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The OPAL Study: Older People And n-3 Long-chain polyunsaturated fatty acids
ISRCTN ISRCTN72331636
DOI 10.1186/ISRCTN72331636
ClinicalTrials.gov identifier
EudraCT number
Public title The OPAL Study: Older People And n-3 Long-chain polyunsaturated fatty acids
Scientific title
Acronym OPAL
Serial number at source N/A
Study hypothesis 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.
Lay summary
Ethics approval Not provided at time of registration
Study design Randomised controlled trial
Countries of recruitment United Kingdom
Disease/condition/study domain Cognitive and retinal function
Participants - 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.
Participants - 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
Anticipated start date 01/03/2004
Anticipated end date 31/03/2007
Status of trial Completed
Patient information material Patient information on the various different aspects of the trial can be found on the website at: http://www.lshtm.ac.uk/msu/opal/information.html
Target number of participants 800
Interventions 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).
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
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
Sources of funding UK Food Standards Agency
Trial website http://www.lshtm.ac.uk/msu/opal/index.html
Publications 1. 2006 protocol on http://www.ncbi.nlm.nih.gov/pubmed/16945130
2. 2010 results in http://www.ncbi.nlm.nih.gov/pubmed/20410089
Contact name Dr  Alan  Dangour
  Address London School of Hygiene and Tropical Medicine
Keppel Street
  City/town London
  Zip/Postcode WC1E 7HT
  Country United Kingdom
  Tel +44 (0)20 7958 8133
  Fax +44 (0)20 7958 8111
  Email Alan.Dangour@lshtm.ac.uk
Sponsor Medical Research Council (UK)
  Address Dr Ian Viney
Stephenson House
158-160 North Gower Street
  City/town London
  Zip/Postcode NW1 2ND
  Country United Kingdom
  Tel +44 (0)20 7670 4625
  Fax +44 (0)20 7670 4890
  Email iv@centre-london.mrc.ac.uk
Date applied 27/05/2004
Last edited 27/04/2010
Date ISRCTN assigned 14/07/2004
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