The OPAL Study: Older People And n-3 Long-chain polyunsaturated fatty acids

ISRCTN	ISRCTN72331636
DOI	https://doi.org/10.1186/ISRCTN72331636
Protocol serial number	N/A
Sponsor	Medical Research Council (UK)
Funder	UK Food Standards Agency

Submission date: 27/05/2004
Registration date: 14/07/2004
Last edited: 27/04/2010

Recruitment status: No longer recruiting
Overall study status: Completed
Condition category: Eye Diseases

Prospectively registered

Protocol

Statistical analysis plan

Results

Individual participant data

Plain English summary of protocol

Not provided at time of registration

Contact information

Dr Alan Dangour
Scientific

London School of Hygiene and Tropical Medicine
Keppel Street
London
WC1E 7HT
United Kingdom

Phone	+44 (0)20 7958 8133
Email	Alan.Dangour@lshtm.ac.uk

Study information

Primary study design	Interventional
Study design	Randomised controlled trial
Secondary study design	Randomised controlled trial
Study type	Participant information sheet
Scientific title
Study acronym	OPAL
Study objectives	There is considerable interest in the hypothesis that improving the diet of older people, specifically increasing the dietary intake of n-3 long-chain polyunsaturated fatty acids (n-3 LCPs) may be able to delay the initiation, or slow the progression, of cognitive decline. To date, there has been little attention given to the possible protective role of n-3 LCPs in age-related loss of cognitive or retinal function. OPAL is a double-blind randomised placebo-controlled trial carried out among adults aged 70-79 years in the UK. The intervention arm will receive a daily capsule containing 700 mg n-3 LCP (both decosahexaenoic acid DHA and eicosapentaenoic acid EPA) while the placebo arm will receive a daily capsule containing olive oil. The main outcome variable assessed at 24 months will be cognitive performance and a second major outcome variable will be retinal function. Retinal function tests are included as the retina is a specifically differentiated neural tissue and therefore represents an accessible window into the functioning of the brain. The overall purpose of this public-health research is to help define a simple and effective dietary intervention aimed at maintaining cognitive and retinal function in later life. This is the first trial of its kind aiming to slow the decline of cognitive and retinal function in older people by increasing daily dietary intake of n-3 LCPs. The link between cognitive ability, visual function and quality of life among older people suggests that this novel line of research may have considerable public health importance. Study hypotheses: 1. For healthy, cognitively normal adults aged 70-79 years of age, daily supplementation with n-3 LCPs (500 mg DHA and 200 mg EPA) will slow the rate, or delay the onset, of cognitive decline. 2. For healthy, cognitively normal adults aged 70-79 years of age, daily supplementation with n-3 LCPs (500 mg DHA and 200 mg EPA) will improve visual function by enhancing rod photoreceptor response to light and visual-cortical integration.
Ethics approval(s)	Not provided at time of registration
Health condition(s) or problem(s) studied	Cognitive and retinal function
Intervention	Daily nutritional supplement of 0.7 g of n-3 long chain polyunsaturated fatty acids (fish oil) versus placebo. The main outcome variable assessed at 24 months will be cognitive performance and a second major outcome variable will be retinal function (Moorfields Eye Hospital will undertake retinal testing in a sub group).
Intervention type	Other
Primary outcome measure(s)	1. Change in cognitive function at 24 months determined by the California Verbal Learning Test 2. Change in rod sensitivity over 24 months of intervention as measured by electroretinogram
Key secondary outcome measure(s)	1. Cognitive performance as measured by immediate and delayed recall of a short story, tests of prospective memory, timed letter search/cancellation task, verbal fluency, digit span backwards, symbol digit modalities test, simple and choice reaction time, dual-task performance and spatial memory 2. Blood pressure 3. Measure of depression 4. Change in Body Mass Index 5. Compliance determined by counting the number of tablets remaining every 3 months, and by measuring the change in n-3 LCP concentration in buccal epithelial cells over 24 months 6. Number of hospital admissions for cardiovascular events over 24 months 7. Death 8. Colour vision measured by detecting sensitivity to colour contrast which is a good marker of central retinal function 9. Eye health assessed by carrying out a full ophthalmic examination
Completion date	31/03/2007

Eligibility

Participant type(s)	Healthy volunteer
Age group	Senior
Sex	Not Specified
Target sample size at registration	800
Key inclusion criteria	Healthy volunteers aged between 70-79 years of age, who have no previous history of diabetes or dementia. Participants will be selected from 20 GP practices.
Key exclusion criteria	1. Pre-existing type I or type II diabetes at baseline 2. Pre-existing dementia at baseline 3. Reported daily use of fish-oil supplements (in liquid or capsule form) at baseline 4. Mini-mental state examination (MMSE) score <24 at baseline screen
Date of first enrolment	01/03/2004
Date of final enrolment	31/03/2007

Locations

Countries of recruitment

United Kingdom
England

Study participating centre

London School of Hygiene and Tropical Medicine

London
WC1E 7HT
United Kingdom

Results and Publications

Individual participant data (IPD) Intention to share	No
IPD sharing plan summary	Not provided at time of registration
IPD sharing plan

Study outputs

Output type	Details	Date created	Date added	Peer reviewed?	Patient-facing?
Results article	results	01/06/2010		Yes	No
Protocol article	protocol	31/08/2006		Yes	No
Participant information sheet	Participant information sheet	11/11/2025	11/11/2025	No	Yes
Study website	Study website	11/11/2025	11/11/2025	No	Yes