heart rates well below 60 beats per minute without apparent harm, this study suggests that, at a population level, very low rates may not be universally benign. It raises important questions about how resting heart rate should be interpreted in routine clinical practice.
“Stroke risk was lowest among individuals whose resting heart rate fell between 60 and 69 beats per minute”
The study also explored whether this relationship held true across different groups. When participants were divided according to whether they had atrial fibrillation, an irregular heart rhythm and a major cause of stroke, a crucial distinction emerged. The U‑shaped pattern was present only in people without atrial fibrillation. In those with the condition, heart rate did not appear to meaningfully alter stroke risk.
Researchers believe this is because atrial fibrillation itself is such a dominant risk factor. It increases the likelihood of stroke by around five times, potentially overshadowing any additional influence of resting heart rate. In practical terms, this means heart rate may be a more useful signal in people who do not already have this well‑recognised condition.
From a clinical perspective, this nuance matters. Atrial fibrillation is often actively monitored and treated, with anticoagulant medications prescribed to reduce stroke risk. For the much larger group of people without the condition, risk assessment relies more heavily on traditional markers such as blood pressure, cholesterol and smoking status. Resting heart rate, a simple measurement taken in seconds, could offer an additional layer of insight.
“Below 50 beats per minute, the risk rose by around 25%. At 90 beats per minute or higher, the increase was even more pronounced, reaching approximately 45%”
The researchers also examined the types of stroke associated with heart rate extremes. Very low resting heart rates were mainly linked to ischaemic stroke, the most common form, caused by a blockage in a blood vessel supplying the brain. One possible explanation lies in blood flow dynamics. A slower heart rate means longer pauses between beats. In some individuals, this could reduce cerebral blood flow enough to increase vulnerability to clot formation.
High resting heart rates told a different story. They were associated with both ischaemic and haemorrhagic stroke, the latter involving bleeding within the brain. This dual association suggests a broader impact on the vascular system. A persistently elevated heart rate may reflect heightened stress on blood vessel walls, inflammation or autonomic nervous system imbalance, all of which can damage blood vessels over time.
These biological mechanisms remain hypotheses rather than proven pathways. However, they fit with existing knowledge about how the cardiovascular system responds to chronic stress and strain. A fast‑beating heart works harder, consumes more oxygen and may accelerate wear on the arteries. At the other extreme, a heart that beats too slowly may not deliver blood efficiently under certain conditions.
Importantly, the researchers stress that the study does not prove causation. A resting heart rate could be a marker rather than a direct cause of stroke risk. It may reflect underlying health issues that themselves increase risk, such as poor autonomic regulation, undiagnosed heart disease or the effects of certain medications. Untangling cause and effect will require further investigation.
Even so, the size and duration of the study lend weight to its conclusions. Few previous studies have been large enough, or followed participants for long enough, to detect this kind of U‑shaped pattern with confidence. Many earlier investigations focused on high heart rate alone, reinforcing the idea that slower is always safer.
The findings also highlight the value of large‑scale biobank data in uncovering unexpected health relationships. By combining detailed baseline measurements with long‑term follow‑up, researchers can move beyond simple yes‑or‑no risk factors and explore more nuanced patterns across the population.
From a public health standpoint, the implications are intriguing. Resting heart rate is easy to measure, non‑invasive and inexpensive. It can be recorded in a clinic, at home, or even through wearable devices. If future studies support these findings, heart rate could become a more prominent feature of cardiovascular risk assessments, particularly for people who do not have atrial fibrillation.
That does not mean individuals with low or high heart rates should panic. Stroke risk is influenced by many factors, and heart rate is only one piece of a complex puzzle. Lifestyle choices such as regular physical activity, a balanced diet, not smoking and managing blood pressure remain the cornerstones of prevention.
However, the study suggests that extremes in resting heart rate should prompt closer attention. A very low heart rate in a non‑athlete, or a persistently high rate at rest, may warrant a more thorough cardiovascular evaluation. It may also encourage clinicians to reinforce existing prevention strategies rather than assume all is well.
The researchers are clear that more work lies ahead. Future studies will explore whether genetic factors linked to heart rate also influence stroke risk. Others will use repeated measurements or continuous monitoring to capture how heart rate changes over time, rather than relying on a single reading. This is particularly relevant in an era of smartwatches and fitness trackers, which generate vast amounts of heart rate data.
Another important step will be to confirm these findings in more diverse populations. The UK Biobank largely reflects a specific demographic profile, and stroke risk factors can vary across ethnic, cultural and socioeconomic groups. Broader studies will help determine how widely these results apply.
For now, the message is one of cautious recalibration rather than alarm. The heart’s rhythm, it seems, carries information beyond what was previously appreciated. Neither too slow nor too fast appears ideal when it comes to long‑term brain health.
In a field where simple metrics are often overshadowed by complex imaging and laboratory tests, this research brings attention back to a basic physiological measure. Resting heart rate, long taken for granted, may deserve a second look.
As evidence grows, it could become a quiet but valuable signal in the ongoing effort to prevent stroke, one of the leading causes of death and disability worldwide.
By challenging assumptions and opening new avenues of inquiry, this study underscores an enduring truth of medical science. Even the most familiar measurements can hold surprises, especially when examined at scale and over time.
For clinicians, researchers and the public alike, it is a reminder that cardiovascular health rarely conforms to simple rules and it deserves way more attention.
The post These Numbers of Heart Rates Significantly Associated with Stroke Risk, New Research Finds first appeared on PP Health Malaysia.
