Docosahexaenoic acid (DHA) is a long-chain omega-3 polyunsaturated fatty acid essential for maintaining optimal brain and cardiometabolic health across adulthood and aging. Despite its biological relevance, global evidence indicates substantial variability in DHA intake and status, largely influenced by dietary patterns, food availability, and socioeconomic conditions. This narrative review synthesized observational and interventional studies published between 2014 and 2026 that evaluated DHA intake or biomarkers in adults and older adults, emphasizing disparities according to country income level. Studies were categorized following the World Bank Gross National Income (GNI) classification and analyzed to describe intake patterns, biochemical concentrations, and their reported health associations. Important inequities were observed between countries. Populations in high-income countries (HICs) generally reported higher DHA intake and tissue concentrations, mainly due to regular fish consumption and greater access to supplementation, while evidence from middle-income countries (MICs) was scarce, heterogeneous, and based on small non-representative samples. In HICs, even moderate fish intake significantly improved DHA status, whereas in MICs, mean intakes frequently fell below 200 mg/day, a threshold commonly associated with cardiometabolic and neurocognitive benefits. Higher DHA levels were consistently linked to more favorable lipid profiles, lower triglyceride concentrations, and better cardiovascular indicators, though associations with blood pressure and mortality were inconsistent. Evidence from neurocognitive studies suggested structural and functional advantages, including larger total brain volume, improved white matter integrity, and enhanced cognitive performance, yet findings on memory and dementia outcomes remain inconclusive. Overall, this narrative review highlights global inequities in DHA intake and data availability, particularly in MICs, where natio
Okai-Mensah ( 47 ), 2025, United Kingdom High income Narrative review Adults and older adults Evidence synthesized from human observational studies, randomized controlled trials, and mechanistic studies Cardiometabolic health DHA intake discussed qualitatively from dietary sources and
De Oliveira Otto ( 54 ), 2018, United States High income Prospective cohort study Community-dwelling adults from the ARIC cohort, free of dementia at baseline. Cognition and mental health Biomarkers: Plasma phospholipid DHA (% of total fatty acids), analyzed in quintiles and per interquartile range (IQR). Dietary intake: Not used as primary exposure. Cognitive decline (3MSE): No significant association ( β for annual change −0.03; p = 0.28). Incident cognitive impairment: No significant association across DHA quintiles (Q5 vs. Q1 HR 0.80; p-trend = 0.21); Total dementia: No significant association across DHA quintiles (Q5 vs.
Lewis ( 45 ), 2025, United Kingdom High income Narrative review Adults and older adults. Evidence summarized from human observational studies, randomized controlled trials, and mechanistic studies Cognition and Mental Health Dietary intake: DHA intake is discussed qualitatively from dietary sources and supplementation; no pooled or population-representative intake values are reported. Biomarkers: DHA status is described using plasma phospholipids, erythrocytes, cerebrospinal fluid, and brain tissue DHA levels from cited studies. Endogenous conversion from ALA is reported as minimal (<1%), with tissue DHA levels depending mainly on preformed DHA intake.
Macaron ( 42 ), 2021, Multiple countries High income Narrative review Cognitively healthy adults aged ≥45 years, including middle-aged and older adults; non-demented, free of neurological or psychiatric disease. Cognition and Mental Health No original data. The review summarizes studies assessing dietary DHA intake and blood DHA biomarkers (plasma phospholipid DHA and erythrocyte DHA), either individually or as part of omega-3 measures, depending on the primary study Across the studies summarized, higher DHA intake or higher blood DHA levels were most frequently associated with better cognitive performance and greater brain structural integrity in adults and older adults.
Mohajeri ( 40 ), 2015, Multiple countries High income Narrative review Adults and older adults; cognitively normal adults and individuals with age-related cognitive decline (review of human observational and intervention studies) Cognition and Mental Health No original dietary intake data or biomarker measurements are reported. The review synthesizes evidence from studies assessing dietary DHA intake, plasma DHA, erythrocyte DHA, and brain DHA content, depending on study design. DHA is discussed independently from EPA in several of the summarized studies, particularly those focused on brain structure and function.
The review also notes that intervention trials show mixed results, with benefits more consistently observed in individuals with low baseline DHA status or early cognitive changes, and no causal conclusions are established. Natacci ( 72 ), 2018, Brazil Upper middle income Cross-sectional analysis (baseline data from a population-based cohort: ELSA-Brasil) Adults aged 35–74 years Final analytical sample: 12,268 participants Cognition and Mental Health Dietary intake assessed using a validated 114-item FFQ. DHA intake was quantified in g/day and analyzed in quintiles, adjusted for total energy intake.
Román ( 37 ), 2019, Spain High income Narrative review Adults and older adults; human studies including cognitively healthy individuals and populations with cognitive impairment (review of observational and intervention studies) Cognition and Mental Health The review does not report original dietary intake data or biomarker measurements. It summarizes evidence from human studies evaluating dietary DHA intake, plasma DHA, erythrocyte DHA, and brain DHA levels, depending on the study cited.
K, Finn AS, Mabbott DJ (August 2020). "Children's family income is associated with cognitive function and volume of anterior not posterior hippocampus"
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, it would be impossible for language, relationships, or personal identity to develop. Memory loss is usually described as forgetfulness or a disorder such as am
Cognitive neuroscientists consider memory as the retention, reactivation, and reconstruction of the experience-independent internal representation. The term of internal representation implies that such a definition of memory contains two components: the expression of memory at the behavioral or conscious level, and the underpinning physical neural changes (Dudai 2007). The latter component is also called engram or memory traces (Semon 1904). Some…
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It is out of cognitive control and is an automatic response. With very short presentations, participants often report that they seem to "see" more than they can actually report. The first precise experiments exploring this form of sensory memory were conducted by George Sperling (1963) using the "partial report paradigm." Subjects were presented with a grid of 12 letters, arranged into three rows of four. After a brief presentation, subjects were then played either a high, medium or low tone, cuing them which of the rows to report.
Short-term memory is supported by transient patterns of neuronal communication, dependent on regions of the frontal lobe (especially dorsolateral prefrontal cortex) and the parietal lobe. Long-term memory, on the other hand, is maintained by more stable and permanent changes in neural connections widely spread throughout the brain. The hippocampus is essential (for learning new information) to the consolidation of information from short-term to long-term memory, although it does not seem to store information itself.
The term of internal representation implies that such a definition of memory contains two components: the expression of memory at the behavioral or conscious level, and the underpinning physical neural changes (Dudai 2007). The latter component is also called engram or memory traces (Semon 1904). Some neuroscientists and psychologists mistakenly equate the concept of engram and memory, broadly conceiving all persisting after-effects of experiences as memory; others argue against this notion that memory does not exist until it is revealed in behavior or thought (Moscovitch 2007).
One question that is crucial in cognitive neuroscience is how information and mental experiences are coded and represented in the brain. Scientists have gained much knowledge about the neuronal codes from the studies of plasticity, but most of such research has been focused on simple learning in simple neuronal circuits; it is considerably less clear about the neuronal changes involved in more complex examples of memory, particularly declarative memory that requires the storage of facts and events (Byrne 2007). Convergence-divergence zones might be the neural networks where memories are stored and retrieved.
PKMζ maintains the activity-dependent enhancement of synaptic strength and inhibiting PKMζ erases established long-term memories, without affecting short-term memory or, once the inhibitor is eliminated, the ability to encode and store new long-term memories is restored. Also, BDNF is important for the persistence of long-term memories. The long-term stabilization of synaptic changes is also determined by a parallel increase of pre- and postsynaptic structures such as axonal bouton, dendritic spine and postsynaptic density.
glucocorticoids and catecholamines) which affect memory encoding processes in the hippocampus. Behavioural research on animals shows that chronic stress produces adrenal hormones which impact the hippocampal structure in the brains of rats. An experimental study by German cognitive psychologists L. Schwabe and O. Wolf demonstrates how learning under stress also decreases memory recall in humans. In this study, 48 healthy female and male university students participated in either a stress test or a control group.
The more long term the exposure to stress is, the more impact it may have. However, short term exposure to stress also causes impairment in memory by interfering with the function of the hippocampus. Research shows that subjects placed in a stressful situation for a short amount of time still have blood glucocorticoid levels that have increased drastically when measured after the exposure is completed. When subjects are asked to complete a learning task after short term exposure they often have difficulties.
Prenatal stress also hinders the ability to learn and memorize by disrupting the development of the hippocampus and can lead to unestablished long term potentiation in the offspring of severely stressed parents. Although the stress is applied prenatally, the offspring show increased levels of glucocorticoids when they are subjected to stress later on in life. One explanation for why children from lower socioeconomic backgrounds tend to display poorer memory performance than their higher-income peers is the effects of stress accumulated over the course of the lifetime.
No long-term follow-up was conducted; it is therefore unclear if this intervention has lasting effects on memory. Exercise, even at light intensity, significantly improves memory across all age groups, with the greatest benefits observed in children and adolescents. Even low- to moderate-intensity exercise and shorter interventions (1–3 months) can produce meaningful cognitive improvements. There are a loosely associated group of mnemonic principles and techniques that can be used to vastly improve memory known as the art of memory.
ERIC - EJ1183121 - Income Gains Predict Cognitive Functioning Longitudinally throughout Later Childhood in Poor Children, Developmental Psychology, 2018-Jul Notes FAQ Contact Us Collection Thesaurus Advanced Search Tips Peer reviewed only Full text available on ERIC Collection Thesaurus Browse Thesaurus Include Synonyms Include Dead terms Peer reviewed Direct link ERIC Number: EJ1183121 Record Type: Journal Publication Date: 2018-Jul Pages: 12 Abstractor: As Provided ISBN: N/A ISSN: ISSN-0012-1649 EISSN: N/A Available Date: N/A Income Gains Predict Cognitive Functioning Longitudinally throughout Later Childhood in Poor Children Raffington, Laurel; Prindle, John J.; Shing, Yee Lee Developmental Psychology , v54 n7 p1232-1243 Jul 2018 Alleviating disadvantage in low-income environments predicts higher cognitive abilities during early childhood.
It is less established whether family income continues to predict cognitive growth in later childhood or whether there may even be bidirectional dynamics. Notably, living in poverty may moderate income-cognition dynamics. In this study, we investigated longitudinal dynamics over 7 waves of data collection from 1,168 children between the ages of 4.6 and 12 years, 226 (19%) of whom lived in poverty in at least 1 wave, as part of the NICHD Study of Early Child Care and Youth Development. Two sets of dual change-score models evaluated, first, whether a score predicted change from that wave to the next and, second, whether change from 1 wave to the next predicted the following score.
As previous comparisons have documented, poor children had substantially lower average starting points and cognitive growth slopes through later childhood. The first set of models showed that income scores did not predict cognitive change. In reverse, child cognitive scores positively predicted income change. We speculated that parents may reduce their work investment, thus reducing income gains, when their children fall behind.
Second, income changes continued to positively predict higher cognitive scores at the following wave for poor children only, which suggests that income gains and losses continue to be a leading indicator in time of poor children's cognitive performance in later childhood. This study underlined the need to look at changes in income, allow for poverty moderation, and explore bidirectional income--cognition dynamics in middle childhood.
Descriptors: Poverty , Cognitive Development , Scores , Prediction , Disadvantaged , Cognitive Ability , Child Development , Family Income , Longitudinal Studies , Preschool Children , Children , Correlation , Change , Statistical Analysis , Achievement Tests , Cognitive Tests , Mothers , Educational Attainment , Mathematics Skills , Verbal Ability , Regression (Statistics) American Psychological Association. Journals Department, 750 First Street NE, Washington, DC 20002.
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