Rate of memory decline in AD is related to education and occupation: cognitive reserve?

Concept of functional imaging of memory decline in Alzheimer's disease

Functional imaging methods such as Positron Emission Tomography (PET) and functional Magnetic Resonance Imaging (fMRI) have contributed inestimably to the understanding of physiological cognitive processes in the brain in the recent decades. These techniques for the first time allowed the in vivo assessment of different features of brain function in the living human subject. It was therefore obvious to apply these methods to evaluate pathomechanisms of cognitive dysfunction in disorders such as Alzheimer's disease (AD) as well. One of the most dominant symptoms of AD is the impairment of memory. In this context, the term "memory" represents a simplification and summarizes a set of complex cognitive functions associated with encoding and retrieval of different types of information. A number of imaging studies assessed the functional changes of neuronal activity in the brain at rest and also during performance of cognitive work, with regard to specific characteristics of memory decline in AD. In the current article, basic principles of common functional imaging procedures will be explained and it will be discussed how they can be reasonably applied for the assessment of memory decline in AD. Furthermore, it will be illustrated how these imaging procedures have been employed to improve early and specific diagnosis of the disease, to understand specific pathomechanisms of memory dysfunction and associated compensatory mechanisms, and to draw reverse conclusions on physiological function of memory.

Applicability of neural reserve theory in mild traumatic brain injury

OBJECTIVE

The aim of the current study was to examine whether neural reserve influenced the duration of post-traumatic amnesia (PTA) following mild traumatic brain injury (MTBI).

METHOD

The relationship between duration of PTA and both IQ and education was examined in a group of 59 MTBI patients. In addition, the effects of factors that could potentially diminish neural reserve, namely pre-injury hazardous alcohol consumption, pre-injury marijuana use, previous neurological damage, age and post-injury emotional distress on PTA duration were analysed.

RESULTS

Significant, negative associations between PTA duration and both IQ and education were revealed. None of the other variables that were examined were significantly related to PTA duration.

CONCLUSION

The findings were interpreted as providing preliminary evidence to suggest that reference to neural reserve may help explain between-subject variability in acute response to MTBI.

Pattern and progression of cognitive decline in Alzheimer's disease: role of premorbid intelligence and ApoE genotype

BACKGROUND/AIMS

Because of controversial results across studies, we evaluated the predictive value of premorbid intelligence and the apolipoprotein E (ApoE) genotype on baseline and progression of cognitive performance in Alzheimer's disease (AD).

METHODS

Eighty-five mild AD cases, ApoE genotyped and included in a longitudinal cliniconeuropsychological-genetic study, underwent a premorbid intelligence test and up to 11 (average 5) neuropsychological assessments. We applied linear- and logistic-regression models for cross-sectional data and mixed models for longitudinal ones.

RESULTS

Higher premorbid intelligence was associated with higher global, executive and memory performance, while the ApoE epsilon 4 allele was specifically related to poorer memory performance. The premorbid intelligence-ApoE epsilon 4/epsilon 4 interaction was significant, with higher premorbid intelligence scores reducing the detrimental effect of ApoE epsilon 4 homozygosity on memory performance. Higher premorbid intelligence, but not the ApoE epsilon 4 allele, was related to faster memory deficit progression.

CONCLUSION

The association of higher premorbid intelligence with better baseline cognitive performance and faster memory decline, as well as its interaction with the ApoE genotype, strengthens the role of cognitive reserve in shaping the disease's clinical expression. Our findings confirm that the epsilon 4 allele affects memory deficit at baseline but does not exert any influence on the rate of cognitive decline.

Education and use of dementia drugs: a register-based study of over 600,000 older people

BACKGROUND/AIMS

Low education has been shown to be a risk factor for dementia. However, little is known about the association between educational level and dementia drugs.

METHODS

We conducted a register-based study in Sweden of 645,973 people aged 75-89 years. Data on age, sex, type of residential area (urban/rural), dispensed drugs and education were analyzed from people aged 75-89 years registered in the Swedish Prescribed Drug Register during July to October 2005. The 3 main outcome measures were dispensed dementia drugs, cholinesterase inhibitors (donepezil, rivastigmine and galantamine) and memantine.

RESULTS

Dementia drugs were used by 3% of the study population, cholinesterase inhibitors by almost 3% and memantine by 0.4%. High education was associated with dementia drugs (OR: 1.26; 95% CI: 1.19-1.34 for >or=15 years of education compared with <or=9 years), cholinesterase inhibitors (OR: 1.25; 95% CI: 1.17-1.33 for >or=15 years of education compared with <or=9 years) and, especially, memantine (OR: 1.46; 95% CI: 1.26-1.68 for >or=15 years of education compared with <or=9 years), after adjustment for age, sex, type of residential area and number of dispensed drugs.

CONCLUSION

The results indicate that there may be inequalities in the use of dementia drugs among elderly Swedes. Future research is required to explain why educational level has the opposite relationship to dementia drugs than to dementia diagnosis.

Cognitive decline and survival in Alzheimer's disease according to education level

OBJECTIVE

We tested the hypothesis that a higher education level is associated with faster cognitive decline and lower survival in a cohort of 670 Alzheimer's disease patients, followed for 3.5 years at the Lille-Bailleul memory centre.

METHODS

The patients were categorized in 3 groups according to educational levels: low (<or=8 years), intermediate (9-12 years) and high (>12 years). Cognitive function was measured with the Mini Mental State Examination (MMSE) and the Mattis Dementia Rating Scale (DRS). Survival was analyzed with a Cox model. Analyses were adjusted for age, sex, cholinesterase inhibitor treatment, diabetes, hypertension, visible vascular lesions on MRI, baseline DRS and MMSE.

RESULTS

The adjusted mixed random model showed that MMSE declined faster for patients with high and intermediate educational levels compared with those with a low educational level (p < 0.0001). The mean annually adjusted DRS decline was highest for the groups with the most education (p = 0.05). The mortality risk was not higher in the better-educated groups (high vs. low: RR = 0.84; 95% CI = 0.35-1.99, intermediate vs. low: RR = 0.82; 95% CI = 0.41-1.63).

CONCLUSION

In our cohort, highly educated patients had a faster cognitive decline than less educated patients but similar mortality rates. Our findings support the cognitive reserve hypothesis.

Language and Dementia: Neuropsychological Aspects

This article reviews recent evidence for the relationship between extralinguistic cognitive and language abilities in dementia. A survey of data from investigations of three dementia syndromes (Alzheimer's disease, semantic dementia and progressive nonfluent aphasia) reveals that, more often than not, deterioration of conceptual organization appears associated with lexical impairments, whereas impairments in executive function are associated with sentence- and discourse-level deficits. These connections between extralinguistic functions and language ability also emerge from the literature on cognitive reserve and bilingualism that investigates factors that delay the onset and possibly the progression of neuropsychological manifestation of dementia.

Brain structure and function related to cognitive reserve variables in normal aging, mild cognitive impairment and Alzheimer's disease

Cognitive reserve (CR) is the brain's capacity to cope with cerebral damage to minimize clinical manifestations. The 'passive model' considers head or brain measures as anatomical substrates of CR, whereas the 'active model' emphasizes the use of brain networks effectively. Sixteen healthy subjects, 12 amnestic mild cognitive impairment (MCI) and 16 cases with mild Alzheimer's disease (AD) were included to investigate the relationships between proxies of CR and cerebral measures considered in the 'passive' and 'active' models. CR proxies were inferred premorbid IQ (WAIS Vocabulary test), 'education-occupation', a questionnaire of intellectual and social activities and a composite CR measure. MRI-derived whole-brain volumes and brain activity by functional MRI during a visual encoding task were obtained. Among healthy elders, higher CR was related to larger brains and reduced activity during cognitive processing, suggesting more effective use of cerebral networks. In contrast, higher CR was associated with reduced brain volumes in MCI and AD and increased brain function in the latter, indicating more advanced neuropathology but that active compensatory mechanisms are still at work in higher CR patients. The right superior temporal gyrus (BA 22) and the left superior parietal lobe (BA 7) showed greatest significant differences in direction of slope with CR and activation between controls and AD cases. Finally, a regression analysis revealed that fMRI patterns were more closely related to CR proxies than brain volumes. Overall, inverse relationships for healthy and pathological aging groups emerged between brain structure and function and CR variables.

Intelligence quotient-adjusted memory impairment is associated with abnormal single photon emission computed tomography perfusion

Cognitive reserve among highly intelligent older individuals makes detection of early Alzheimer's disease (AD) difficult. We tested the hypothesis that mild memory impairment determined by IQ-adjusted norms is associated with single photon emission computed tomography (SPECT) perfusion abnormality at baseline and predictive of future decline. Twenty-three subjects with a Clinical Dementia Rating (CDR) score of 0, were reclassified after scores were adjusted for IQ into two groups, 10 as having mild memory impairments for ability (IQ-MI) and 13 as memory-normal (IQ-MN). Subjects underwent cognitive and functional assessments at baseline and annual follow-up for 3 years. Perfusion SPECT was acquired at baseline. At follow-up, the IQ-MI subjects demonstrated decline in memory, visuospatial processing, and phonemic fluency, and 6 of 10 had progressed to a CDR of 0.5, while the IQ-MN subjects did not show decline. The IQ-MI group had significantly lower perfusion than the IQ-MN group in parietal/precuneus, temporal, and opercular frontal regions. In contrast, higher perfusion was observed in IQ-MI compared with IQ-MN in the left medial frontal and rostral anterior cingulate regions. IQ-adjusted memory impairment in individuals with high cognitive reserve is associated with baseline SPECT abnormality in a pattern consistent with prodromal AD and predicts subsequent cognitive and functional decline.

Prevalence estimates and health-related correlates of cognitive impairment from a probability sample of community-residing Latino elders

OBJECTIVE

Prevalence estimates of cognitive impairment are provided from a probability sample of Latino elders, mostly Puerto Ricans. A profile of those with cognitive impairment is provided. Predictors of cognitive impairment and the association between depressive symptomatology and cognitive impairment are examined.

METHOD

A prevalence survey was conducted among a community sample of 205 Latino elders in New York City, drawn from the Centers for Medicare and Medicaid Services Medicare beneficiary tape files.

RESULTS

The prevalence ratio for cognitive impairment using scale-cut scores was 12%; the latent class estimate was .15 (SE = .025; 95% CI = .10 - .21). Individuals with cognitive impairment were older; had lower levels of education, income, and acculturation; and reported higher levels of diabetes, cardiovascular disease, and depressive symptomatology.

DISCUSSION

This study resulted in the identification of a cluster of socioeconomic, health, and mental health factors that may influence the functional ability of older Puerto Ricans.

Cognitive stimulation intervention for elders with mild cognitive impairment compared with normal aged subjects: preliminary results

BACKGROUND AND AIMS

Cognitive training programs have been developed for Alzheimer's disease patients and the healthy elderly population. Collective cognitive stimulation programs have been shown to be efficient for subjects with memory complaint. The aim of this study was to evaluate the benefit of such cognitive programs in populations with Mild Cognitive Impairment (MCI).

METHODS

Twelve patients with MCI and twelve cognitively normal elders were administered a cognitive stimulation program. Cognitive performance (Logical Memory, Word paired associative learning task, Trail Making Test, verbal fluency test) were collected before and after the intervention. A gain score [(post-score - pre-score)/ pre-score] was calculated for each variable and compared between groups.

RESULTS

The analysis revealed a larger intervention size effect in MCI than in normal elders' performances on the associative learning task (immediate recall: p<0.05, delayed recall: p<0.01). The intervention was more beneficial in improving associative memory abilities in MCI than in normal subjects. At the end of the intervention, the MCI group had lower results than the normal group only for the delayed recall of Logical Memory.

CONCLUSIONS

Although further studies are needed for more details on the impact of cognitive stimulation programs on MCI patients, this intervention is effective in compensating associative memory difficulties of these patients. Among non-pharmacological interventions, cognitive stimulation therapy is a repeatable and inexpensive collective method that can easily be provided to various populations with the aim of slowing down the rate of decline in elderly persons with cognitive impairment.

Cognitive sequelae in acute respiratory distress syndrome patients with and without recall of the intensive care unit

Some critically ill patients have dramatic recollections of the intensive care unit (ICU), whereas 23-50% have little or no recollection of their ICU stay. In addition, cognitive impairments are common following critical illness and ICU treatment. Little is known regarding the relationship between cognitive sequelae and ICU recall. We assessed recall of the ICU and its relationship to cognitive functioning at hospital discharge and 1 and 2 years after discharge in 70 consecutive acute respiratory distress syndrome (ARDS) patients. Seventeen patients (24%) had no recall of the ICU. Patients without ICU recall had increased rates of cognitive sequelae at hospital discharge and 1-year follow-up compared with the ICU recall group. Patients without ICU recall had a greater magnitude of cognitive impairments at hospital discharge, but not at 1- or 2-year follow-up. Profile analysis showed significant group differences in general intellectual functioning, executive function, processing speed, and spatial skills at hospital discharge, but not at 1- or 2-year follow-up. Estimated premorbid intelligence scores were inversely related to the magnitude of cognitive sequelae, suggesting greater "cognitive reserve" in patients with fewer cognitive decrements.

Job demands and dementia risk among male twin pairs

BACKGROUND

Job characteristics may influence dementia risk, but some types of job complexity remain to be examined. Twin studies provide a useful methodology to examine job differences between pairs who share many environmental and genetic influences.

METHODS

Members of the NAS-NRC Twins Registry of World War II Veterans received a clinical evaluation for dementia and had job ratings from the Dictionary of Occupational Titles.

RESULTS

Cotwin-control models (n = 220 pairs) indicated lower dementia risk with greater job demands of reasoning, mathematics, language, and vocational training, with comparable results in case-control models (n=425 cases). These effects were significant among twin pairs discordant for 6 or more years, but not among those discordant between 3-5 years. Results were similar for Alzheimer's disease, and main effects were not further explained by zygosity or apolipoprotein E genotype.

CONCLUSIONS

Jobs that utilize data, academic skills, and extensive vocational training may protect against dementia; however, in twin pairs these effects only emerged among individuals who remained free of dementia several years after onset in their sibling.

Educational level as a modulator of cognitive performance and neuropsychyatric features in Parkinson disease

OBJECTIVES

To test a possible association between the educational level (EL), cognitive performance, and neuropsychiatric features in Parkinson disease (PD).

BACKGROUND

An inverse association has been reported between EL and cognitive dysfunction in patients with senile dementia of Alzheimer type but it is yet unsettled whether education has a similar effect on cognition in PD.

METHODS

Seventy-two PD patients (45 males, mean age 68.7+/-11.6 y) underwent a detailed neurologic examination, a battery of neuropsychologic tests, and questionnaires for the evaluation of psychosis, sleep disturbances, and depression. According to the number of educational years, patients were divided into 3 groups: low EL (0 to 8 y), (15 patients), intermediate EL (9 to 12 y) (28 patients), and high EL (>/=13 y) (29 patients).

RESULTS

Patients with a higher EL had a better cognitive function and an association was found between the patients' EL and their scores in various neuropsychologic tests mainly those sensitive to frontal lobe dysfunction. Low education was associated with an increased risk for hallucinations and a trend for more depression, delusions, and sleep disturbances.

CONCLUSIONS

The association between high educational attainment and the lower risk of cognitive dysfunction suggest that education might modulate cognitive performance in PD.

Use it or lose it? SES mitigates age-related decline in a recency/recognition task

An important goal of aging research is to determine factors leading to individual differences that might compensate for some of the deleterious effects of aging on cognition. To determine whether socio-economic status (SES) plays a role in mitigating age-related decrements in the recollection of contextual details, we categorized older participants into low- and high-SES groups. Event-related potentials (ERPs) and behavioral data were recorded in a picture memory task involving recency and recognition judgments. Young, old-low and old-high SES groups did not differ in recognition performance. However, on recency judgments, old-low subjects performed at chance, whereas old-high subjects did not differ significantly from young adults. Consistent with their preserved recency performance, a long-duration frontal negativity was significantly larger for recency compared to recognition trials in the ERPs of the old-high SES group only. These data suggest that older adults with higher SES levels can use strategies to compensate for the adverse effects of aging in complex source memory tasks by recruiting additional neural resources apparently not required by the young.

Global cerebral blood flow in relation to cognitive performance and reserve in subjects with mild memory deficits

PURPOSE

This study was undertaken to explore the mechanisms underlying cognitive reserve in subjects with mild memory deficits by using positron emission tomography (PET).

METHODS

Global cerebral blood flow (gCBF) and cerebrovascular reserve (CVR) measurements were performed in 15 elders (5 men, 10 women, 62-84, 71.8 +/- 6.2 years) meeting criteria for mild cognitive impairment (MCI). PET consisted of quantitative [(15)O]water determinations of CBF, two at baseline and one postadministration of acetazolamide (ACZ).

RESULTS

Mean gCBF were 44.9 +/- 5.5 during counting, 44.5 +/- 6.7 for the memory task, and 60.2 +/- 4.8 ml/min/100 g for post-ACZ (CVR of 33.9 +/- 13.2%). Task-related gCBF change was significantly related to memory score, performance on the Trail Making Test B (Trails-B), premorbid IQ, and education, and differed significantly between the learning-based groups.

CONCLUSIONS

Cognitive reserve appears analogous to cardiac reserve. The ability to alter gCBF paralleled performance on general cognitive measures, was enhanced in higher levels of cognitive reserve, and was impaired in individuals who no longer appear to benefit from repeated exposure to testing.

Influence of premorbid IQ and education on progression of Alzheimer's disease

BACKGROUND

Lower education is associated with a higher risk of developing Alzheimer's disease (AD). Years of education and measures of general intellectual function (IQ) are highly correlated. It is important to determine whether there is a relationship between education and AD outcomes that is independent of IQ.

OBJECTIVE

To test the hypothesis that premorbid IQ is a stronger predictor of cognitive decline, global progression, and overall survival, than education in patients with AD.

METHODS

The study included 478 probable AD patients (322 women and 156 men, mean age 74.5 years) followed in a large AD referral center for a mean of 3.2 years. Eligible participants had a baseline estimate of premorbid IQ using the American version of the Nelson Adult Reading Test (AMNART) and at least one follow-up visit with complete neuropsychological assessment. We used random effects linear regression analysis, and Cox proportional hazards analysis to determine whether or not education and/or premorbid IQ were independently associated with cognitive decline, global progression of AD, and survival.

RESULTS

When the baseline AMNART score was included in regression models along with education and other demographic variables, AMNART score, but not education, was associated with a higher baseline score and slower rate of decline in MMSE and ADAS-Cog scores, and the Clinical Dementia Rating sum of boxes score. Neither higher premorbid IQ nor higher education was associated with longer survival.

CONCLUSIONS

We conclude that a baseline AMNART score is a better predictor of cognitive change in AD than education, but neither variable is associated with survival after diagnosis.

Attention and psychomotor speed decline in patients with temporal lobe epilepsy: A longitudinal study

PURPOSE

To assess the possible cognitive alterations in epilepsy patients compared with controls over 5 years, and to investigate the clinical variables mainly implied in mental impairment.

METHODS

In our longitudinal single-center study, 50 patients with temporal lobe epilepsy (TLE) and 50 controls were administered the same battery of comprehensive neuropsychological tests at baseline and after 5 years.

RESULTS

TLE patients showed a significant impairment in attention and psychomotor speed compared with controls after 5 years, while the other cognitive domains did not exhibit any important changes. This worsening was mainly related to the duration of epilepsy, the age at onset, a history of tonic-clonic seizures and a low educational level.

CONCLUSIONS

We believe that tapping the attention and psychomotor speed decline in TLE patients should be considered relevant for future research, in order to achieve a deeper understanding of the cognitive dimensions of this field.

Cognitive reserve and Alzheimer disease

Epidemiologic evidence suggests that individuals with higher IQ, education, occupational attainment, or participation in leisure activities have a reduced risk of developing Alzheimer disease (AD). The concept of cognitive reserve (CR) posits that individual differences in how tasks are processed provide differential reserve against brain pathology or age-related changes. This may take 2 forms. In neural reserve, preexisting brain networks that are more efficient or have greater capacity may be less susceptible to disruption. In neural compensation, alternate networks may compensate for pathology's disruption of preexisting networks. Imaging studies have begun to identify the neural substrate of CR. Because CR may modulate the clinical expression of AD pathology, it is an important consideration in studies of "preclinical" AD and treatment studies. There is also the possibility that directly enhancing CR may help forestall the diagnosis of AD.

Mild cognitive impairment and the 7 uses of epidemiology

In 1907, Alzheimer's single case report of presenile dementia led to the condition being recognized as a rare disease of middle-aged people. In 1964, Roth and colleagues reported an epidemiologic survey showing that the same condition was in fact a relatively common disease of the elderly. In 1987, Katzman introduced the concept of brain reserve, suggesting how individuals could have Alzheimer disease pathology in their brains without clinically manifesting the disease. In 1999, Petersen described mild cognitive impairment (MCI) as an amnestic state, since broadened to include other cognitive deficits, which, in the majority of patients, was a prelude to the development of full-blown Alzheimer disease or other dementia. MCI today is in some ways analogous to Alzheimer disease a century ago. We recognize and describe MCI clinically, among patients with memory complaints, but we do not know its distribution, outcomes, and risk factors in the elderly population at large. All population-based studies to date have found MCI to be an unstable and heterogeneous entity with a far wider range of outcomes than in the clinical setting, including reversion to normal in a substantial proportion. However, these studies thus far have been purely descriptive, and retro-fitted on to existing studies of dementia, using measurements not necessarily appropriate for the assessment of MCI. This review will address what is known and what has yet to be determined about MCI from the perspectives of the classic 7 uses of epidemiology.

The relation of lifetime cognitive activity and lifetime access to resources to late-life cognitive function in older African Americans

Research in older Caucasians has demonstrated that cognitive activity is related to cognitive function in late adulthood. Knowledge of this association is limited in older minority populations. We examined the relation of cognitive activity and access to cognitive resources, with cognitive function in a group of 108 older African Americans. We constructed two scales to measure the frequency of cognitive activity and the presence of resources that promote cognitive activity during early and late life. Both measures had high internal consistency and the cognitive activity scale had adequate temporal stability over a 4-week interval. In analyses that controlled for age and education, more frequent lifetime cognitive activity was related to current cognitive function, but lifetime cognitive resources only approached significance. The results suggest that both measures are psychometrically sound in a minority population and that lifetime cognitive activity may contribute to current cognitive function in African Americans.

Early-life risk factors for Alzheimer disease

Research findings obtained over the past 20 years suggest that Alzheimer disease (AD) may have its origins in early life. In this review, we consider the evidence for early-life risk factors for this illness. We propose that risk factors that predict neuropathology are largely distinct from those related to the clinical expression of Alzheimer disease. Early-life risk factors for pathology include genes, chromosomal abnormalities, head injury, insulin resistance, and inflammation. With regard to risk factors for clinical expression of Alzheimer disease, six general groups of childhood exposures are reviewed: (1) perinatal conditions, (2) early-life brain development, (3) early-life body growth, (4) early-life socioeconomic conditions, (5) environmental enrichment, and (6) cognitive reserve. The literature reviewed suggests that risk of Alzheimer disease is probably not determined in any single time period but results from the complex interplay between genetic and environmental exposures throughout the life course. Enhancement or preservation of brain or cognitive reserve could delay the onset of Alzheimer disease and in some cases prevent the disease from occurring altogether.

Comparative analysis of cognitive impairment among Mexicans and Spanish-speaking immigrant's elders

OBJECTIVE

This study aims to compare the prevalence of cognitive impairment among older Mexicans and Spanish-speaking U.S. immigrants.

METHODS

The relationship of cognitive impairment with social and demographic variables was explored using data from five different population based survey studies.

RESULTS

Prevalence rates increased with age, with low educational level, didn't show a clear association with gender and decreased in married subjects. Estimates of cognitive and functional impairment combined are greater in the immigrant samples than those for Mexican residents. Primary memory measures are the least discriminative for cognitive impairment, whereas orientation, attention, and secondary verbal memory measures discriminate better.

DISCUSSION

Mexicans and Spanish-speaking USA immigrants have similar prevalence estimates of cognitive impairment. However, prevalence of functional impairment differs between Mexicans and immigrants because of measurement issues and cultural factors.

Cognitive Reserve and Alzheimer Disease

Epidemiologic evidence suggests that individuals with higher IQ, education, occupational attainment, or participation in leisure activities have a reduced risk of developing Alzheimer disease (AD). The concept of cognitive reserve (CR) posits that individual differences in how tasks are processed provide differential reserve against brain pathology or age-related changes. This may take 2 forms. In neural reserve, preexisting brain networks that are more efficient or have greater capacity may be less susceptible to disruption. In neural compensation, alternate networks may compensate for pathology's disruption of preexisting networks. Imaging studies have begun to identify the neural substrate of CR. Because CR may modulate the clinical expression of AD pathology, it is an important consideration in studies of "preclinical" AD and treatment studies. There is also the possibility that directly enhancing CR may help forestall the diagnosis of AD.

Education and rates of cognitive decline in incident Alzheimer's disease

BACKGROUND

Some (but not all) epidemiological studies have noted faster rates of progression in high education patients with Alzheimer's disease (AD), which has been attributed to harbouring/tolerating a higher pathological burden at the time of clinical dementia for subjects with higher education. We wanted to assess the relationship between education and rates of decline in AD.

METHODS

During the course of a community based multiethnic prospective cohort study of individuals aged > or = 65 years living in New York, 312 patients were diagnosed with incident AD and were followed overall for 5.6 (up to 13.3) years. The subjects received an average of 3.7 (up to 9) neuropsychological assessments consisting of 12 individual tests. With the aid of a normative sample, a standardised composite cognitive score as well as individual cognitive domain scores were calculated. Generalised estimating equation models were used to examine the association between education and rates of cognitive decline.

RESULTS

Composite cognitive performance declined by 9% of a standard deviation per year. Rates of decline before and after AD incidence were similar. For each additional year of education there was 0.3% standard deviation lower composite cognitive performance for each year of follow up. The association between higher education and faster decline was noted primarily in the executive speed (0.6%) and memory (0.5%) cognitive domains and was present over and above age, gender, ethnicity, differential baseline cognitive performance, depression, and vascular comorbidity.

CONCLUSIONS

We conclude that higher education AD patients experience faster cognitive decline.

Leisure activities and the risk of amnestic mild cognitive impairment in the elderly

OBJECTIVE

To study the influence of leisure activity participation on risk of development of amnestic mild cognitive impairment (aMCI).

METHODS

The authors examined the relationship between baseline level of participation in leisure activities and risk of aMCI in a prospective cohort of 437 community-residing subjects older than 75 years, initially free of dementia or aMCI, using Cox analysis adjusted for age, sex, education, and chronic illnesses. The authors derived Cognitive and Physical Activity Scales based on frequency of participation in individual activities.

RESULTS

Over a median follow-up of 5.6 years, 58 subjects had development of aMCI. A one-point increase on the Cognitive (hazard ratio [HR] 0.95, 95% CI 0.91 to 0.99) but not Physical Activities Scale (HR 0.97, 95% CI 0.93 to 1.01) was associated with lower risk of aMCI. Subjects with Cognitive Activity scores in the highest (HR 0.46, 95% CI 0.24 to 0.91) and middle thirds (HR 0.52, 95% CI 0.29 to 0.96) had a lower risk of aMCI compared with subjects in the lowest third. The association persisted even after excluding subjects who converted to dementia within 2 years of meeting criteria for aMCI.

CONCLUSIONS

Cognitive activity participation is associated with lower risk of development of amnestic mild cognitive impairment, even after excluding individuals at early stages of dementia.

The effect of education and occupational complexity on rate of cognitive decline in Alzheimer's patients

We explored the effect of education and occupational complexity on the rate of cognitive decline (as measured by the Mini-Mental State Examination) in 171 patients with a confirmed Alzheimer's disease (AD) diagnosis. Complexity was measured as substantive complexity of work and complexity of work with data, people, and things. Average lifetime occupational complexity was calculated based on years at each occupation. Participants were followed for an average of 2.5 years and 3.7 visits. In multivariate mixed-effects models, high education, high substantive complexity, and high complexity of work with data and people predicted faster rates of cognitive decline, controlling for age, gender, native language, dementia severity, and entry into the analyses at initial versus follow-up testing. These results provide support for the concept of cognitive reserve according to which greater reserve may postpone clinical onset of AD but also accelerate cognitive decline after the onset.

Hallucinations, cognitive decline, and death in Alzheimer's disease

The relation of psychotic symptoms to cognitive decline and mortality in Alzheimer's disease (AD) was examined during a mean of 2.2 years in 478 persons selected from clinical settings. Psychotic symptoms were ascertained at baseline and cognition was assessed semiannually with nine tests from which a global measure was formed. In analyses that controlled for age, sex, race, and education, hallucinations (29.6%), especially visual ones, were associated with more rapid global cognitive decline and increased mortality, even after controlling for baseline level of cognition and use of antipsychotic medication, and the association with mortality increased with higher level of education. Delusions and misperceptions were not strongly related to cognitive decline or mortality. The results suggest that hallucinations in Alzheimer's disease, particularly visual ones, are associated with more rapid progression.

Stigmatization in Alzheimer's disease research on African American elders

Stigmatization in research sustains the spread of the silent epidemic of Alzheimer's disease (AD) in African American populations. Researchers use stereotypes and inappropriate assumptions to select a paradigm to examine the symptoms of AD. This paradigm fails to encompass the symptoms as manifested by African American elders. Yet, stigmatization can be minimized by recognizing the genetic heterogeneity of the symptoms within the general population, especially those manifested by African American elders. Thus, researchers can utilize pioneering genetic analyses to identify other paradigms critical in the assessment and proactive treatment of the symptoms of AD needed for this vulnerable population.

Cognitive decline and literacy among ethnically diverse elders

Researchers on genetic and environmental influences on risk for Alzheimer's disease must be prepared for the growing ethnic and racial diversity of our participants. Within the investigation, years of education has typically served as a proxy for cognitive reserve, which may be one factor in influencing risk of cognitive decline among aging people. However, among ethnic minorities, years of education is a poor reflection of the value of educational experience and native ability. This study was conducted among 1002 ethnically diverse English-speaking residents of Northern Manhattan who were cognitively and functionally normal at a baseline evaluation. We found that literacy level was a better predictor of decline in memory, executive function, and language skills than was years of education. The results of this study suggest that in an ethnically diverse cohort, literacy level should be considered as a mediator of the interactions of biological and environmental factors on cognitive decline.

Cognitive reserve: a SPECT study of 132 Alzheimer's disease patients with an education range of 0-19 years

This study examines the associations between education, cerebral perfusion, and cognitive test performance among 132 patients with Alzheimer's disease. The participants had had between 0 and 19 years of formal schooling, and had either mild or moderate dementia according to the Clinical Dementia Rating Scale. Cerebral perfusion was evaluated by the (99m)Tc-hexamethylpropylene amine oxime single photon emission computed tomography. The Mini-Mental State Examination and the Cognitive Abilities Screening Instrument were used to assess cognitive performance. For patients at each clinical dementia severity level, statistical parametric mapping was used to examine voxel by voxel the association between education and cerebral perfusion, and Pearson's correlation coefficients were calculated between education and cognitive test scores. Years of formal schooling had negative associations with cerebral perfusion and positive associations with cognitive test scores. The brain regions showing a significant education effect on perfusion involved bilateral posterior association areas in mild dementia, and bilateral parieto-temporo-frontal areas in moderate dementia. The present findings indicate that the cognitive reserve effect starts at the low end of the education range. They also suggest that the main effect of more education is a more facile use of alternative brain circuits instead of locally increased synaptic connections.

Detecting effects of donepezil on visual selective attention using signal detection parameters in Alzheimer's disease

BACKGROUND

Attentional function is impaired in Alzheimer's disease (AD). Moreover, attention is mediated by acetylcholine. But, despite the widespread use of acetylcholinesterase inhibitors (AChE-I) to augment available acetylcholine in AD, measures of attentional function have not been used to assess the drug response.

OBJECTIVES

We hypothesized that as cholinergic augmentation impacts directly on the attentional system, higher-order measures of visual selective attention would be sensitive to effects of treatment using an AChE-I (donepezil hydrochloride). We also sought to determine whether these attentional measures were more sensitive to treatment than other measures of cognitive function.

METHODS

Seventeen patients with AD (8 untreated, 9 treated with donepezil) were contrasted on performance of a selective cancellation task. Two signal detection parameters were used as outcome measures: decision strategy (beta, beta) and discriminability (d-prime, d'). Standard screening and cognitive domain measures of vigilance, language, memory, and executive function were also contrasted.

RESULTS

Treated patients judged stimuli more conservatively (p = 0.29) by correctly endorsing targets and rejecting false alarms. They also discriminated targets from distractors more easily (p = 0.58). The screening and neuropsychological measures failed to differentiate the groups.

CONCLUSIONS

Higher-order attentional measures captured the effects of donepezil treatment in small groups of patients with AD. The results suggest that cholinergic availability may directly affect the attentional system, and that these selective attention measures are sensitive markers to detect treatment response.

Education modifies the effect of apolipoprotein epsilon 4 on cognitive decline

OBJECTIVES

To assess the influence of education on the association between apolipoprotein E and cognitive change.

DESIGN

Prospective cohort.

PARTICIPANTS

HMO-based sample of 2168 non-demented community-dwelling elderly followed over 6 years.

MEASUREMENTS

Generalized estimating equations were used with the difference between baseline and follow-up cognitive abilities screening instrument (CASI) as the outcome variable.

RESULTS

At follow-up, 6% of the sample had a decline of 1.5 S.D. or greater on the CASI. Compared to individuals without an APOE4 allele, individuals with a single APOE4 allele did not have greater CASI decline. By contrast, individuals with two APOE4 alleles experienced greater decline in cognitive performance and the magnitude of that decline decreased as years of educational attainment increased. These relationships held after adjusting for age, gender, ethnicity, depression, diabetes, and history of vascular disease.

CONCLUSION

Lower education was associated with steep 4-year cognitive decline for APOE4 homozygotes but not for APOE4 heterozygotes. Potentially modifiable host factors such as education could influence the association of high-risk genotypes and cognitive decline.

Is Cognitive Reserve Applicable to Epilepsy? The Effect of Educational Level on the Cognitive Decline After Onset of Epilepsy

PURPOSE

The aim of this study was to know the effect of education level (EL) on the cognitive change after onset of epilepsy. The rationale is that people with high EL may have more cognitive reserve and show resistance to damage brought about by epilepsy.

METHODS

Patients were from an outpatient epilepsy clinic of a national university hospital. All received initial and repeated neuropsychological tests and the Cognitive Ability Screening Instrument (CASI), at an interval of 12 months. CASI consists of nine items, with a total score of 100. We compared the differences between the two tests, in terms of z-scores. The EL was divided into high and low with a cut-off at 12 years, and age at entry was divided with a cut-off at 38 years. Epilepsy severity was divided into intractable and nonintractable.

RESULTS

A total of 64 patients completed the study, including 31 with high EL and 33 with low EL, with no differences in gender and epilepsy severity between groups. In general, patients had cognitive impairment in multiple domains. At the baseline, the effect of EL was found for all items except remote memory and orientation, whereas the effect of age was observed for remote and recent memory. At the 12-month follow-up, subjects with high EL showed deterioration in mental manipulation, whereas subjects with low EL showed improvement in verbal fluency but deterioration in attention.

CONCLUSIONS

Patients with high EL have better cognitive functioning than those with low EL after epilepsy has developed, which supports the cognitive reserve theory. However, 1-year follow-up might be too short to see significant changes between groups.

The Relation Between Brain Activity During Memory Tasks and Years of Education in Young and Older Adults

Higher education is associated with less age-related decline in cognitive function, but the mechanism of this protective effect is unknown. The authors examined the effect of age on the relation between education and brain activity by correlating years of education with activity measured using functional MRI during memory tasks in young and older adults. In young adults, education was negatively correlated with frontal activity, whereas in older adults, education was positively correlated with frontal activity. Medial temporal activity was associated with more education in young adults but less education in older adults. This suggests that the frontal cortex is engaged by older adults, particularly by the highly educated, as an alternative network that may be engaged to aid cognitive function.

Cognitive reserve and the neurobiology of cognitive aging

A hypothetical construct of "cognitive reserve" is widely used to explain how, in the face of neurodegenerative changes that are similar in nature and extent, individuals vary considerably in the severity of cognitive aging and clinical dementia. Intelligence, education and occupational level are believed to be major active components of cognitive reserve. Here, we summarize the main features of cognitive aging and their neuropathological correlates. We describe the neurobiology of cognitive aging and conclude that perturbations of neural health attributable to oxidative stress and inflammatory processes alone are insufficient to distinguish cognitive aging from Alzheimer's disease. We introduce the concept of cognitive reserve and illustrate its utility in explaining individual differences in cognitive aging. Structural and functional brain imaging studies suggest plausible neural substrates of cognitive reserve, probably involving processes that support neuroplasticity in the aging brain. The cognitive reserve hypothesis conforms with reported associations between early and mid life lifestyle choices, early education, lifelong dietary habit, leisure pursuits and the retention of late life mental ability.

Frequency and risk factors of vascular cognitive impairment three months after ischemic stroke in china: the Chongqing stroke study

BACKGROUND

Frequency of poststroke cognitive impairment is high in western countries, and the risk factors of poststroke cognitive impairment have not been fully understood yet. We sought to examine the frequency and risk factors of cognitive impairment after ischemic stroke in a large stroke cohort of China.

METHODS

A total of 434 consecutive patients with ischemic stroke were enrolled. The cognitive status before and 3 months after stroke was evaluated using the Informant Questionnaire on Cognitive Decline in the Elderly and the Mini-Mental State Examination, respectively. Poststroke cognitive impairment was defined as cognitive impairment with concomitant stroke, stroke-related cognitive impairment was defined as cognitive impairment developing after index stroke, and cognitive impairment after first-ever stroke was defined as cognitive impairment developing after first-ever stroke. Logistic regression analysis was used to find the risk factors of cognitive impairment after stroke.

RESULTS

(1) Frequency of poststroke cognitive impairment was 37.1%, that of stroke-related cognitive impairment was 32.2%, and that of cognitive impairment after first-ever stroke was 29.6%. (2) The patients with cognitive impairment more often had older age, low educational level, atrial fibrillation, prior stroke, everyday drinking, left carotid territory infarction, multiple lesions, embolism, and dysphasia. (3) The factors associated with poststroke cognitive impairment in logistic regression analysis were age (OR 1.215, 95% CI 1.163-1.268), low educational level (OR 2.023, 95% CI 1.171-3.494), prior stroke (OR 5.130, 95% CI 2.875-9.157), everyday drinking (OR 2.013, 95% CI 1.123-3.607), dysphasia (OR 3.994, 95% CI 1.749-9.120), and left carotid territory infarction (OR 2.685, 95% CI 1.595-4.521).

CONCLUSIONS

Cognitive impairment is common 3 months after ischemic stroke in Chinese people. Risk factors for poststroke cognitive impairment include age, low educational level, everyday drinking, prior stroke, dysphasia, and left carotid territory infarction.

The contribution of the study of neurodegenerative disorders to the understanding of human memory

Memory impairment is one of the most common complaints affecting patients with neurodegenerative disorders, and its investigation has provided insights into the function and properties of human memory. The study of Alzheimer's disease has indicated the importance of mesial temporal structures and the hippocampus in episodic memory. In progressive supranuclear palsy, frontotemporal dementias, Parkinson's disease and Huntington's disease fronto-striatal networks are involved in working memory and higher level cognition. The study of semantic dementia, where there is lobar atrophy of the temporal lobe, has shown that the temporal neocortex has an important function in semantic memory. The investigation of human memory in neurodegenerative disorders suggests that the interaction of networks subserving episodic memory, semantic memory, and working memory contributes to higher level cognition and results in the fundamental homeostatic processes of recall and learning.

Use of IQ-adjusted norms to predict progressive cognitive decline in highly intelligent older individuals

Identifying high-functioning older individuals in preclinical phases of Alzheimer's disease (AD) may require more sensitive methods than the standard approach. The authors explored the utility of adjusting for premorbid intelligence to predict progressive cognitive decline or Mild Cognitive Impairment (MCI) in 42 highly intelligent older individuals. When scores were adjusted for baseline IQ, 9 participants had executive impairments, 11 had memory impairments, and 22 scored in the normal range. None were impaired according to standard age norms. Three and a half years later, 9 participants with IQ-adjusted memory impairment declined in naming, visuospatial functioning, and memory; 6 convened to MCI. Three participants with normal memory declined. Implications for using IQ-adjusted norms to predict preclinical AD are discussed.

Prophecies of childhood: how children's social environments and biological propensities affect the health of populations

During the past decade, important steps have been taken globally to improve the status of children. Concurrently, significant advances have been made toward understanding how child development is shaped by transactions between biological and environmental influences. Despite such advances, ongoing adversities in the lives of children worldwide undermine the development of individuals and thus the health of nations. The primary tenets of this paper are that: children continue to suffer a disproportionate share of the world's adversities; exposure to early adversities is not only associated with increased morbidity during childhood, but also across the lifespan; and recent advances in understanding the operation and ontogeny of stress-response systems can help explain how adversity is translated into lifelong effects on health. Acknowledging the long-lasting sequelae of childhood adversity has important implications for public health and society.

Baisse rapide du Mini Mental State Examination: étude REAL.FR

BACKGROUND

Alzheimer's disease is a chronic pathology requiring regular follow-up. The predictive factors of rapid cognitive decline remain unclear.

OBJECTIVES

To analyse the baselines characteristics of patients at increased risk of rapid cognitive decline.

METHODS

This study presents transversal data on a community-based sample of 340 patients diagnosed with probable Alzheimer's disease and followed by REAL.FR group. Rapid cognitive decline was defined as a 3-points or greater loss on the Mini Mental State Examination (MMSE) within six months.

RESULTS

54% of patients presented a rapid cognitive decline. Logistic regression analysis showed a positive association between rapid cognitive decline and a MMSE < or = 20 (p < 0.003) or a greater BMI (p < 0.02) and a tendency towards a negative correlation with anxiety (p = 0.06) and negative correlation with the burden severity (p < 0.05).

CONCLUSIONS

Patients with a worse cognitive status, a greater BMI and less anxiety or burden were at increased risk of rapid cognitive decline. Future studies should focus on determining etiologies for patients with rapid cognitive loss and help clinicians target these patients for interventions aiming to delay or stabilise the course of this disease.

Risk Factors for Alzheimer Disease: A Population-Based Case-Control Study in Istanbul, Turkey

The objective is to study risk factors for Alzheimer disease (AD) in Istanbul, Turkey. This is a population-based case-control study. We screened people over age 70 in the community for cognitive impairment. The screen positives and a proportion of screen negatives underwent neurologic examination in the second phase. Cases were 57 "probable" AD patients and controls were 127 cognitively normal individuals identified by neurologic examination. Odds ratios (OR) were calculated using multivariate logistic regression analysis. Having a university/college degree had a protective effect on AD risk (OR = 0.10, 95% confidence interval [CI] = 0.02-0.50). Exposure to occupational electromagnetic field had an OR of 4.02 (95% CI = 1.02-15.78). Use of electricity for residential heating also showed elevated risk (OR = 2.77, 95% CI = 1.12-6.85). Our results suggest that having a higher education is protective from AD and that electromagnetic field exposure at work or at home is a significant risk factor.

Leisure activities and the risk of dementia in the elderly

BACKGROUND

Participation in leisure activities has been associated with a lower risk of dementia. It is unclear whether increased participation in leisure activities lowers the risk of dementia or participation in leisure activities declines during the preclinical phase of dementia.

METHODS

We examined the relation between leisure activities and the risk of dementia in a prospective cohort of 469 subjects older than 75 years of age who resided in the community and did not have dementia at base line. We examined the frequency of participation in leisure activities at enrollment and derived cognitive-activity and physical-activity scales in which the units of measure were activity-days per week. Cox proportional-hazards analysis was used to evaluate the risk of dementia according to the base-line level of participation in leisure activities, with adjustment for age, sex, educational level, presence or absence of chronic medical illnesses, and base-line cognitive status.

RESULTS

Over a median follow-up period of 5.1 years, dementia developed in 124 subjects (Alzheimer's disease in 61 subjects, vascular dementia in 30, mixed dementia in 25, and other types of dementia in 8). Among leisure activities, reading, playing board games, playing musical instruments, and dancing were associated with a reduced risk of dementia. A one-point increment in the cognitive-activity score was significantly associated with a reduced risk of dementia (hazard ratio, 0.93 [95 percent confidence interval, 0.90 to 0.97]), but a one-point increment in the physical-activity score was not (hazard ratio, 1.00). The association with the cognitive-activity score persisted after the exclusion of the subjects with possible preclinical dementia at base line. Results were similar for Alzheimer's disease and vascular dementia. In linear mixed models, increased participation in cognitive activities at base line was associated with reduced rates of decline in memory.

CONCLUSIONS

Participation in leisure activities is associated with a reduced risk of dementia, even after adjustment for base-line cognitive status and after the exclusion of subjects with possible preclinical dementia. Controlled trials are needed to assess the protective effect of cognitive leisure activities on the risk of dementia.

Which factors influence cognitive decline in older adults suffering from dementing disorders?

BACKGROUND

Although extensive research has been done on dementing disorders in recent decades, their natural course and prognosis are not yet well understood. The aim of our study was to assess cognitive decline in a representative sample of demented elderly and to analyse the predictive value of a broad spectrum of sociodemographic, neurological and clinical variables.

METHODS

A random sample of elderly patients in primary care (n = 407) was drawn from a total of 3721 patients. The sample has been stratified according to the degree of cognitive impairment as assessed by their GPs. The patients were examined by means of a standardized research interview, including comprehensive cognitive testing (Hierarchic Dementia Scale) and the assessment of neurologic and physical impairments as well as of mental state (CAMDEX criteria). After a mean interval of 28 months, a follow-up study was conducted using essentially the same instruments.

RESULTS

At baseline, 117 of the 407 patients were identified as suffering from mild, moderate, or severe dementia. The two-year follow-up of those patients revealed high mortality rates (53/117). The surviving patients showed significant cognitive decline, although the rate varied considerably between individuals. The rate of progression was strongly related to the initial degree of severity, but also to the use of psychotropic medication, which was associated with a more rapid deterioration.

CONCLUSIONS

There are some prognostic indicators that can help to establish the prognosis for dementia patients. The best indicator for both--the rate of cognitive decline and the probability of survival--is the severity of dementia.

Influence of cognitive reserve on neuropsychological functioning in Parkinson's disease

BACKGROUND

In recent years, attention has been drawn to the association between a low level of education and dementia, an almost generalized finding in the majority of studies on the prevalence of dementia where the level of education of the population was highly diversified. The protective effect of education is not limited to Alzheimer's disease but is also seen in other types of dementia, Parkinson's disease (PD), and even in the cognitive deterioration linked to aging Objective: To evaluate neuropsychological performance in (PD) subjects and to evaluate the influence of cognitive reserve (RC) on their neuropsychological performance.

SUBJECTS

An extensive neuropsychological battery of tests was applied to a total of 79 subjects, 33 of whom were diagnosed with PD.

MEASURES

RC scores were based on a combination of years of education, a measure of occupational attainment, and an estimate of premorbid intelligence.

RESULTS

As regards the specific disturbances found in the clinical group subjects, a lower performance in memory, attention, visuospatial, visuoconstructive, and perceptive skills was seen. With respect to our second objective, our results showed that patients diagnosed with PD who had a high RC reached a higher neuropsychological level of performance than those subjects with a low reserve.

CONCLUSIONS

Early neuropsychological impairments in PD are most evident in individuals with lower RC. As has been found in other neurological disorders, individuals with greater RC may be less sensitive to the initial clinical effects of the underlying neuropathological process.