Omega 3 fatty acid for the prevention of cognitive decline and dementia

Abstract

BACKGROUND: Evidence from observational studies suggests that diets high in omega-3 long-chain polyunsaturated fatty acids (PUFA) may protect people from cognitive decline and dementia. The strength of this potential protective effect has recently been tested in randomized controlled trials. OBJECTIVES: To assess the effects of omega-3 PUFA supplementation for the prevention of dementia and cognitive decline in cognitively healthy older people. METHODS:Search: We searched ALOIS -the Cochrane Dementia and Cognitive Improvement Group's Specialized Register on -6 April 2012 using the terms: "omega 3", PUFA, "fatty acids", "fatty acid", fish, linseed, eicosapentaenoic, docosahexaenoic. Selection criteria: Randomised controlled trials of an omega-3 PUFA intervention which was provided for a minimum of six months to participants aged 60 years and over who were free from dementia or cognitive impairment at the beginning of the study. Two review authors independently assessed all trials. Data collection and analysis:The review authors sought and extracted data on incident dementia, cognitive function, safety and adherence, either from published reports or by contacting the investigators for original data. Data were extracted by two review authors. We calculated mean difference (MD) or standardised mean differences (SMD) and 95% confidence intervals (CI) on an intention-to-treat basis, and summarized narratively information on safety and adherence. MAIN RESULTS: Information on cognitive function at the start of a study was available on 4080 participants randomised in three trials. Cognitive function data were available on 3536 participants at final follow-up. In two studies participants received gel capsules containing either omega-3 PUFA (the intervention) or olive or sunflower oil (placebo) for six or 24 months. In one study, participants received margarine spread for 40 months; the margarine for the intervention group contained omega-3 PUFA. Two studies had cognitive health as their primary outcome; one study of cardiovascular disease included cognitive health as an additional outcome. None of the studies examined the effect of omega-3 PUFA on incident dementia. In two studies involving 3221 participants there was no difference between the omega-3 and placebo group in mini-mental state examination score at final follow-up (following 24 or 40 months of intervention); MD-0.07 (95% CI -0.25 to 0.10). In two studies involving 1043 participants, other tests of cognitive function such as word learning, digit span and verbal fluency showed no beneficial effect of omega-3 PUFA supplementation. Participants in both the intervention and control groups experienced either small or no cognitive declines during the studies. The main reported side-effect of omega-3 PUFA supplementation was mild gastrointestinal problems. Overall, minor adverse events were reported by fewer than 15% of participants, and reports were balanced between intervention groups. Adherence to the intervention was on average over 90% among people who co...

Association of fish oil supplement use with preservation of brain volume and cognitive function

“…Although a number of prospective cohort studies have identified positive associations between consumption of fatty fish and better cognitive health in long-term follow-up, the effects of supplemented fish oils or DHA have been studied in controlled trials for much shorter periods, up to 18 months in populations with dementia or MCI and 24 months in the cognitively normal elderly [9,16]. The predominance of ADNI participants using FOSs for unusually long periods was unexpected but provided a unique opportunity to study multiple clinical outcomes during long periods of exposure to supplemented n-3 PUFAs.…”

“…Although observational studies have generally reported better cognitive functioning or lower rates of incident Alzheimer’s disease (AD) in populations reporting greater dietary intake of fatty fish, but with few exceptions [2–8], the results of placebo-controlled trials of 3- to 24-month treatment with DHA or DHA + EPA have not supported these findings [9–12]. Treatment with n-3 PUFAs has been ineffective in controlled trials of mild-to-moderate AD [13–16]; however, there is some evidence that intervening in very mild AD or mild cognitive impairment (MCI) may be beneficial [8,14,17,18].…”

Very long chain omega‐3 (n‐3) fatty acids and human health

“…Some studies have linked low blood levels of very long chain n‐3 fatty acids to dementia and cognitive impairment . However, a Cochrane review of RCTs studying the role of very long chain n‐3 fatty acids in preventing cognitive decline in healthy older people showed no benefits . Sinn et al reported that 1.8 g EPA + DHA/day for 6 months reduced depressive symptoms and improved cognition in adults with mild cognitive impairment.…”

“…Interestingly many of these studies are indicative that EPA is more important than DHA, which contrasts with the relative roles of the fatty acids in very early eye and brain development. Although there may be a role for very long chain n‐3 fatty acids in slowing cognitive decline, this has not yet been well demonstrated .…”

Oxidant/Antioxidant Imbalance and the Risk of Alzheimer's Disease

“…The action of NPD1 includes up regulation of Bcl-2 family, down regulation of pro-apoptotic proteins and suppressing the production of prostaglandin that participated in neuronal damage. Furthermore, there is a growing body of evidence that DHA modifies the expression of many genes that regulate a variety of biological functions including neurogenesis and neuronal functions and survival that important for cognitive health [138]. Thus, the intake of DHA can reduced the risk of AD [139].…”