LO MAPT is an 18-month, phase III, multicenter, randomized, placebo-controlled, 2 parallel groups trial, followed by a 18-month open-label extension phase, to evaluate the efficacy of omega-3 supplementation on cognitive decline in older adults with low DHA/EPA status and subjective memory complaints or family history of Alzheimer disease.

LO-MAPT will also assess the effect of an audiovisual aid, compared with traditional paper participant information sheet only, on participants' understanding of the protocol, as well as on drop-out, adherence and clinical outcome in older adults at risk of cognitive decline. In addition to the main LO-MAPT study procedures, in two centers, half of the subjects will receive an audiovisual aid in addition to the standard information sheet.

The primary objective of LO MAPT is to demonstrate the efficacy of a 18-month intervention with a supplementation of omega-3 (DHA+EPA) on cognitive decline as measured by a composite score of neuropsychological assessments in older adults with low DHA/EPA status (RBC DHA/EPA index ≤ 4.83%) and subjective memory complaints or family history of Alzheimer's disease.

Subjects will be randomly assigned in a 1:1 ratio to one of the following 2 groups: (i) DHA+EPA supplement or (ii) placebo. A computer-generated randomisation procedure will be used with stratification by centre. A centralised Interactive Voice Response System will be used to identify which group to allocate and which lot number to administer. A document describing the randomization procedure will be kept confidentially by the Methodology and Data Management Centre. All participants and study staff will be blinded to DHA+EPA supplement/placebo assignment: all participants will receive soft capsules of exactly the same appearance and taste.

Inclusion Criteria:

• RBC DHA/EPA index ≤ 4.83% with at least one of the following criteria:
• subjective memory complaint,
• family history of Alzheimer's disease;
• Mini-Mental State Examination (MMSE) score ≥ 24;
• Have a study partner that is willing to participate as a source of information and has at least weekly contact with the participant (contact can be in person, via telephone or electronic communication);
• Sufficient vision and hearing to complete study protocol procedures based on medical judgment;
• Have general health status that will not interfere with the ability to complete the study;
• Willing and able to participate and to give written consent to comply with study procedures;
• Covered by a health insurance system.

Exclusion Criteria:

• Criteria related to diseases:
• Known presence of dementia or Alzheimer's disease (DSMIV criteria);
• Dependency for basic activities of daily living (ADL score <4);
• Presence of serious diseases, which could be life-threatening in the short term.
• Criteria related to treatments:
• Taking of supplements containing omega-3 (apart from food) within the past 6 months and/or taking omega-3 at inclusion.
• Criteria related to subjects:
• Visual or hearing impairments incompatible with performance and/or interpretation of the neuropsychological tests;
• History or presence of any previous condition (severe depression or generalized anxiety) that could, in the opinion of the investigator, interfere with the results of the study or expose the subject to an additional risk;
• Subjects deprived of their liberty by administrative or judicial decision, or under guardianship or admitted to a healthcare or social institution (subjects in non-assisted living facilities could be recruited);
• Participation in another clinical study in the previous month or participation scheduled during the study;
• Food allergy.

This study will be a double-blind trial. The packaging, presentation, and labelling of products will ensure the blinding of both the medical team and the patient. The treatment arms in this study will be differentiated only by treatment numbers. Treatment arms will be allocated treatment numbers according to the previously established randomisation table.

Neither the investigating doctors nor the patients will be aware of the treatment arm to which the patients have been allocated until the end of the study.