Long-term omega-3 supplementation was associated with a 64% lower risk of Alzheimer's disease in observational data from the Alzheimer's Disease Neuroimaging Initiative cohort of older adults followed for up to 6 years. However, these observational findings cannot establish causation, and randomized controlled trials have shown mixed results.
A companion review of 48 longitudinal studies found that higher dietary omega-3 intake—particularly DHA and EPA—was linked with lower risk of dementia or cognitive decline across 103,651 participants.
In the Alzheimer's Disease Neuroimaging Initiative study, 1,135 participants without dementia (mean age, 73 years) were evaluated for incident Alzheimer's disease. Long-term supplement use (10 years or more) showed the strongest associations, particularly among carriers of apolipoprotein E (APOE) ε4, older adults, and participants with mild cognitive impairment.
In dose-response analyses, each 0.1 g/day increase in DHA or EPA intake corresponded to about an 8%-10% lower risk of cognitive decline, with risk reduction becoming more apparent when intake exceeded roughly 1 g/day. Higher plasma EPA and erythrocyte DHA levels were also associated with lower cognitive decline risk.
The researchers reported no conflicts of interest.