ACST-1 Long Term Follow-up


ACST-1 (ISRCTN26156392) was an international randomised trial, which recruited 3120 patients between 1993-2003. The original aim was to find out whether carotid surgery (endarterectomy) plus medical treatment prevented more strokes compared with medical treatment alone in patients with carotid stenosis, a condition where one or both carotid arteries (the main blood vessels that supply the front of the brain) 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 ACST-1 long-term follow-up study 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, which may have been substantially underestimated in the relatively brief 5 and 10-year previously published results of ACST-1.

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 (necessary since dementia is an insidious condition taking many years to develop) represents a unique opportunity to directly assess the effect of surgery on dementia risk. If we demonstrate that carotid surgery not only lowers the risk of stroke but also prevents dementia, many more patients may be considered for carotid surgery thereby reducing the health burden 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. NHS Digital will provide us with information contained only in hospital NHS electronic health records (hospital admissions, hospital outpatient, A&E attendances and mental health). We will obtain mortality data (date and cause of death) from the Personal Demographics Service dataset held by NHS Digital. The ONS mortality data are provided by NHS Digital on behalf of ONS and is sourced from Civil Registration Data. We will also obtain data from the National Dementia & Antipsychotic Prescribing Audit 2006-2011 (DAP) that provides ‘dementia-specific’ medication prescribed by GPs.

Collectively, these data 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 will be used solely for academic research purposes by the study team in Oxford.

We also plan to follow-up the ACST-1 UK participants with a questionnaire on memory and thinking (cognition) called the ‘ Informant Questionnaire on Cognitive Decline in the Elderly’ (IQCODE). This will be completed, over the telephone by a close relative or friend (the informant) of the ACST-1 participant, with the study nurse. This part of the study called ACST-1 follow-up study of memory and thinking function will measure any changes in memory or thinking in the ACST-1 participant over the last 10 years. The results from the IQCODE assessment will complement the data linkage data as described above.

The personal data will be kept for 15 years from 23rd February 2018 until 28th February 2033.

Data protection regulation provides control over the use of personal data although some of those rights may be limited in order for the research to be reliable and accurate. Further information including the right to object with a supervisory authority (Information Commissioner’s Office) can be found here

To make a complaint regarding data privacy please contact the University of Oxford, Data Protection Officer at:


By post: University Offices, University of Oxford, Wellington Square, Oxford, OX1 2JD

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 Department of Population Health (NDPH), University of Oxford data sharing policy:

To find out more about this long term follow up please see:

ACST-1 Long-term follow-up protocol

ACST-1 Long-term follow-up overview and contact details

ACST-1 follow-up study of memory and thinking function

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 this way 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: +44 (0)1865 61 79 79 between 9am-4pm on weekdays

This ACST-1 long-term follow-up study is funded by an Alzheimer’s Society

project grant.