Long-term follow-up of Asymptomatic Carotid Surgery Trial (ACST-1)
Research type
Research Study
Full title
Does surgery for asymptomatic carotid stenosis reduce the long term risk of dementia, stroke, death and other important health outcomes? Extended post-trial follow-up of the Asymptomatic Carotid Surgery Trial (ACST-1).
IRAS ID
194088
Contact name
Alison Halliday
Contact email
Sponsor organisation
Clinical Trials Research Governance, University of Oxford
ISRCTN Number
ISRCTN26156392
Duration of Study in the UK
1 years, 9 months, 1 days
Research summary
Summary of Research
People with narrowing of their carotid artery (a large blood vessel in the neck) are at a higher risk of ischaemic stroke in the long-term, and there is a suggestion that they are also at a higher risk of dementia. We know that an operation to remove narrowing of the carotid artery (‘carotid endarterectomy’) reduces the risk of stroke, but we do not know whether it reduces the risk of dementia.
ACST-1 was a large, publicly-funded, international, randomised trial that randomly allocated participants with narrowing of the carotid artery to carotid endarterectomy or no endarterectomy. The trial showed endarterectomy reduced the risk of stroke at 5 and 10 years after the operation by a small amount.
Small reductions in the risk of stroke might lead to larger reductions in the risk of dementia in the long term. We plan to investigate this question by analysing long-term data of approximately 22 years duration from UK and Swedish electronic health records on the participants for dementia, stroke and death.If we showed that endarterectomy for carotid stenosis without symptoms reduced the risk of dementia, this would be influential, because this treatment is not widely used in the NHS as surgery reduces the risk of stroke by only a small amount. A reduction in the risk of dementia would alter the risks and benefits of surgery, and provide better information to patients and clinicians.
Summary of Results
The research question whether carotid endarterectomy (CEA- carotid artery surgery) might protect against dementia by reducing future stroke risk and improving cerebral blood flow has been answered. The study also showed that it is possible to use electronic health records to follow participants over a long period of time.
In this study to determine stroke and dementia diagnosis, we linked 1601 UK and Swedish participants to national electronic health records and registries for hospital episodes, mental health and medication datasets and all-cause of death. It was found that allocation in the study to immediate or later CEA did not appear to reduce dementia risk despite a reduction of stroke risk at five and ten years. The frequency of dementia in the participants over 75 years of age, with a blockage in the carotid artery in the neck (with no symptoms), is high. Participants with prior diabetes or a brain infarct (loss of blood to an area of the brain) is also closely associated with dementia risk. Because stroke is closely associated with dementia risk it remains possible that the prevention of stroke in specific high risk populations may be beneficial in preventing dementia. European guidelines will continue to consider whether particular groups of asymptomatic participants might benefit from carotid artery surgery but a large, long-term randomised study will be necessary to determine this.REC name
South Central - Oxford C Research Ethics Committee
REC reference
16/SC/0406
Date of REC Opinion
6 Sep 2016
REC opinion
Favourable Opinion