ACST-1 (ISRCTN26156392) is an international randomised trial which recruited over 3000 patients between 1993-2003. The original aim of this trial was to find out whether carotid surgery (endarterectomy) and best medical treatment prevented more strokes compared with best medical treatment alone in patients with carotid stenosis. Carotid stenosis is a condition where one or both of the carotid arteries (the main blood vessels that supply the head and neck) become narrowed due to a build-up of fatty deposits (plaque). This increases the risk of having a stroke, when the blood supply to part of the brain is cut off.
The long-term follow-up of ACST-1 has two main aims: 1) To assess the effect of carotid surgery on long-term dementia risk; and 2) To assess the long-term effect of carotid surgery on stroke, since it is probable that the beneficial effects on stroke seen in ACST-1 at 5 and 10 years substantially underestimate the true ‘lifetime’ effect of successful intervention.
Patients with carotid stenosis are at increased risk of developing dementia, but there is no evidence that carotid endarterectomy reduces the risk of developing this debilitating condition. A randomised trial like ACST-1 with very long follow-up (which is necessary since dementia is an insidious condition which takes many years to develop) represents a unique opportunity to directly assess the effect of surgery on dementia risk. This question is highly relevant. If we demonstrate that carotid surgery not only lowers the risk of stroke but also prevents dementia, many more patients will be considered for carotid surgery thereby reducing the burden of disease posed by dementia.
For this follow-up study we will provide NHS Digital with first and last name, Date of Birth and NHS number of UK ACST-1 study participants thereby allowing them to provide us with information contained only in hospital NHS electronic health records (hospital admissions, hospital out-patient and A&E attendances and mental health). We will also obtain mortality data (date of death) from the Personal Demographics Service dataset held by NHS Digital. The ONS Mortality is provided by NHS digital on behalf of ONS and is sourced from Civil Registration Data. This will allow us to compare rates of stroke and dementia in one group of patients who were originally allocated carotid endarterectomy versus another group who did not have immediate surgery and received medicine alone. This information received from NHS Digital (which is patient identifiable data) will be imported into an existing, empty ACST-1 database held securely by The University of Oxford (Data Controller), and used solely for academic research purposes by the study team in Oxford. Before analysing this complete dataset (including information already provided by trial participants up to 2008 with information from NHS Digital) patient identifiers will be removed. Importantly, whilst the information received is specific to each trial participant, no individual person will be identifiable in any publication arising from this work. Furthermore, the ACST-1 database will not be shared with organisations outside of the University of Oxford and only accredited researchers in ACST-1 group, CTSU, University of Oxford will have access to the data. Anonymous results of the study may be made available to ACST collaborators and relevant bone fide researchers according to the Nuffield Depart of Population Health (NDPH), University of Oxford data sharing policy: https://www.ndph.ox.ac.uk/about/data-access-policy
To find out more about this long term follow up please see:
What to do next?
ACST-1 participants originally consented to their medical records being accessed
and do not need to take any further action if they agree to the data linkage proposed.
However, if participants decide they do not want their study data to be linked in thisway they can withdraw from this follow-up, without affecting their current medical care, by contacting the Study Coordinator, Mary Sneade at the ACST trials office:
or Tel: 01865 617978 between 9am-4pm on weekdays
This ACST-1 long-term follow-up study is funded by an Alzheimer’s Society