Plain English Summary
Background and study aims
As we get older our brains also begin to age, resulting in a 'slowing down' of abilities such as memory or reasoning. These mental processes are collectively known as ‘cognition’. In some people, cognition declines further, leading to cognitive impairment or dementia, which affects 800,000 people in the UK. Therefore, dementia and cognitive decline are a major public health issue, and there is increasingly a need to identify means of preventing or reducing the risk of dementia in order to improve the health of ageing populations worldwide. There is a growing body of evidence that indicates that people may be able to reduce their risk of dementia through certain lifestyle habits or activities. This is particularly true for people who are at higher risk due to their current cognitive abilities, lifestyle or overall health.
One promising avenue for reducing risk of dementia is through dietary supplementation of Vitamin D. Vitamin D is produced by the body when exposed to sunlight during summer months and is available in some foods such as fish and eggs. However, a large proportion of older adults do not receive enough Vitamin D and few people take regular dietary supplements. Vitamin D is known to play an important role in brain health and cognition, and may improve cognition and reduce the risk of dementia.
This study will provide vitamin D supplementation to people at risk of dementia, with the aim of determining whether this can reduce the risk of cognitive decline and dementia in older adults.
Who can participate?
People aged over 50 who have early changes in brain function (Age-Associated Cognitive Decline) and are at risk of vitamin D deficiency in their diet
What does the study involve?
Participants will be randomly allocated to receive either daily vitamin D supplements or a placebo (dummy pill). Pills will be taken daily for three years. Assessments will be completed at the beginning of the trial, after six months, one, two and three years. The trial is being run using an online platform, meaning that registration, consent and all assessments will be completed online. Participants will log into a study portal, called the PROTECT study, and complete all study tasks through their computer
What are the possible benefits and risks of participating?
Participants in the treatment group may benefit from the dietary supplement through improvements to cognition if the trial is successful. All participants will be able to register on the national PROTECT cohort study as part of their involvement, which includes annual cognitive assessments and access to brain training games. There are no known risks to participants taking part in this study.
Where is the study run from?
University of Exeter (UK)
When is the study starting and how long is it expected to run for?
June 2018 to October 2022
Who is funding the study?
JP Moulton Foundation (UK)
Who is the main contact?
Dr Anne Corbett
Dr Anne Corbett
St Luke's Campus
University of Exeter Medical School
A randomised clinical trial of vitamin D to improve cognition in people at risk of dementia
Vitamin D supplementation will confer benefit to cognition in adults with AACD compared to placebo
Approved 05/03/2019, Ethics Board: Wales REC 3 (Health and Care Research support Centre, Castlebridge 4, 15-19 Cowbridge Road East, Cardiff, CF11 9AB, UK; Email: Wales.REC3@wales.nhs.uk), REC ref: 19/WA/0007, IRAS number: 247136
Interventional double-blind placebo-controlled two-arm single-centre randomised controlled trial
Primary study design
Secondary study design
Randomised controlled trial
Patient information sheet
Age-associated cognitive decline
Current interventions as of 23/07/2019:
Participants will be randomised into either the treatment or control arm of the study. Randomisation is achieved through simple randomisation delivered through REDCap Cloud following stratification for age, gender, cognitive status and level of estimated vitamin D deficiency.
The active treatment arm will receive two-piece HPMC capsules containing Vitamin D3 (4000IU) produced by Healthspan as their product ‘Elite Vitamin D3’. Participants will receive one capsule daily, by oral administration, over three years. The control group will receive an identical placebo capsule with the same treatment regimen. Follow-up is conducted online through computerised assessment at baseline, 26, 52, 104 and 156 weeks. Participants receive automated reminders to log into their study portal and complete all assessments.
Participants will be randomised into either the treatment or control arm of the study. Randomisation is achieved through simple randomisation delivered through the online study portal (PROTECT), following stratification for age, gender and cognitive status.
The active treatment arm will receive two-piece HPMC capsules containing Vitamin D3 (4000IU) produced by Healthspan as their product ‘Elite Vitamin D3’. Participants will receive one capsule daily, by oral administration, over three years. The control group will receive an identical placebo capsule with the same treatment regimen. Follow-up is conducted online through computerised assessment at baseline, 26, 52, 104 and 208 weeks. Participants receive automated reminders to log into their study portal and complete all assessments.
Primary outcome measure
Current primary outcome measure as of 23/07/2019:
Executive Function (Baddeley Grammatical Reasoning) measured through online assessment using the PROTECT online test battery at baseline, 26, 52, 104 and 156 weeks. This measure has been used to assess cognitive change in adults with AACD in a recent large online clinical trial (Corbett, et al. 2015a).
Previous primary outcome measure:
Executive Function (Baddeley Grammatical Reasoning) measured through online assessment using the validated cognitive assessment battery, CogTrack™, at baseline, 26, 52, 104 and 208 weeks
Secondary outcome measures
Current secondary outcome measures as of 23/07/2019:
The following outcomes were measured at the baseline, 26, 52, 104 and 156 weeks:
1. Full PROTECT Cognitive Test Battery (Reaction time, Attentional Indices, Paired Associate Learning, Digit Span and Self-Ordered Search Task, Digit Vigilance, Verbal Learning, Spatial Working Memory, Executive Function)
2. Instrumental Activities of Daily Living
3. EQ5D measure of health and wellbeing
4. Mild Behaviour Impairment Scale
Previous secondary outcome measures:
The following outcomes were measured at the baseline, 26, 52, 104 and 208 weeks:
1. Full PROTECT Cognitive Test Battery (PROTECT test battery (Digit Vigilance, Verbal Learning, Spatial Working Memory, Executive Function)
2. Full CogTrack™ test Battery (Reaction time, Attentional Indices, Paired Associate Learning, Digit Span and Self-Ordered Search Task)
3. Instrumental Activities of Daily Living
4. EQ5D measure of health and wellbeing
5. Mild Behaviour Impairment Scale
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. Aged 50 years and over
2. Already registered as a participant on the PROTECT study
3. Fulfilling the AACD criteria: performing at least standard deviation below age-matched population norms in two cognitive tests, as measured using the validated PROTECT and CogTrackTM online cognitive test batteries
4. Fulfilling criteria for vitamin D deficiency risk (defined by a self-reported scale to be completed upon registration (based on Annweiler et al., 2017)
5. Access to a computer and the internet
Target number of participants
Participant exclusion criteria
1. Diagnosed with dementia
2. Already participating in another active interventional clinical trial
3. Regularly taking any supplement containing vitamin D:
3.1. If the supplement is prescribed for a pre-existing condition, the participant will be excluded
3.2. If the supplement is bought over the counter, the participant will have the option of stopping the supplement and re-registering for the trial after a 28 day washout period
4. Prescribed the medication Digoxin (Lanoxin)
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
University of Exeter Medical School
St Luke's Campus University of Exeter
University of Exeter
Research Ethics and Governance Office
St Germans Road
JP Moulton Foundation
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Academic publication in peer-reviewed journal
Presentation at national / international conference
Lay report including online content and social media
Clinical report for primary care audience
IPD sharing statement:
The datasets generated during and/or analysed during the current study are/will be available upon request from Dr Anne Corbett (email@example.com) and Mrs Ellie Pickering (firstname.lastname@example.org). Fully anonymised study data will be available as composite cognitive scores and raw numerical scores for all other outcomes after publication of the trial outcomes (expected January 2023) for three years. Data access will require a data access application submitted to the PROTECT steering committee, which are reviewed and approved on a case-by-case basis. Consent from participants will be collected to enable anonymised data sharing for approved collaborators. The steering committee retains the right to refuse use of data in the event of conflict with overall PROTECT study core research.
Intention to publish date
Participant level data
Available on request
Basic results (scientific)