After examining data on more than 5m people from British GP practices, researchers from the University of Birmingham found that patients with a common heart problem have a greater chance of having a stroke or developing a form of dementia than previously thought.
While some people with atrial fibrillation (AF) – an irregular heartbeat – are considered at risk of having a stroke and given preventative medicine, others are not, reports The Independent.
Academics said the risk assessment tools used to decide who should be given these drugs only have “modest” capabilities, and do not factor in other blood clot-related illnesses like vascular dementia, caused by reduced blood flow to the brain.
To assess whether people with AF considered at low risk of strokes and other blood clots – who would not normally be prescribed blood thinners – might still suffer negative outcomes, they analysed the data of more than 5m patients.
They identified 36 340 AF patients with no history of stroke, a low perceived risk of stroke and no oral anticoagulant prescription, and tracked them for an average of five years to assess their risk of strokes, vascular dementia or death.
Their data were also compared with information held on 117 000 healthy people without AF.
Despite being in the low-risk group, some 3.8% of AF patients monitored had a stroke, compared with 1.5% of healthy people: 9% of people with AF died compared with 5% of healthy people.
People with the condition had 68% increased odds of developing vascular dementia, according to the study, published in the journal Nature Medicine.
Dipak Kotecha, professor of cardiology at the University of Birmingham and senior author of the study, said: “Atrial fibrillation is one of the most common heart conditions, with more than 60m cases expected worldwide by 2050. So it’s crucial we develop strategies to prevent not only stroke, but outcomes like dementia.”
Alastair Mobley, a PhD researcher at the University of Birmingham and first author of the paper, said: “This study demonstrates a clear correlation between AF and vascular dementia.
“This may have a similar mechanism to the association between AF and stroke. Ongoing clinical trials such as DaRe2THINK, currently being run by the University of Birmingham, are exploring whether blood thinners in lower-risk patients can provide a way to prevent these bad outcomes.”
Atrial fibrillation causes an irregular and often abnormally fast heart rate: some people with the condition have a heart rate of more than 100 beats a minute.
It is the most common heart rhythm disturbance, affecting around 1.4m people in the UK.
The condition has been linked to developing blood clots and there are “numerous” tools to estimate stroke risk among people with AF but researchers said “these have only a modest predictive capacity” and do not consider other outcomes such as vascular dementia.
The authors highlight how guidelines from the National Institute for Health and Care Excellence and others recommend anticoagulant use only in patients with an elevated stroke risk score.
They said that more trials are needed to asses whether patients with AF could benefit from earlier use of blood thinners to prevent these bad outcomes.
Study details
Thromboembolic events and vascular dementia in patients with atrial fibrillation and low apparent stroke risk
Alastair Mobley, Anuradhaa Subramanian, Dipak Kotecha et al.
Published in Nature Medicine on 5 June 2024
Abstract
The prevention of thromboembolism in atrial fibrillation (AF) is typically restricted to patients with specific risk factors and ignores outcomes such as vascular dementia. This population-based cohort study used electronic healthcare records from 5 199 994 primary care patients (UK; 2005–2020). A total of 290 525 (5.6%) had a diagnosis of AF and were aged 40–75 years, of which 36 340 had no history of stroke, a low perceived risk of stroke based on clinical risk factors and no oral anticoagulant prescription. Matching was performed for age, sex and region to 117,298 controls without AF. During five years’ median follow-up (831 005 person-years), incident stroke occurred in 3.8% with AF versus 1.5% control (adjusted hazard ratio (HR) 2.06, 95% confidence interval (CI) 1.91–2.21; P < 0.001), arterial thromboembolism 0.3% versus 0.1% (HR 2.39, 95% CI 1.83–3.11; P < 0.001), and all-cause mortality 8.9% versus 5.0% (HR 1.44, 95% CI 1.38–1.50; P < 0.001). AF was associated with all-cause dementia (HR 1.17, 95% CI 1.04–1.32; P = 0.010), driven by vascular dementia (HR 1.68, 95% CI 1.33–2.12; P < 0.001) rather than Alzheimer’s disease (HR 0.85, 95% CI 0.70–1.03; P = 0.09). Death and thromboembolic outcomes, including vascular dementia, are substantially increased in patients with AF despite a lack of conventional stroke risk factors.
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