Relationship between education and age-related cognitive decline: a review of recent research.

The association between level of educational attainment and cognitive performance is well studied. People with higher education perform better across a broad range of cognitive tasks. However, there is uncertainty as to whether education moderates the trajectory of age-related cognitive decline. This review paper addresses the potential link between education and age-related cognitive decline by evaluating relevant research published since 2000. Studies reporting data on education and its association with the rate of cognitive decline across various cognitive domains were reviewed. A total of 10 studies were identified with a mean follow-up period of 7.6 years; each contained a population-based, non-demented sample. In the majority of studies, results showed that education did not moderate age-associated cognitive decline. The few studies that did find an association between education and decline in specific cognitive functions should be interpreted with caution because of methodological issues. The literature reveals little consistent evidence that normal age-related cognitive decline is moderated by education attainment. This supports a passive theory of cognitive reserve: people with a higher level of education will continue to perform at a higher level of cognitive functioning than their lower educated peers, which may delay the onset of impairment in the future.

Exploring the validity of mild cognitive impairment (MCI) subtypes: multiple-domain amnestic MCI is the only identifiable subtype at longitudinal follow-up.

BACKGROUND: Epidemiological research exploring risk factors for Alzheimer's dementia resulted in the identification of the mild cognitive impairment (MCI) profile. Subsequently, distinct subtypes of MCI have been proposed; however, the validity of these as diagnostic entities remains uncertain. DESIGN AND PARTICIPANTS: The aim of the present study was to examine the longitudinal neuropsychological profiles of MCI subtypes. A total of 118 adults aged 60-90 years were classified at screening as amnestic (a-MCI), nonamnestic (na-MCI), and multiple-domain amnestic (a-MCI+) and were assessed at two time points across 20 months on a comprehensive neuropsychological assessment battery. RESULTS: The a-MCI+ group displayed the poorest performance of all groups in terms of episodic memory, working memory, attention, and executive functioning. CONCLUSIONS: These findings suggest that the a-MCI+ subtype is the only variant that is recognizable via neuropsychological testing. In contrast, the differentiation between single-domain subtypes and healthy controls is difficult and may not be achievable through current neuropsychological assessment practices.

BDNF and COMT polymorphisms have a limited association with episodic memory performance or engagement in complex cognitive activity in healthy older adults.

Cognitive decline is a major factor in lowering the quality of life in older populations, and contributes substantially to social, economic, and health costs. As humans age, cognitive function decreases differentially, and individual differences in cognitive ageing are likely attributed to a range of causes, including environmental and genetic influences. The current study included 360 participants (240 females and 120 males) aged between 50 and 79years from the Tasmanian Healthy Brain Project. The brain-derived neurotrophic factor (BDNF) Val66Met and Catechol-O-Methyltransferase (COMT) Val158Met polymorphisms were examined for their association with visual and auditory episodic memory performance. The polymorphisms were also investigated for their association with reported life-long engagement in complex cognitive activity using a retrospective questionnaire. Relative to the demographic variables, the gene variations were found to have no association with episodic memory performance, with the exception of the COMT polymorphism on a single measure of auditory memory (RAVLT). Several other studies also demonstrated that these polymorphisms have no, small, or inconsistent effects on memory function. The BDNF Val66Met and COMT Val158Met polymorphisms were also found to be of little significance to active engagement in complex cognitive activity throughout most of the lifespan. An association was detected between BDNF Val66Met and engagement in cognitive activity in early life (p=.04, d=.23), however this did not reach significance when adjusted for multiple comparisons. The biological mechanisms that underlie engagement in cognitive activity are elusive, thus the potential relationship between BDNF Val66Met genotype and early life cognitive engagement warrants further investigation.

The self-fulfilling prophecy of episodic memory impairment in mild cognitive impairment: do episodic memory deficits identified at classification remain evident when later examined with different memory tests?

Previous studies of mild cognitive impairment (MCI) have been criticised for using the same battery of neuropsychological tests during classification and longitudinal followup. The key concern is that there is a potential circularity when the same tests are used to identify MCI and then subsequently monitor change in function over time. The aim of the present study was to examine the evidence of this potential circularity problem. The present study assessed the memory function of 72 MCI participants and 50 healthy controls using an alternate battery of visual and verbal episodic memory tests 9 months following initial comprehensive screening assessment and MCI classification. Individuals who were classified as multiple-domain amnestic MCI (a-MCI+) at screening show a significantly reduced performance in visual and verbal memory function at followup using a completely different battery of valid and reliable tests. Consistent with their initial classification, those identified as nonamnestic MCI (na-MCI) or control at screening demonstrated the highest performance across the memory tasks. The results of the present study indicate that persistent memory deficits remain evident in amnestic MCI subgroups using alternate memory tests, suggesting that the concerns regarding potential circularity of logic may be overstated in MCI research.

Absence of a relationship between subjective memory complaint and objective memory impairment in mild cognitive impairment (MCI): is it time to abandon subjective memory complaint as an MCI diagnostic criterion?

BACKGROUND: Subjective memory complaints are a requirement in the diagnosis of mild cognitive impairment (MCI) as they are thought to indicate a decline in objective memory performance. However, recent research suggests that the relationship between subjective memory complaint and objective memory impairment is less clear. Thus, it is possible that many people without subjective memory complaints who develop Alzheimer's disease are precluded from a diagnosis of MCI. METHODS: The present study examined the relationship between subjective memory complaint assessed using the Multifactorial Memory Questionnaire (MMQ) and objective memory impairment assessed using standard neuropsychological measures in cases of amnestic MCI (n = 48), non-amnestic MCI (n = 27), and unimpaired healthy participants (n = 64). RESULTS: Correlational and regression analyses indicated that subjective memory complaints displayed a poor relationship with objective memory performance. A subsequent discriminant function analysis indicated that subjective memory complaints failed to improve the diagnostic accuracy of MCI and resulted in increased rates of false negative and false positive diagnoses. CONCLUSION: The results of the present study suggest that a diagnostic criterion of subjective memory complaint reduces the accuracy of MCI diagnosis, resulting in an elevated rate of false positive and false negative diagnoses. The results of this study in conjunction with recent research indicate that a criterion of subjective memory complaint should be discarded from emerging diagnostic criteria for MCI.