Education and dementia: a meta-analytic study

Cognitive screening tools for identification of dementia in illiterate and low-educated older adults, a systematic review and meta-analysis

BACKGROUND

The majority of older adults with dementia live in low- and middle-income countries (LMICs). Illiteracy and low educational background are common in older LMIC populations, particularly in rural areas, and cognitive screening tools developed for this setting must reflect this. This study aimed to review published validation studies of cognitive screening tools for dementia in low-literacy settings in order to determine the most appropriate tools for use.

METHOD

A systematic search of major databases was conducted according to PRISMA guidelines. Validation studies of brief cognitive screening tests including illiterate participants or those with elementary education were eligible. Studies were quality assessed using the QUADAS-2 tool. Good or fair quality studies were included in a bivariate random-effects meta-analysis and a hierarchical summary receiver operating characteristic (HSROC) curve constructed.

RESULTS

Forty-five eligible studies were quality assessed. A significant proportion utilized a case-control design, resulting in spectrum bias. The area under the ROC (AUROC) curve was 0.937 for community/low prevalence studies, 0.881 for clinic based/higher prevalence studies, and 0.869 for illiterate populations. For the Mini-Mental State Examination (MMSE) (and adaptations), the AUROC curve was 0.853.

CONCLUSION

Numerous tools for assessment of cognitive impairment in low-literacy settings have been developed, and tools developed for use in high-income countries have also been validated in low-literacy settings. Most tools have been inadequately validated, with only MMSE, cognitive abilities screening instrument (CASI), Eurotest, and Fototest having more than one published good or fair quality study in an illiterate or low-literate setting. At present no screening test can be recommended.

Does more education mean less disability in people with dementia? A large cross-sectional study in Taiwan

BACKGROUND

WHO Disability Assessment Schedule 2.0 (WHODAS 2.0) is a feasible tool for assessing functional disability and analysing the risk of institutionalisation among elderly patients with dementia. However, the data for the effect of education on disability status in patients with dementia is lacking. The aim of this large-scale, population-based study was to analyse the effect of education on the disability status of elderly Taiwanese patients with dementia by using WHODAS 2.0.

METHODS

From the Taiwan Data Bank of Persons with Disability, we enrolled 7698 disabled elderly (older than 65 years) patients diagnosed with dementia between July 2012 and January 2014. According to their education status, we categorised these patients with and without formal education (3849 patients each). We controlled for the demographic variables through propensity score matching. The standardised scores of these patients in the six domains of WHODAS 2.0 were evaluated by certified interviewers. Student's t-test was used for comparing the WHODAS 2.0 scores of patients with dementia in the two aforementioned groups. Poisson regression was applied for analysing the association among all the investigated variables.

RESULTS

Patients with formal education had low disability status in the domains of getting along and social participation than did patients without formal education. Poisson regression revealed that standardised scores in all domains of WHODAS 2.0-except self-care-were associated with education status.

CONCLUSIONS

This study revealed lower disability status in the WHODAS 2.0 domains of getting along and social participation for patients with dementia with formal education compared with those without formal education. For patients with disability and dementia without formal education, community intervention of social participation should be implemented to maintain better social interaction ability.

Leisure activities, education, and cognitive impairment in Chinese older adults: a population-based longitudinal study

BACKGROUND

We examine the association between leisure-time activities and the risk of developing cognitive impairment among Chinese older people, and further investigate whether the association varies by educational level.

METHODS

This follow-up study included 6,586 participants (aged 79.5 ± 9.8 years, range 65-105 years, 51.7% female) of the Chinese Longitudinal Healthy Longevity Survey who were aged ≥65 years and were free of cognitive impairment in 2002. Incident cognitive impairment was defined at the 2005 or 2008/2009 survey following an education-based cut-off on the adapted Chinese version of Mini-Mental State Examination (MMSE). Participation in cognitive activities (e.g. reading) and non-exercise physical activity (e.g. housework) was assessed by a self-reported scale. Cox proportional hazard models were employed to examine the association of leisure activities with incident cognitive impairment while controlling for age, gender, education, occupation, residence, physical exercise, smoking, drinking, cardiovascular diseases and risk factors, negative well-being, and physical functioning, and baseline MMSE score.

RESULTS

During a five-year follow-up, 1,448 participants developed incident cognitive impairment. Overall, a high level of participation in leisure activities was associated with a 41% decreased risk of cognitive impairment compared to low-level engagement in leisure activities after controlling for age, gender, education, and other confounders. Moreover, there was a significant interaction between leisure activity and educational level, such that the beneficial effect of leisure activities on cognitive function was larger in educated elderly than their uneducated counterparts, and only educated elderly benefited from cognitive activities.

CONCLUSIONS

Late-life leisure activities protect against cognitive impairment among elderly Chinese people, and the protective effects are more profound for educated elderly.

Estimating the prevalence of dementia using multiple linked administrative health records and capture-recapture methodology

Background

Obtaining population-level estimates of the incidence and prevalence of dementia is challenging due to under-diagnosis and under-reporting. We investigated the feasibility of using multiple linked datasets and capture–recapture techniques to estimate rates of dementia among women in Australia.

Methods

This work is based on the Australian Longitudinal Study on Women’s Health. A random sample of 12,432 women born in 1921–1926 was recruited in 1996. Over 16 years of follow-up records of dementia were obtained from five sources: three-yearly self-reported surveys; clinical assessments for aged care assistance; death certificates; pharmaceutical prescriptions filled; and, in three Australian States only, hospital in-patient records.

Results

A total of 2534 women had a record of dementia in at least one of the data sources. The aged care assessments included dementia records for 79.3% of these women, while pharmaceutical data included 34.6%, death certificates 31.0% and survey data 18.5%. In the States where hospital data were available this source included dementia records for 55.8% of the women. Using capture–recapture methods we estimated an additional 728 women with dementia had not been identified, increasing the 16 year prevalence for the cohort from 20.4 to 26.0% (95% confidence interval [CI] 25.2, 26.8%).

Conclusions

This study demonstrates that using routinely collected health data with record linkage and capture–recapture can produce plausible estimates for dementia prevalence and incidence at a population level.

Electronic supplementary material

The online version of this article (doi:10.1186/s12982-017-0057-3) contains supplementary material, which is available to authorized users.

Spies C, Pischon T. Cognitive Reserve and the Risk of Postoperative Cognitive Dysfunction

BACKGROUND

Post-operative cognitive dysfunction (POCD) occurs in 10 to 54% of older patients during the first few weeks after surgery, but little is known about risk factors predisposing to POCD.

METHODS

Systematic literature review and meta-analysis of cognitive reserve indicators and POCD risk.

RESULTS

Fifteen studies on 5104 patients were included. Follow-up periods spanned 1 day to 6 months. Educational level was the most commonly assessed cognitive reserve indicator, and a longer time spent in education was associated with a reduced risk of POCD (relative risk [RR] per year increment 0.90; 95% confidence interval: [0.87; 0.94]), i.e. each year increase in education was associated with a 10% reduced risk. Similar findings were made for some analyses on education as a categorical predictor (high school versus further/higher education, RR 1.71, [1.30; 2.25]; lower than high school versus further/higher education, RR 1.69, [1.17; 2.44]) though risk was equivalent for patients with high school education and those with lower than high school education (RR 1.02; [0.78; 1.32]).

CONCLUSION

Patients with a relatively higher level of education are at reduced risk of POCD. Risk stratification of surgical patients according to educational level may prove useful.

A Late Life Risk Index for Severe Cognitive Impairment in Mexico

BACKGROUND

Several dementia risk indices have been developed for older adults in high-income countries. However, no index has been developed for populations in low- or middle-income countries.

OBJECTIVE

To create a risk index for predicting severe cognitive impairment among adults aged ≥60 in Mexico and to compare the accuracy of this index to the Dementia Screening Indicator (DSI).

METHODS

This study included 3,002 participants from the Mexican Health and Aging Study (MHAS) interviewed in 2001 and 2012. The MHAS risk index included sociodemographic, health, and functional characteristics collected in 2001. A point value based on the beta coefficients from a multivariable logistic regression model was assigned to each risk factor and the total score was calculated.

RESULTS

The MHAS risk index (AUC = 0.74 95% CI = 0.70-0.77) and DSI (AUC = 0.72 95% CI = 0.69-0.77) had similar accuracy for discriminating between participants who developed severe cognitive impairment from those who did not. A score of ≥16 on the MHAS risk index had a sensitivity of 0.69 (95% CI = 0.64-0.70) and specificity of 0.67 (95% CI = 0.66-0.69). A score of ≥23 on the DSI had a sensitivity of 0.56 (95% CI = 0.50-0.63) and specificity of 0.78 (95% CI = 0.76-0.79).

DISCUSSION

The MHAS risk index and DSI have moderate accuracy for predicting severe cognitive impairment among older adults in Mexico. This provides evidence that existing dementia risk indices may be applicable in low- and middle-income countries such as Mexico. Future research should seek to identify additional risk factors that can improve the accuracy of the MHAS risk index.

From Brain Disease to Brain Health: Primary Prevention of Alzheimer's Disease and Related Disorders in a Health System Using an Electronic Medical Record-Based Approach

BACKGROUND

Alzheimer's disease and aging brain disorders are progressive, often fatal neurodegenerative diseases. Successful aging, modern lifestyles and behaviors have combined to result in an expected epidemic. Risks for these diseases include genetic, medical, and lifestyle factors; over 20 modifiable risks have been reported.

OBJECTIVES

We aim to primarily prevent Alzheimer's disease and related disorders through electronic medical record (EMR)-based screening, risk assessments, interventions, and surveillance.

DESIGN

We identified modifiable risks; developed human, systems and infrastructural resources; developed interventions; and targeted at-risk groups for the intervention.

SETTING

A Community Based Health System.

PARTICIPANTS

In year one (June 2015 to May 2016), 133 at-risk patients received brain health services with the goal of delaying or preventing Alzheimer's disease and related disorders.

MEASUREMENTS

We created mechanisms to identify patients at high risk of neurodegenerative disease; EMR-based structured clinical documentation support tools to evaluate risk factors and history; evidence-based interventions to modify risk; and the capacity for annual surveillance, pragmatic trials, and practice-based and genomic research using the EMR.

RESULTS

This paper describes our Center for Brain Health, our EMR tools, and our first year of healthy but at-risk patients.

CONCLUSION

We are translating research into primary prevention of Alzheimer's disease and related disorders in our health system and aim to shift the paradigm in Neurology from brain disease to brain health.

Education as protector against dementia, but what exactly do we mean by education?

OBJECTIVES

even though a great number of research studies have shown that high education has protective effects against dementia, some studies did not observe such a significant effect. In that respect, the aim of our study was to investigate and compare various operationalisation approaches of education and how they impact dementia risk within one sample.

METHODS

data were derived from the Leipzig longitudinal study of the aged (LEILA75+). Individuals aged 75 and older underwent six cognitive assessments at an interval of 1.5 years and a final follow-up 15 years after the baseline assessment. We operationalised education according to different approaches used in previous studies and analysed the impact on dementia incidence via multivariate cox regression modelling.

RESULTS

the results showed that whether education is identified as significant protector against dementia strongly depends on the operationalisation of education. Whereas the pure number of years of education showed statistically significant protective effects on dementia risk, other more complex categorical classification approaches did not. Moreover, completing >10 years of education or a tertiary level seems to be an important threshold to significantly reduce dementia risk.

CONCLUSION

findings suggest a protective effect of more years of education on a lower dementia risk with a particular critical threshold of completing >10 years of education. Further, the findings highlight that, when examining risks and protective factors of dementia, a careful consideration of the underlying definitions and operationalisation approaches is required.

Non-pharmacological strategies to delay cognitive decline

Non-pharmacological preventive strategies to delay cognitive decline have become the focus of recent research. This review aims to discuss evidence supporting the use of physical and cognitive activity to reduce the risk of cognitive decline and dementia in later life. Both strategies are associated with better cognitive health in older adults. This positive effect seems stronger for middle-aged and older adults with normal cognition and less clear when cognitive impairment is present. Physical and cognitive activities have been linked to indirect and direct biological factors affecting brain health. Future research will need to explore details about type, intensity, duration and combination of interventions. An important aim is standardization between studies, as well as evidence of improved clinical outcomes and cost-effectiveness. Identifying strategies that succeed at sustaining improved lifestyle is necessary, and the use of modern technology could play a crucial role in this regard. In the meantime advice on physical and cognitive activities should be included when health advice is given to middle-aged and older adults.

Higher Education Is Associated with a Lower Risk of Dementia after a Stroke or TIA. The Rotterdam Study

BACKGROUND

Higher education is associated with a lower risk of dementia, possibly because of a higher tolerance to subclinical neurodegenerative pathology. Whether higher education also protects against dementia after clinical stroke or transient ischemic attack (TIA) remains unknown.

METHODS

Within the population-based Rotterdam Study, 12,561 participants free of stroke, TIA and dementia were followed for occurrence of stroke, TIA and dementia. Across the levels of education, associations of incident stroke or TIA with subsequent development of dementia and differences in cognitive decline following stroke or TIA were investigated.

RESULTS

During 124,862 person-years, 1,463 persons suffered a stroke or TIA, 1,158 persons developed dementia, of whom 186 developed dementia after stroke or TIA. Risk of dementia after a stroke or TIA, compared to no stroke or TIA, was highest in the low education category (hazards ratio [HR] 1.46, 95% CI 1.18-1.81) followed by intermediate education category (HR 1.36, 95% CI 1.03-1.81). No significant association was observed in the high education category (HR 0.62, 95% CI 0.25-1.54). In gender stratified analyses, decrease in risk of dementia with increasing education was significant only in men.

CONCLUSION

Higher education is associated with a lower risk of dementia after stroke or TIA, particularly in men, which might be explained by a higher cognitive reserve.

Dementia in the USA: state variation in prevalence

BACKGROUND

The number of dementia patients will increase over the next decades. However, we lack information on the geographic distribution of these patients. We aimed to describe the variation of dementia prevalence and to then compare the observed to expected prevalence.

METHODS

This study is based on a 20% sample of Medicare beneficiaries in 2008. The crude dementia prevalence was calculated and age/sex standardized to the US population for states. We used the World Alzheimer Report 2009 prevalence to compare estimates.

RESULTS

4.8 million persons were included. The adjusted prevalence is 8.24%, varying from 5.96 to 9.55% across states. The diagnosed prevalence is lower than the expected in most states. Overall, we estimate over 100 000 undiagnosed dementia patients in Medicare.

CONCLUSIONS

The high state variation suggests that the number of diagnosed dementia cases does not fall evenly across all states and hence may require different levels of state-level planning.

Inverse relationship between cancer and Alzheimer's disease: a systemic review meta-analysis

Alzheimer's disease (AD) and cancer are both prevalent in the elderly. Some epidemiological researches have reported the negative association between AD and cancer, but the results are controversial. The present meta-analysis is aimed to clarify the association between cancer and AD. PubMed, Web of knowledge and the Cochrane library databases were searched for eligible publications. The analysis indicated that history of cancer was associated with a reduced risk of AD (ES 0.62, 95 % CIs 0.53-0.74; p < 0.001), with no significance between-study heterogeneity and publication bias. Similar results were found in subgroup analysis by stratifying variables with education and APOEε4 carriers, years of follow-up and sample size of cases. The negative association was also found in analysis of risk of cancer among patients with AD (ES 0.59, 95 % CIs 0.42-0.82; p = 0.002), but with evidence of between-study heterogeneity and publication bias. In order to identify sources of the heterogeneity, subgroup analysis was performed by stratifying variable with or without education adjusted, sample size of cases and years of follow-up. Negative association was found in all subgroup analysis except in studies with less than 5-year follow-up and with heterogeneity disappeared only in the subgroup analysis stratified with sample size of cases. Our results in the present meta-analysis support the negative association between AD and cancer. But further well-designed perspective studies with strict control of confounding factors are needed to clarify the association between AD and cancer.

Instrumental variable approaches to identifying the causal effect of educational attainment on dementia risk

PURPOSE

Education is an established correlate of cognitive status in older adulthood, but whether expanding educational opportunities would improve cognitive functioning remains unclear given limitations of prior studies for causal inference. Therefore, we conducted instrumental variable (IV) analyses of the association between education and dementia risk, using for the first time in this area, genetic variants as instruments as well as state-level school policies.

METHODS

IV analyses in the Health and Retirement Study cohort (1998-2010) used two sets of instruments: (1) a genetic risk score constructed from three single-nucleotide polymorphisms (SNPs; n = 7981); and (2) compulsory schooling laws (CSLs) and state school characteristics (term length, student teacher ratios, and expenditures; n = 10,955).

RESULTS

Using the genetic risk score as an IV, there was a 1.1% reduction in dementia risk per year of schooling (95% confidence interval, -2.4 to 0.02). Leveraging compulsory schooling laws and state school characteristics as IVs, there was a substantially larger protective effect (-9.5%; 95% confidence interval, -14.8 to -4.2). Analyses evaluating the plausibility of the IV assumptions indicated estimates derived from analyses relying on CSLs provide the best estimates of the causal effect of education.

CONCLUSIONS

IV analyses suggest education is protective against risk of dementia in older adulthood.

Implications of Risk Factors for Alzheimer's Disease in Canada's Indigenous Population

Background

Indigenous peoples in Canada have higher prevalence of modifiable risk factors for Alzheimer’s disease (AD). The relative importance of these risk factors on AD risk management is poorly understood.

Methods

Relative risks from literature and prevalence of risk factors from Statistics Canada or the First Nations Regional Health Survey were used to determine projected population attributable risk (PAR) associated with modifiable risk factors for AD (low education and vascular risk factors) among on- and off-reserve Indigenous and non-Indigenous people in Canada using the Levin formula.

Results

Physical inactivity had the highest PAR for AD among Indigenous and non-Indigenous peoples in Canada (32.5% [10.1%–51.1%] and 30.5% [9.2%–48.8%] respectively). The PAR for most modifiable risk factors was higher among Indigenous peoples in Canada, particularly among on-reserve groups. The greatest differences in PAR were for low educational attainment and smoking, which were approximately 10% higher among Indigenous peoples in Canada. The combined PAR for AD for all six modifiable risk factors was 79.6% among on-reserve Indigenous, 74.9% among off-reserve Indigenous, and 67.1% among non-Indigenous peoples in Canada. (All differences significant to p < .001.)

Conclusions

Modifiable risk factors are responsible for the most AD cases among Indigenous peoples in Canada. Further research is necessary to determine the prevalence of AD and the impact of risk factor modification among Indigenous peoples in Canada.

Income in midlife and dementia related mortality over three decades: A Norwegian prospective study

Studies on midlife income and dementia are scarce, and our main aim was to investigate midlife with later risk of dementia related mortality, adjusting for education and dementia related risk factors. The study population consisted of Norwegian men, aged 40–59 years in 1980 at income assessment, which participated in Norwegian health examination studies in the period 1980–2002 where risk factors such as cholesterol level, hypertension, smoking, cardiovascular disease, and diabetes were assessed. Dementia related mortality was defined as a dementia diagnosis on the death certificate until 2012. Cox regression was used. The study included 45,944 participants and 1062 dementia related deaths. There was no association between midlife income and dementia mortality risk (HR = 1.04, 95% confidence interval (CI) 0.85, 1.28 for the lowest fifth of income compared to those in the highest fifth). For total mortality, there was a strong inverse association with income (HR = 1.61, 95% CI 1.53, 1.69), which was attenuated when adjusting for education and risk factors, but still significant (HR = 1.27, 95% CI 1.20, 1.34). Lower educational attainment was significantly associated with increased dementia mortality risk, also after adjustment for income and other known risk factors (HR = 1.30, 95% CI 1.03, 1.64 comparing low versus high education). Midlife income was not associated with dementia related mortality, but low education was independently linked to increased risk of dementia related mortality. Our results support the cognitive reserve hypothesis suggesting that mental activity and not material resources are related to dementia related mortality.

Bridging the Translation Gap: From Dementia Risk Assessment to Advice on Risk Reduction

Dementia risk reduction is a global health and fiscal priority given the current lack of effective treatments and the projected increased number of dementia cases due to population ageing. There are often gaps among academic research, clinical practice, and public policy. We present information on the evidence for dementia risk reduction and evaluate the progress required to formulate this evidence into clinical practice guidelines. This narrative review provides capsule summaries of current evidence for 25 risk and protective factors associated with AD and dementia according to domains including biomarkers, demographic, lifestyle, medical, and environment. We identify the factors for which evidence is strong and thereby especially useful for risk assessment with the goal of personalising recommendations for risk reduction. We also note gaps in knowledge, and discuss how the field may progress towards clinical practice guidelines for dementia risk reduction.

The influence of smoking, sedentary lifestyle and obesity on cognitive impairment-free life expectancy

BACKGROUND

Smoking, sedentary lifestyle and obesity are risk factors for mortality and dementia. However, their impact on cognitive impairment-free life expectancy (CIFLE)has not previously been estimated.

METHODS

Data were drawn from the DYNOPTA dataset which was derived by harmonizing and pooling common measures from five longitudinal ageing studies. Participants for whom the Mini-Mental State Examination was available were included (N¼8111,48.6% men). Data on education, sex, body mass index, smoking and sedentary lifestyle were collected and mortality data were obtained from Government Records via data linkage.Total life expectancy (LE), CIFLE and years spent with cognitive impairment (CILE)were estimated for each risk factor and total burden of risk factors.

RESULTS

CILE was approximately 2 years for men and 3 years for women, regardless of age. For men and women respectively, reduced LE associated with smoking was 3.82and 5.88 years, associated with obesity was 0.62 and 1.72 years and associated with being sedentary was 2.50 and 2.89 years. Absence of each risk factor was associated with longer LE and CIFLE, but also longer CILE for smoking in women and being sedentary in both sexes. Compared with participants with no risk factors, those with 2þ had shorter CIFLE of up to 3.5 years depending on gender and education level.

CONCLUSIONS

Population level reductions in smoking, sedentary lifestyle and obesity increase longevity and number of years lived without cognitive impairment. Years lived with cognitive impairment may also increase.

Educational games for brain health: revealing their unexplored potential through a neurocognitive approach

Educational games link the motivational nature of games with learning of knowledge and skills. Here, we go beyond effects on these learning outcomes. We review two lines of evidence which indicate the currently unexplored potential of educational games to promote brain health: First, gaming with specific neurocognitive demands (e.g., executive control), and second, educational learning experiences (e.g., studying foreign languages) improve brain health markers. These markers include cognitive ability, brain function, and brain structure. As educational games allow the combination of specific neurocognitive demands with educational learning experiences, they seem to be optimally suited for promoting brain health. We propose a neurocognitive approach to reveal this unexplored potential of educational games in future research.

Polypathology and dementia after brain trauma: Does brain injury trigger distinct neurodegenerative diseases, or should they be classified together as traumatic encephalopathy?

Neuropathological studies of human traumatic brain injury (TBI) cases have described amyloid plaques acutely after a single severe TBI, and tau pathology after repeat mild TBI (mTBI). This has helped drive the hypothesis that a single moderate to severe TBI increases the risk of developing late-onset Alzheimer's disease (AD), while repeat mTBI increases the risk of developing chronic traumatic encephalopathy (CTE). In this review we critically assess this position-examining epidemiological and case control human studies, neuropathological evidence, and preclinical data. Epidemiological studies emphasize that TBI is associated with the increased risk of developing multiple types of dementia, not just AD-type dementia, and that TBI can also trigger other neurodegenerative conditions such as Parkinson's disease. Further, human post-mortem studies on both single TBI and repeat mTBI can show combinations of amyloid, tau, TDP-43, and Lewy body pathology indicating that the neuropathology of TBI is best described as a 'polypathology'. Preclinical studies confirm that multiple proteins associated with the development of neurodegenerative disease accumulate in the brain after TBI. The chronic sequelae of both single TBI and repeat mTBI share common neuropathological features and clinical symptoms of classically defined neurodegenerative disorders. However, while the spectrum of chronic cognitive and neurobehavioral disorders that occur following repeat mTBI is viewed as the symptoms of CTE, the spectrum of chronic cognitive and neurobehavioral symptoms that occur after a single TBI is considered to represent distinct neurodegenerative diseases such as AD. These data support the suggestion that the multiple manifestations of TBI-induced neurodegenerative disorders be classified together as traumatic encephalopathy or trauma-induced neurodegeneration, regardless of the nature or frequency of the precipitating TBI.

Fund of Information is More Strongly Associated with Neuropsychological Functioning Than Education in Older Spanish Adults

Educational influence on cognitive performance has been extensively agreed in Neuropsychology. Nonetheless, recent studies highlighted the need of better measurements to assess benefit from the schooling experience in order to further understand schooling influence on cognition. The WAIS-III Information subtest is proposed here to measure this influence at old age. Ninety-five older adults were divided according to their educational attainment and their Information subtest score, and completed extensive neuropsychological assessment. Performance on the Information subtest had a significant effect on all same cognitive functions as educational attainment, but also on additional domains. Moreover, cognitive performance on several tasks can be classified in three levels as a function of Information score. The WAIS-III Information subtest could be of special interest as a measurement of the benefit from educational experience not only to study cognition in Spanish older populations but also heterogeneous samples in terms of educational experiences and environments.

Exploring strategies to operationalize cognitive reserve: A systematic review of reviews

INTRODUCTION

The cognitive reserve hypothesis suggests that across the lifespan, higher education, regular participation in social or mentally stimulating activities, and complexity of occupation increase an individual's resistance to dementia. However, there is currently no consensus regarding how to assess or measure cognitive reserve.

METHOD

We performed a systematic review of reviews focused on the concept of cognitive reserve to examine key elements of the definition and highlight limitations. We searched Embase.com, MEDLINE (OvidSP), the Cochrane Library, Web of Science, Scopus, Google Scholar, and PubMed.

RESULTS

Five systematic reviews were identified. These incorporated findings from cohort, cross-sectional, and case-control studies, and the outcomes examined included Alzheimer's disease, vascular dementia, nonspecified dementia, all dementias, and cognitive decline or cognitive impairment. Education, occupation, and leisure or mentally stimulating activities were suggested to supply cognitive reserve and offer a protective effect against the risk of dementia. Premorbid IQ and socioeconomic status have not been investigated as thoroughly and showed inconsistent results. Two of the reviews showed that when combining different indicators in the analyses/definition, including education, occupation, mentally stimulating activities, and premorbid IQ, cognitive reserve had a protective effect against cognitive decline. However, other indicators may also supply the reserve, including dietary habits and genetic indicators, but research is lacking with regard to creating a full cognitive reserve model.

CONCLUSIONS

This review highlights the lack of consensus regarding a definition of cognitive reserve. Further research is required to clarify how the indicators already identified may provide cognitive reserve and offer a protective effect against dementia. Agreement on the indicators that constitute the cognitive reserve model is needed before testing possible interventions that may increase the reserve supply and improve cognition.

Going outdoors and cognitive function among community-dwelling older adults: Moderating role of physical function

AIMS

Identifying the risk factors of cognitive impairment is essential for implementing effective prevention strategies for dementia. Previous studies have shown that the frequency of going outdoors is inversely associated with cognitive decline. Little research has examined whether the relationship between going outdoors and cognitive decline varies with physical functioning in older adults. The aim of the present study was to examine the relationship between going outdoors and cognitive function in older adults with and without physical function limitations.

METHODS

The present study analyzed the data of 4450 individuals (aged 65 years or older) who participated in the Obu Study of Health Promotion for the Elderly. The measures were the Mini-Mental State Examination (MMSE), going outdoors (at least once a week or not), self-reported physical function limitations (with or without), and demographic and health-related factors as potential confounders.

RESULTS

Analysis of covariance and post-hoc comparisons showed that although going outdoors at least once a week was associated with higher MMSE scores among older adults with limited physical function, it was not significantly associated with the MMSE scores among older adults without limited physical function. Similarly, logistic regression analyses, stratified by physical function, showed a significant association between going outdoors and MMSE (<24 points or not) among older adults with limited physical function.

CONCLUSIONS

The results show that going outdoors less than once a week is associated with decreased cognitive function among older adults with limited physical function, but it is not associated with cognitive function among older adults without limited physical function.

Development and validation of a brief dementia screening indicator for primary care

BACKGROUND

Detection of "any cognitive impairment" is mandated as part of the Medicare annual wellness visit, but screening all patients may result in excessive false positives.

METHODS

We developed and validated a brief Dementia Screening Indicator using data from four large, ongoing cohort studies (the Cardiovascular Health Study [CHS]; the Framingham Heart Study [FHS]; the Health and Retirement Study [HRS]; the Sacramento Area Latino Study on Aging [SALSA]) to help clinicians identify a subgroup of high-risk patients to target for cognitive screening.

RESULTS

The final Dementia Screening Indicator included age (1 point/year; ages, 65-79 years), less than 12 years of education (9 points), stroke (6 points), diabetes mellitus (3 points), body mass index less than 18.5 kg/m(2) (8 points), requiring assistance with money or medications (10 points), and depressive symptoms (6 points). Accuracy was good across the cohorts (Harrell's C statistic: CHS, 0.68; FHS, 0.77; HRS, 0.76; SALSA, 0.78).

CONCLUSIONS

The Dementia Screening Indicator is a simple tool that may be useful in primary care settings to identify high-risk patients to target for cognitive screening.

Cognitive impairment in individuals with low educational level and homogeneous sociocultural background

Prevalence studies of dementia and cognitive impairment in different cultures and environments are necessary.

OBJECTIVE

To verify the prevalence of cognitive impairment and dementia in a rural homogeneous population from flooded areas in the Amazonian Basin.

METHODS

A total of 163 subjects were interviewed with neurological, cognitive and functional evaluation. The individuals were classified as demented or cognitive impairment no dementia (CIND).

RESULTS

cognitive impairment was observed in 11.4% (n=18 individuals). Ten out of the 18 were diagnosed as CIND and eight with dementia. The prevalence rate of dementia was 4.9% in subjects aged 50 years or over and of CIND was 6.1%. Considering only the elder group (>64 years of age), there was a 12.3% prevalence of dementia and 7.7% of CIND.

CONCLUSION

In a homogeneous population, we observed a similar prevalence of dementia to rates reported by studies in Brazil and in other developed and developing countries.

Alcohol consumption and cognitive performance: a Mendelian randomization study

AIMS

To use Mendelian randomization to assess whether alcohol intake was causally associated with cognitive function.

DESIGN

Mendelian randomization using a genetic variant related to alcohol intake (ADH1B rs1229984) was used to obtain unbiased estimates of the association between alcohol intake and cognitive performance.

SETTING

Europe.

PARTICIPANTS

More than 34 000 adults.

MEASUREMENTS

Any versus no alcohol intake and units of intake in the previous week was measured by questionnaire. Cognitive function was assessed in terms of immediate and delayed word recall, verbal fluency and processing speed.

FINDINGS

Having consumed any versus no alcohol was associated with higher scores by 0.17 standard deviations (SD) [95% confidence interval (CI) = 0.15, 0.20] for immediate recall, 0.17 SD (95% CI = 0.14, 0.19) for delayed recall, 0.17 SD (95% CI = 0.14, 0.19) for verbal fluency and 0.12 SD (95% CI = 0.09, 0.15) for processing speed. The minor allele of rs1229984 was associated with reduced odds of consuming any alcohol (odds ratio = 0.87; 95% CI = 0.80, 0.95; P = 0.001; R(2)  = 0.1%; F-statistic = 47). In Mendelian randomization analysis, the minor allele was not associated with any cognitive test score, and instrumental variable analysis suggested no causal association between alcohol consumption and cognition: -0.74 SD (95% CI = -1.88, 0.41) for immediate recall, -1.09 SD (95% CI = -2.38, 0.21) for delayed recall, -0.63 SD (95% CI = -1.78, 0.53) for verbal fluency and -0.16 SD (95% CI = -1.29, 0.97) for processing speed.

CONCLUSIONS

The Mendelian randomization analysis did not provide strong evidence of a causal association between alcohol consumption and cognitive ability.

Age-correction of test scores reduces the validity of mild cognitive impairment in predicting progression to dementia

Objectives

A phase of mild cognitive impairment (MCI) precedes most forms of neurodegenerative dementia. Many definitions of MCI recommend the use of test norms to diagnose cognitive impairment. It is, however, unclear whether the use of norms actually improves the detection of individuals at risk of dementia. Therefore, the effects of age- and education-norms on the validity of test scores in predicting progression to dementia were investigated.

Methods

Baseline cognitive test scores (Syndrome Short Test) of dementia-free participants aged ≥65 were used to predict progression to dementia within three years. Participants were comprehensively examined one, two, and three years after baseline. Test scores were calculated with correction for (1) age and education, (2) education only, (3) age only and (4) without correction. Predictive validity was estimated with Cox proportional hazard regressions. Areas under the curve (AUCs) were calculated for the one-, two-, and three-year intervals.

Results

82 (15.3%) of initially 537 participants, developed dementia. Model coefficients, hazard ratios, and AUCs of all scores were significant (p<0.001). Predictive validity was the lowest with age-corrected scores (−2 log likelihood  = 840.90, model fit χ² (1)  = 144.27, HR  = 1.33, AUCs between 0.73 and 0.87) and the highest with education-corrected scores (−2 log likelihood  = 815.80, model fit χ² (1)  = 171.16, HR  = 1.34, AUCs between 0.85 and 0.88).

Conclusion

The predictive validity of test scores is markedly reduced by age-correction. Therefore, definitions of MCI should not recommend the use of age-norms in order to improve the detection of individuals at risk of dementia.

The association between educational level and dementia in rural Tanzania

The majority of people with dementia worldwide live in developing countries. Studies from the developed world have reported an association between lower educational attainment and dementia, but there are few data from the developing world where literacy and educational levels are frequently much lower. In this study we assessed the association between education and dementia prevalence in a rural Tanzanian setting.

Methods

In phase I, 1198 individuals aged 70 and over were assessed using the Community Screening Instrument for Dementia (CSI-D). In phase Ii a stratified sample of those seen in phase I were fully assessed and a clinical diagnosis based on DSM-IV criteria was made where appropriate. Information regarding literacy, highest attained educational level and occupation were also collected.

Results

The median subject cognitive score on the CSI-D was 25.7 (IQR 22.7 to 28.0) for females and 27.7 (IQR 25.7 to 29.4) for males. This difference was significant (U=117770.0, z= -9.880, p<0.001). In both males and females a lower CSI-D subject cognitive score was significantly associated with having had no formal education (U=34866.5, z= -6.688, p<0.001, for females; U=20757.0, z= -6.278, p<0.001, for males). After adjusting for the effect of age, having no formal education was significantly associated with greater odds of having 'probable dementia' by CSI-D, as was illiteracy. Amongst those interviewed in phase II, there was no significant difference in literacy or education between those with diagnosed DSM-IV dementia and those without.

Conclusion

In this rural Tanzanian population, we found a significant association between low levels of education and dementia by CSI-D. This relationship was not significant in cases meeting DSM-IV criteria for dementia.

Prevalence of dementia and subtypes in Valladolid, northwestern Spain: the DEMINVALL study

OBJECTIVE

To describe the prevalence of dementia and subtypes in a general elderly population in northwestern Spain and to analyze the influence of socio-demographic factors.

METHODS

Cross-sectional, two-phase, door-to-door, population-based study. A total of 870 individuals from a rural region and 2,119 individuals from an urban region of Valladolid, Spain, were involved. The seven-minute screen neurocognitive battery was used in the screening phase. A control group was included.

RESULTS

A total of 2,170 individuals aged 65 to 104 years (57% women) were assessed. There were 184 subjects diagnosed with dementia. The crude prevalence was 8.5% (95% CI: 7.3-9.7). Age- and sex-adjusted prevalence was 5.5 (95% CI: 4.5-6.5). Main subtypes of dementia were: Alzheimer's disease (AD) 77.7%, Lewy Body disease, 7.6% and vascular dementia (VD) 5.9%. Crude prevalences were 6.6% (AD), 0.6% (Lewy Body disease), and 0.5% (VD). Dementia was associated with age (OR 1.14 for 1-year increase in age), female sex (OR 1.79) and the absence of formal education (OR 2.53 compared to subjects with primary education or more).

CONCLUSION

The prevalence of dementia in the study population was lower than the most recent estimates for Western Europe. There was a high proportion of AD among all dementia cases and very low prevalence of VD. Old age, female sex, and low education level were independent risk factors for dementia and AD.

Effects of education on very mild dementia among Chinese people in Hong Kong: potential mediators in the Cantonese Mini-Mental State Examination tasks

BACKGROUND

In Hong Kong, older Chinese adults generally have a low level of education. This study examined the effect of education on very mild Alzheimer's disease (AD), as quantified by Clinical Dementia Rating (CDR) scale (CDR 0.5 versus 0), in a Chinese community. The Cantonese version of the Mini-Mental State Examination (C-MMSE) was used to estimate cognitive abilities that were related to the level of education, and that in turn serve as protective factors for AD.

METHODS

A total of 788 community-dwelling older adults (383 CDR 0 and 405 CDR 0.5) were recruited in this cross-sectional study, which was derived from a population-based prevalence project. The participants' number of years of education and C-MMSE scores were used to predict their CDR scores using logistic regression and the mediation effects of C-MMSE scores were analyzed.

RESULTS

Consistent with previous studies, the chance of being rated as having very mild AD increased with age, but decreased with years of education, among the older adult community of Hong Kong. The effect of education on very mild dementia was weakened substantially when C-MMSE scores were included as mediating variables.

CONCLUSIONS

The findings indicate that the protective effects of education on dementia were mediated by an enhancement of older adults' performance on some C-MMSE items, including attention and orientation to time and place.

Effects of education on cognition at older ages: evidence from China's Great Famine

This paper explores whether educational attainment has a cognitive reserve capacity in elder life. Using pilot data from the China Health and Retirement Longitudinal Study (CHARLS), we examined the impact of education on cognitive abilities at old ages. OLS results showed that respondents who completed primary school obtained 18.2 percent higher scores on cognitive tests than those who did not. We then constructed an instrumental variable (IV) by leveraging China's Great Famine of 1959-1961 as a natural experiment to estimate the causal effect of education on cognition. Two-stage least squares (2SLS) results provided sound evidence that completing primary school significantly increases cognition scores, especially in episode memory, by almost 20 percent on average. Moreover, Regression Discontinuity (RD) analysis provides further evidence for the causal interpretation, and shows that the effects are different for the different measures of cognition we explored. Our results also show that the Great Famine can result in long-term health consequences through the pathway of losing educational opportunities other than through the pathway of nutrition deprivation.

Development of a new method for assessing global risk of Alzheimer's disease for use in population health approaches to prevention

Alzheimer's disease (AD) affects approximately 35 million people worldwide. Increasing evidence suggests that many risk factors for AD are modifiable. AD pathology develops over decades. Hence risk reduction interventions require very long follow-ups to show effects on AD incidence. Focussing on AD risk, instead of diagnosis, provides a more realistic target for prevention strategies. We developed a novel methodology that yields a global approach to risk assessment for AD for use in population-based settings and interventions. The methodology was used to develop a risk assessment tool that can be updated as more evidence becomes available. First, a systematic search strategy identified risk and protective factors for AD. Eleven risk factors and four protective factors for AD were identified for which odds ratios were published or could be calculated (age, sex, education, body mass index, diabetes, depression, serum cholesterol, traumatic brain injury, smoking, alcohol intake, social engagement, physical activity, cognitive activity, fish intake, and pesticide exposure). An algorithm was developed to combine the odds ratios into an AD risk score. The approach allows for interactions among risk factors which provides for their varying impact over the life-course as current evidence suggests midlife is a critical period for some risk factors. Finally, a questionnaire was developed to assess the risk and protective factors by self-report. Compared with developing risk indices on single cohort studies, this approach allows for more risk factors to be included, greater generalizeability of results, and incorporation of interactions based on findings from different stages of the lifecourse.

Chronic diseases, cognition, functional decline, and the Charlson index in elderly people with dementia

OBJECTIVE

To assess the association between chronic degenerative diseases and functional decline, cognition, and mortality prediction.

METHODS

A cross-sectional study was conducted in a geriatrics service in Belo Horizonte, Brazil, involving 424 patients subdivided into two groups: control and dementia. The study analyzed socio-demographic and environmental data, chronic degenerative diseases, the Charlson index, and data on functional and cognitive dementia.

RESULTS

After a univariate analysis, there was a greater frequency of cerebrovascular accident (CVA), urinary incontinence, constipation, and sleep disorder in the dementia group, while the multivariate analysis showed a greater number of environmental factors and sleep disorder. Regarding the Mini Mental State Examination (MMSE), patients with chronic obstructive pulmonary disease (COPD), CVA, and heart failure presented lower scores. There was a greater score in the dementia group with regarding the Charlson index.

CONCLUSION

These comorbidities were associated with the functional decline in elderly people with dementia.

Inhaled sevoflurane may promote progression of amnestic mild cognitive impairment: a prospective, randomized parallel-group study

BACKGROUND

Amnestic mild cognitive impairment (aMCI) is thought to be a transitional stage between normal aging and the development of Alzheimer's disease (AD). Recent studies have suggested that the inhalational anesthetic isoflurane can induce caspase activation and apoptosis, increase aggregates of β-amyloid (Aβ) levels, and enhance Aβ aggregation. The aim of this study was to investigate whether previous exposure to different anesthetics induced progression of aMCI.

METHODS

A prospective, randomized parallel-group study was completed with 180 patients with aMCI who were randomly assigned to a sevoflurane, propofol or lidocaine epidural anesthesia group (n = 60 per group) during an L3 to L4 or an L4 to L5 spinal surgery. Sixty additional outpatients with aMCI served as a control group. Before surgery, all subjects underwent a neuropsychological assessment. Cerebrospinal fluid (CSF) was obtained by lumbar puncture, and neuropsychological assessments were completed in the clinic. CSF Aβ42, total tau and phosphorylated tau181 were quantitatively assayed. The neuropsychological assessments were repeated after 2 years.

RESULTS

Two years after anesthesia, the number of AD cases that emerged did not differ significantly between the groups. However, the number of cases of progressive MCI was greater in the sevoflurane group than in the control group. Age correlated linearly with aMCI progression, whereas sex did not. Both patients with AD and progressive MCI had decreased CSF Aβ42, increased total tau and increased phosphorylated tau levels compared with those with stable MCI and the controls.

CONCLUSIONS

Inhaled sevoflurane accelerated the progression of aMCI to progressive MCI in this selected Chinese population.

Epidemiology of dementias and Alzheimer's disease

BACKGROUND AND AIMS

Global population aging has been one of the defining processes of the twentieth century, with profound economic, political and social consequences. It is driving the current epidemic of dementia, both in terms of its extent and global distribution. The aim of the study was to summarize recent findings relevant to the epidemiological knowledge of dementia and Alzheimer's disease (AD).

METHODS

A narrative mini-review of the literature relevant to the epidemiology of dementia and AD is presented, summarizing important findings and analyzing their implications.

RESULTS

It was estimated that in 2010 there were 36.5 million people living with dementia, with 7.7 million new cases yearly and a new case of dementia every 4 sec. The number of persons living with dementia will nearly double every 20 years. Most of these persons will be living in low- and middle-income countries (LMIC).

CONCLUSIONS

There are a substantial number of people with dementia worldwide and these numbers will continue to increase mainly in LMIC, producing a wide range of impacts. It is important to make dementia a national public health and social care priority worldwide. Recent reviews and meta-analyses have failed to clearly identify a singular causal or preventive pathway for AD that seems to be a multicausal, heterogeneous and age-related condition.

Virtual navigation strategies from childhood to senescence: evidence for changes across the life span

This study sought to investigate navigational strategies across the life span, by testing 8-years old children to 80-years old healthy older adults on the 4 on 8 virtual maze (4/8VM). The 4/8VM was previously developed to assess spontaneous navigational strategies, i.e., hippocampal-dependent spatial strategies (navigation by memorizing relationships between landmarks) versus caudate nucleus-dependent response strategies (memorizing a series of left and right turns from a given starting position). With the 4/8VM, we previously demonstrated greater fMRI activity and gray matter in the hippocampus of spatial learners relative to response learners. A sample of 599 healthy participants was tested in the current study. Results showed that 84.4% of children, 46.3% of young adults, and 39.3% of older adults spontaneously used spatial strategies (p < 0.0001). Our results suggest that while children predominantly use spatial strategies, the proportion of participants using spatial strategies decreases across the life span, in favor of response strategies. Factors promoting response strategies include repetition, reward and stress. Since response strategies can result from successful repetition of a behavioral pattern, we propose that the increase in response strategies is a biological adaptive mechanism that allows for the automatization of behavior such as walking in order to free up hippocampal-dependent resources. However, the down-side of this shift from spatial to response strategies occurs if people stop building novel relationships, which occurs with repetition and routine, and thereby stop stimulating their hippocampus. Reduced fMRI activity and gray matter in the hippocampus were shown to correlate with cognitive deficits in normal aging. Therefore, these results have important implications regarding factors involved in healthy and successful aging.

Relationship between education and dementia: an updated systematic review

OBJECTIVE

The purpose of this study was to review the relationship between education and dementia.

METHODS

A systematic literature review was conducted of all published studies examining the relationship between education and dementia listed in the PubMed and PsycINFO databases from January 1985 to July 2010. The inclusion criteria were a measure of education and a dementia diagnosis by a standardized diagnostic procedure. Alzheimer disease and Total Dementia were the outcomes.

RESULTS

A total of 88 study populations from 71 studies met inclusion criteria. Overall, 51 studies (58%) reported significant effects of lower education on risk for dementia, whereas 37 studies (42%) reported no significant relationship. A relationship between education and risk for dementia was more consistent in developed regions compared with developing regions. Age, sex, race/ethnicity, and geographical region moderated the relationship.

CONCLUSIONS

Lower education was associated with a greater risk for dementia in many but not all studies. The level of education associated with risk for dementia varied by study population and more years of education did not uniformly attenuate the risk for dementia. It seemed that a more consistent relationship with dementia occurred when years of education reflected cognitive capacity, suggesting that the effect of education on risk for dementia may be best evaluated within the context of a lifespan developmental model.

[Reading as a protective factor against cognitive decline]

OBJECTIVE

To determine whether reading is a protective factor against cognitive decline in the population aged over 65 years.

METHODS

We performed an unmatched case-control study in the Fuente de San Luis Health Center in Valencia, Spain. A total of 153 subjects aged more than 65 years old were studied, corresponding to 51 cases and 102 controls. Cognitive impairment was measured by the version of the Mini-Mental State Examination adapted and validated to Spanish. Reading habits were assessed with the scale of the Federación de Gremios y Editores de España.

RESULTS

Logistic regression showed a significant association with the habit of frequent reading for more than 5 years, complete primary school education, and age lower than 75 years

CONCLUSIONS

Reading is a protective factor against cognitive impairment. This protection is greater in frequent readers with a history of reading of over 5 years.

ACTIVE cognitive training and rates of incident dementia

Systematic cognitive training produces long-term improvement in cognitive function and less difficulty in performing activities of daily living. We examined whether cognitive training was associated with reduced rate of incident dementia. Participants were from the Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) study (n = 2,802). Incident dementia was defined using a combination of interview- and performance-based methods. Survival analysis was used to determine if ACTIVE treatment affected the rate of incident dementia during 5 years of follow-up. A total of 189 participants met criteria for incident dementia. Baseline factors predictive of incident dementia were older age, male gender, African American race, fewer years of education, relationship other than married, no alcohol use, worse MMSE, worse SF-36 physical functioning, higher depressive symptomatology, diabetes, and stroke (all p < .05). A multivariable model with significant predictors of incident dementia and training group revealed that cognitive training was not associated with a lower rate of incident dementia. Cognitive training did not affect rates of incident dementia after 5 years of follow-up. Longer follow-up or enhanced training may be needed to fully explore the preventive capacity of cognitive training in forestalling onset of dementia.

Environmental risk factors for REM sleep behavior disorder: a multicenter case-control study

OBJECTIVE

Idiopathic REM sleep behavior disorder is a parasomnia characterized by dream enactment and is commonly a prediagnostic sign of parkinsonism and dementia. Since risk factors have not been defined, we initiated a multicenter case-control study to assess environmental and lifestyle risk factors for REM sleep behavior disorder.

METHODS

Cases were patients with idiopathic REM sleep behavior disorder who were free of dementia and parkinsonism, recruited from 13 International REM Sleep Behavior Disorder Study Group centers. Controls were matched according to age and sex. Potential environmental and lifestyle risk factors were assessed via standardized questionnaire. Unconditional logistic regression adjusting for age, sex, and center was conducted to investigate the environmental factors.

RESULTS

A total of 694 participants (347 patients, 347 controls) were recruited. Among cases, mean age was 67.7 ± 9.6 years and 81.0% were male. Cases were more likely to smoke (ever smokers = 64.0% vs 55.5%, adjusted odds ratio [OR] = 1.43, p = 0.028). Caffeine and alcohol use were not different between cases and controls. Cases were more likely to report previous head injury (19.3% vs 12.7%, OR = 1.59, p = 0.037). Cases had fewer years of formal schooling (11.1 ± 4.4 years vs 12.7 ± 4.3, p < 0.001), and were more likely to report having worked as farmers (19.7% vs 12.5% OR = 1.67, p = 0.022) with borderline increase in welding (17.8% vs 12.1%, OR = 1.53, p = 0.063). Previous occupational pesticide exposure was more prevalent in cases than controls (11.8% vs 6.1%, OR = 2.16, p = 0.008).

CONCLUSIONS

Smoking, head injury, pesticide exposure, and farming are potential risk factors for idiopathic REM sleep behavior disorder.

Education and dementia in the context of the cognitive reserve hypothesis: a systematic review with meta-analyses and qualitative analyses

Background

Cognitive reserve (CR) or brain reserve capacity explains why individuals with higher IQ, education, or occupational attainment have lower risks of developing dementia, Alzheimer’s disease (AD) or vascular dementia (VaD). The CR hypothesis postulates that CR reduces the prevalence and incidence of AD or VaD. It also hypothesizes that among those who have greater initial cognitive reserve (in contrast to those with less reserve) greater brain pathology occurs before the clinical symptoms of disease becomes manifest. Thus clinical disease onset triggers a faster decline in cognition and function, and increased mortality among those with initial greater cognitive reserve. Disease progression follows distinctly separate pathological and clinical paths. With education as a proxy we use meta-analyses and qualitative analyses to review the evidence for the CR hypothesis.

Methodology/Principal Findings

We searched PubMed, PsycoINFO, EMBASE, HealthStar, and Scopus databases from January 1980 to June 2011 for observational studies with clear criteria for dementia, AD or VaD and education. One hundred and thirty-three articles with a variety of study designs met the inclusion criteria. Prevalence and incidence studies with odds ratios (ORs), relative risks or original data were included in the meta-analyses. Other studies were reviewed qualitatively. The studies covered 437,477 subjects. Prevalence and incidence studies with pooled ORs of 2.61 (95%CI 2.21–3.07) and 1.88 (95%CI 1.51–2.34) respectively, showed low education increased the risk of dementia. Heterogeneity and sensitivity tests confirmed the evidence. Generally, study characteristics had no effect on conclusions. Qualitative analyses also showed the protective effects of higher education on developing dementia and with clinical disease onset hastening a decline in cognition and function, and greater brain pathology.

Conclusion/Significance

This systematic review and meta-analyses covering a wide range of observational studies and diverse settings provides robust support for the CR hypothesis. The CR hypothesis suggests several avenues for dementia prevention.

Prospective and Retrospective Memory Complaints in Mild Cognitive Impairment and Mild Alzheimer's Disease

Current management attempts for Alzheimer's disease (AD) focus on the identification of individuals in the preclinical stage. This has led to the development of the diagnostic concept of Mild Cognitive Impairment (MCI), which applies to individuals with declining cognitive abilities but largely preserved everyday functioning. Previous findings indicate that prospective memory deficits are a sensitive marker of preclinical AD and that awareness of prospective memory failures is particularly high, based on its dependence on executive functions. Thus, the goal of this study was to evaluate the usefulness of subjective prospective versus retrospective memory complaints for an initial screening for MCI and their respective associations with executive functions. 71 healthy older adults, 27 MCI patients, and 9 patients with mild AD completed the Prospective and Retrospective Memory Questionnaire (PRMQ) and three executive functions tests. The healthy and the MCI group could not be distinguished by their level of subjective prospective or retrospective memory complaints, but the mild AD patients differed from the other groups by complaining more about retrospective than prospective memory failures. For the healthy older adults, the prospective memory complaints were correlated to an inhibition test, whereas they did not correlate with any of the executive function tests in the MCI patients. In contrast, in both groups the retrospective memory complaints were related to a task switching test. The findings are discussed with respect to differences between the three groups in cognitive abilities, attention to failures of, use of mnemonic aids for, and everyday demands of prospective and retrospective memory.

Socioeconomic status during lifetime and cognitive impairment no-dementia in late life: the population-based aging in the Chianti Area (InCHIANTI) Study

Thousand and twelve dementia-free elderly (60–98 years old) enrolled in the InChianti Study (Italy) were evaluated at baseline (1998–2000) and at 3-year follow-up (2001–2003) with the aim of analyzing the association of lifetime socioeconomic status (SES) with prevalent and incident cognitive impairment no-dementia (CIND). SES was defined from information on formal education, longest held occupation, and financial conditions through life. CIND was defined as age-adjusted Mini-Mental State Examination score one standard deviation below the baseline mean score of participants without dementia. Logistic regression and Cox proportional-hazards models were used to estimate the association of SES with CIND. Demographics,occupation characteristics (i.e., job stress and physical demand), cardiovascular diseases, diabetes, apolipoprotein E (APOE)genotype, smoking, alcohol consumption, depressive symptoms, and C-reactive protein were considered potential confounders.Prevalence of CIND was 17.7%. In the fully adjusted model, low education (OR = 2.1; 95% confidence intervals, CI = 1.4 to 3.2)was associated with prevalent CIND. Incidence rate of CIND was 66.0 per 1000 person-years. Low education (HR = 1.7; 95% CI = 1.04 to 2.6) and manual occupation (HR = 1.9; 95% CI = 1.0 to 3.6) were associated with incident CIND. Among covariates,high job-related physical demand was associated with both prevalent and incident CIND (OR = 1.6; 95% CI = 1.1 to 2.4 and HR= 1.5; 95% CI = 1.0 to 2.3). After stratification for education, manual occupation was still associated with CIND among participants with high education (HR = 2.2; 95% CI = 1.2 to 4.3 versus HR= 1.4; 95% CI = 0.2 to 10.4 among those with low education). Proxy markers of lifetime SES (low education, manual occupation and high physical demand) are cross-sectional correlates of CIND and predict incident CIND over a three-year follow-up.

Formal education, socioeconomic status, and the severity of aphasia after stroke

OBJECTIVE

To determine the role of education and socioeconomic status on the severity of aphasia after stroke.

DESIGN

Cross-sectional study.

SETTING

Stroke units of 2 affiliated medical centers.

PARTICIPANTS

Stroke patients (n=173) within 24 hours of symptom development and hospitalized controls (n=62) matched for age, education, and socioeconomic status (SES) with normative brain magnetic resonance imaging.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Percent error on 9 language tasks (auditory and written comprehension, naming [oral, written, and tactile], oral reading, oral spelling, written spelling, and repetition). Education was recorded in years and dichotomized as less than 12 years or 12 years and above for data analysis. Demographic characteristics (age, sex, race) and stroke volume were recorded for adjustment. SES was obtained from census tract data as 2 variables: mean neighborhood household income and family income.

RESULTS

The percentage of errors for participants with 12 or more years of education was significantly lower for auditory and written comprehension, written naming, oral reading, oral spelling, and written spelling of fifth grade vocabulary words, even after adjusting for age, sex, stroke volume, and SES.

CONCLUSIONS

These findings suggest that even once learned, access to written word forms may become less vulnerable to disruption by stroke with increasing years of education.

A life course model of cognitive activities, socioeconomic status, education, reading ability, and cognition

OBJECTIVES

To cross-sectionally quantify the contribution of proxy measures of cognitive reserve reflective of the lifespan, such as education, socioeconomic status (SES), reading ability, and cognitive activities, in explaining late-life cognition.

DESIGN

Prospective observational cohort study of aging.

SETTING

Retirement communities across the Chicago metropolitan area.

PARTICIPANTS

Nine hundred fifty-one older adults free of clinical dementia in the Rush Memory and Aging Project (aged 79 ± 8, 74% female).

MEASUREMENTS

Baseline data on multiple life course factors included early-, mid-, and late-life participation in cognitive activities; early-life and adult SES; education; and reading ability (National Adult Reading Test; NART). Path analysis quantified direct and indirect standardized effects of life course factors on global cognition and five cognitive domains (episodic memory, semantic memory, working memory, visuospatial ability, perceptual speed).

RESULTS

Adjusting for age, sex, and race, education had the strongest association with global cognition, episodic memory, semantic memory, and visuospatial ability, whereas NART (followed by education) had the strongest association with working memory. Late-life cognitive activities had the strongest association with perceptual speed, followed by education.

CONCLUSIONS

These cross-sectional findings suggest that education and reading ability are the most-robust proxy measures of cognitive reserve in relation to late-life cognition. Additional research leveraging path analysis is warranted to better understand how these life course factors, reflecting the latent construct of cognitive reserve, affect abnormal cognitive aging.

The projected effect of risk factor reduction on Alzheimer's disease prevalence

At present, about 33·9 million people worldwide have Alzheimer's disease (AD), and prevalence is expected to triple over the next 40 years. The aim of this Review was to summarise the evidence regarding seven potentially modifiable risk factors for AD: diabetes, midlife hypertension, midlife obesity, smoking, depression, cognitive inactivity or low educational attainment, and physical inactivity. Additionally, we projected the effect of risk factor reduction on AD prevalence by calculating population attributable risks (the percent of cases attributable to a given factor) and the number of AD cases that might be prevented by risk factor reductions of 10% and 25% worldwide and in the USA. Together, up to half of AD cases worldwide (17·2 million) and in the USA (2·9 million) are potentially attributable to these factors. A 10-25% reduction in all seven risk factors could potentially prevent as many as 1·1-3·0 million AD cases worldwide and 184,000-492,000 cases in the USA.