A new study presented earlier today at the 2026 European Stroke Organisation Conference (ESOC; 6–8 May, Maastricht, Netherlands) suggests that both very low and very high resting heart rates are linked with an increased risk of stroke. These findings from the largest population-level study to examine this relationship can be seen to challenge prior assumptions that lower heart rates carry no risk and are always a sign of good cardiovascular fitness.
In an analysis of the UK Biobank, researchers followed 460,000 participants for an average of 14 years, during which 12,290 strokes occurred. Analyses were adjusted for age, sex and cardiovascular risk factors, including atrial fibrillation (AF).
Stroke risk was lowest at resting heart rates of 60–69bpm but increased at both extremes—below 50bpm, and at or above 90bpm—forming a clear ‘U-shaped pattern’. At these extremes, stroke risk was 25% higher in those with very low heart rates and 45% higher in those with very high heart rates. Additionally, in the overall study population, this relationship remained after adjustment for established stroke risk factors including hypertension, diabetes and AF, suggesting it reflects a genuine biological signal.
However, when participants were analysed separately, this pattern was only seen in people without AF, while the relationship was not apparent in those with the condition.
“This is likely because AF is such a strong risk factor for stroke—increasing risk by around fivefold—that it outweighs the contribution of heart rate and limits our ability to detect its effect,” explained lead study author Dexter Penn (Imperial College London, London, UK). “Heart rate was therefore most informative in people without AF, where it may provide a valuable additional tool for identifying and stratifying stroke risk.”
The researchers also explored the potential mechanisms underlying the relationship between heart rate and stroke. Very low heart rates were primarily associated with ischaemic stroke, which the researchers note would be consistent with the hypothesis that very low heart rates could be associated with reduced blood flow to the brain by prolonging the relaxation phase between heartbeats.
In contrast, elevated heart rates were associated with both ischaemic and haemorrhagic stroke—potentially suggesting increased stress on blood vessel walls that could contribute to both ischaemic injury and a greater predisposition to bleeding.
Commenting on the clinical implications of these findings, co-author Alastair Webb (Imperial College London, London, UK) said: “Resting heart rate is a simple, widely available measure that deserves greater attention in cardiovascular risk assessment, particularly in people without AF.
“More research is required to understand why both low and high heart rates may be associated with an increased stroke risk, and what implications this may have for treatment, but very low or very high heart rates should act as a signal for clinicians to look more closely at an individual’s overall cardiovascular risk, and take action to reinforce lifestyle changes and standard prevention strategies.”
The authors emphasise that further research is needed to better understand whether resting heart rate plays a causal role in stroke or reflects underlying health. This will include studies exploring genetic factors linked to heart rate, as well as research using repeated or continuous monitoring to better capture how heart rates change over time. It will also be important to confirm these findings in more diverse populations, the authors add.
