Condition category
Mental and Behavioural Disorders
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
No longer recruiting

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

When is the study starting and how long is it expected to run for?
June 2018 to February 2022

Who is funding the study?
JP Moulton Foundation (UK)

Who is the main contact?
Dr Anne Corbett

Trial website

Contact information



Primary contact

Dr Anne Corbett


Contact details

South Cloister's
St Luke's Campus
University of Exeter Medical School
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

A randomised clinical trial of vitamin D to improve cognition in people at risk of dementia



Study hypothesis

Vitamin D supplementation will confer benefit to cognition in adults with AACD compared to placebo

Ethics approval

Pending - ethical approval is expected to be gained by November 2018

Study design

An interventional double-blind placebo-controlled two-arm single-centre randomised controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet



Age-Associated Cognitive Decline


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.

Intervention type



Drug names

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

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 (Annweiler et al., 2017)
5. Access to a computer and the internet

Participant type

Healthy volunteer

Age group




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

United Kingdom

Trial participating centre

University of Exeter Medical School
St Luke's Campus University of Exeter
United Kingdom

Sponsor information


University of Exeter

Sponsor details

Research Ethics and Governance Office
Lafrowda House
St Germans Road
United Kingdom

Sponsor type




Funder type

Not defined

Funder name

JP Moulton Foundation

Alternative name(s)

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 ( and Mrs Ellie Pickering ( 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)

Publication list

Publication citations

Additional files

Editorial Notes