Rates and risk factors for dementia and Alzheimer's disease: results from EURODEM pooled analyses. EURODEM Incidence Research Group and Work Groups. European Studies of Dementia

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.

Risk factors and early signs of Alzheimer's disease in a family study sample. Risk of AD

OBJECTIVE

Several predictors of Alzheimer's disease (AD) have been identified. However, the relevance and independent contribution of risk factors and of possible early signs such as mild cognitive impairment and subjective memory impairment on the development of AD has not been investigated prospectively in a cohort of non-demented elderly including first-degree relatives of AD subjects.

METHOD

The development of AD was investigated in 757 non-demented elderly. Initial diagnoses were made from personal interviews. Information on 633 subjects after 4.7 +/- 1.2 years (mean +/- SD) was obtained either from personal or family history interviews. Using forward logistic regression analysis, predictors were identified by comparing their presence in 38 subjects who developed AD and 577 subjects who remained non-demented.

RESULTS

The most important predictors of later Alzheimer's disease were increased age (Odds ratio OR = 1.086/additional year, p < 0.001), initial subjective memory complaints (OR = 2.68, p = 0.019), initial mild cognitive impairment (OR = 2.51, p = 0.032) and female gender (OR = 2.84, p = 0.069). Exploratory analysis revealed that previous depression after the age of 60 years (OR = 2.37, p = 0.033) and the presence of the apolipoprotein E4 allele (OR = 2.49, p = 0.043) individually predicted new AD during follow-up. A positive family history of AD (i. e. being a first degree relative of a subject suffering from AD) did not significantly influence the development of AD (p > 0.2).

CONCLUSIONS

Increased age, the presence of mild cognitive impairment, subjective memory impairment and gender are the most relevant independent predictors of later Alzheimer's disease that may be used in combination for clinical prediction of AD.

Very early detection of Alzheimer neuropathology and the role of brain reserve in modifying its clinical expression

Numerous studies show that the pathology of Alzheimer's disease is present decades before a clinical diagnosis of dementia can be made. Given the likelihood that agents will become available that reliably delay onset and/or slow progression of Alzheimer's disease, it will be important to detect preclinical Alzheimer's disease as early as possible for maximal treatment effect. Detection of individuals by sensitive cognitive measures provides one way to identify people who are at high risk of developing clinical Alzheimer's disease. However, it is likely that those with considerable brain or cognitive reserve will be able to mask cognitive deficits until very close to the onset of the dementia, rendering such cognitive measures insensitive. Optimum biomarkers for Alzheimer's disease therefore need to target the severity of underlying brain pathology independently of brain reserve. Findings are presented showing the importance of higher education and larger brain size in masking the underlying disease pathology.

Projections of future numbers of dementia cases in Australia with and without prevention

OBJECTIVE

To produce projections of the number of dementia cases in Australia from 2000 to 2050. These projections examine the effects of an ageing population on number of dementia cases and also the potential impact of preventive strategies that delay age of dementia onset.

METHOD

Data from several meta-analyses of dementia prevalence and incidence were combined with age-specific population projections to arrive at estimates of future numbers of cases. A statistical model of dementia incidence was developed and used to estimate the effects of delaying onset by up to 5 years.

RESULTS

Without prevention, prevalence of dementia is estimated to increase from 172 000 in 2000 to 588 000 in 2050. Over the same period, the incidence of dementia is estimated to increase from 43 000 to 143 000 new cases a year. Delaying onset by 5 years would decrease prevalence in 2050 by 44%. Even a 6-month delay would reduce prevalence by 6%.

CONCLUSIONS

Ageing of the population will lead to a rapid increase in number of dementia cases and an increasing burden for the working-age population. However, even modest prevention efforts could lessen the impact.

Virtual reality in brain damage rehabilitation: review

Given the high incidence of brain injury in the population, brain damage rehabilitation is still a relatively undeveloped field. Virtual reality (VR) has the potential to assist current rehabilitation techniques in addressing the impairments, disabilities, and handicaps associated with brain damage. The main focus of much of the exploratory research performed to date has been to investigate the use of VR in the assessment of cognitive abilities, but there is now a trend for more studies to encompass rehabilitation training strategies. This review describes studies that have used VR in the assessment and rehabilitation of specific disabilities resulting from brain injury, including executive dysfunction, memory impairments, spatial ability impairments, attention deficits, and unilateral visual neglect. In addition, it describes studies that have used VR to try to offset some of the handicaps that people experience after brain injury. Finally, a table is included which, although not an exhaustive list of everything that has been published, includes many more studies that are relevant to the use of VR in the assessment and rehabilitation of brain damage. The review concludes that the use of VR in brain damage rehabilitation is expanding dramatically and will become an integral part of cognitive assessment and rehabilitation in the future.

The incidence of dementia in England and Wales: findings from the five identical sites of the MRC CFA Study

BACKGROUND

Although incidence of dementia is known to vary between nations, variation within country has not been explored because most incidence studies are single site or have insufficient numbers to compare sites. Few countries have conducted multisite incidence studies in order to facilitate national comparisons. This study aims to provide robust measures of the variation of the incidence of dementia across sites within England and Wales and produce overall estimates by age and sex.

METHODS AND FINDINGS

The Medical Research Council Cognitive Function and Ageing Study used identical methodology in five diverse sites across the United Kingdom, each with different risk patterns and mortality rates. Incidence has been estimated using likelihood-based methods between the first two waves of interviews. Incidence rates rise with age, particularly above the age of 75 y, from 6.7 [corrected] (95% confidence interval, 3.8 [corrected]-12.4 [corrected]) per 1,000 person years at age 65-69 y to 68.5 [corrected] (95% confidence interval, 52.5 [corrected]-88.1 [corrected]) per 1,000 person years at age 85 y and above. The rate of increase for both sexes is marked, and continues into the oldest age groups. Hence, it is estimated that approximately 163,000 [corrected] new cases of dementia occur in England and Wales each year. There is no convincing evidence of variation across sites, and incidence rates do not reflect the variations in the prevalence of possible risk factors in these sites.

CONCLUSION

There is no evidence, within England and Wales, of variation in dementia incidence across sites. Dementia incidence rates do not tail off at the oldest ages.

Physical activity and hormone-replacement therapy: interactive effects on cognition?

The purpose of this study was to examine the interactive effects of hormone-replacement therapy (HRT) and physical activity (PA) on the cognitive performance of older women. Postmenopausal women (n = 101) were recruited to complete a PA questionnaire, provide demographic information, and perform the digit-symbol substitution task (DSST) and the trail-making tests (TMT). Regression analyses were conducted for participants with complete data for each cognitive test (DSST n = 62; TMT n = 69). For both tasks, results indicated that PA and education were positively related and age was negatively related to cognitive performance. The interaction of HRT with PA did not add to the predicted variance of either measure of cognitive performance. This was true even after limiting the HRT users to women using unopposed estrogen. It is concluded that the beneficial relationship between PA and these two measures of cognitive performance in postmenopausal women exists irrespective of HRT use.

The synthetic estrogen 4-estren-3α,17β-diol (estren) induces estrogen-like neuroprotection

Estrogen has demonstrated neuroprotective properties, which may underlie the observed preventive effect of estrogen-based hormone therapy (HT) against the development of neurodegenerative disorders such as Alzheimer's disease. Deleterious side effects of HT have increased efforts to develop safer compounds that selectively reproduce beneficial estrogen actions. Recently, 4-estren-3 alpha,17 beta-diol (estren) was identified as having estrogen agonist properties in bone, without significantly stimulating growth of reproductive tissues. Here, we examined whether estren parallels the neuroprotective actions of estrogen against beta-amyloid (A beta) in cultured cerebrocortical neurons. Estren increased neuronal viability to a similar extent to that observed with 17 beta-estradiol (E2) and 17 alpha-estradiol. As we previously reported for E2, estren rapidly increased PKC activity, and PKC inhibition prevented estren neuroprotection. In contrast, the estrogen receptor antagonist ICI 182,780 blocked E2, but not estren neuroprotection. Our results indicate that estren-induced activation of rapid cell signaling pathways protects cultured neurons from A beta toxicity.

Correlates of regular fish consumption in French elderly community dwellers: data from the Three-City study

OBJECTIVE

Several studies have found an inverse association between fish consumption and risk of dementia. The objective of this study was to describe the characteristics of older fish consumers, in order to identify potential confounders in this relationship.

DESIGN

Cross-sectional analysis of the baseline data of a prospective cohort study.

SETTING

Bordeaux, Dijon, and Montpellier (France) in 1999-2000.

SUBJECTS

A total of 9280 community dwellers aged 65 y and above participating in the baseline examination of the Three-City Study.

INTERVENTIONS

All participants answered a face-to-face interview and underwent a physical examination. Cross-sectional analyses were performed by logistic regressions.

RESULTS

Regular fish consumers (at least weekly) had a higher education (OR from 1.19 to 1.65, P = 0.0003) and income (OR from 1.37 to 1.89, P < 0.0001). Controlling for age, sex, education, and city, they had a higher consumption of pulses, fruit, and vegetables (P < 0.001). They were more often alcohol drinkers (P < 0.0001). They felt in better health (P < 0.05), exhibited less depressive symptoms (P < 0.001), and scored higher on the Mini Mental Status Examination (P < 0.05). However, their objective physical health status was not better, except that they were leaner. They suffered more often from hypertension and past stroke.

CONCLUSIONS

Socioeconomic status, dietary habits, depression, and vascular risk factors could act as confounders in the relationship between fish consumption and risk of dementia.

Neurodegenerative memory disorders: a potential role of environmental toxins

The hypothesis that neurotoxins may play a role in neurodegenerative disorders remains an elusive one, given that epidemiologic studies often provide conflicting results. Although these conflicting results may result from methodological differences within and between studies, the complexity of chemical disruption of the central nervous system cannot be ignored in attempts to evaluate this hypothesis in different neurodegenerative disorders. Spencer provides a detailed review of the complex processes involved in defining the neurotoxic potential of naturally occurring and synthetic agents. Even concepts such as exposure and dose, as often reported in studies attempting to evaluate the risk imparted by a potential compound, can be deceptive. For example, although dose reflects "that amount of chemical transferred to the exposed subject", factors such as time and concentration in the organism, the ability to access the central nervous system, and how a compound reaches the central nervous system (routes of administration) or secondarily affects other organ systems leading to central nervous system disruption are clearly important to the concept of neurotoxic risk in neurodegenerative disorders. These factors would appear to explain the observed disagreements between studies using animal or neuronal models of neurotoxicity and population-based studies in humans. The importance of these factors and how a potential neurotoxin is investigated are clearly seen in the data on AD and aluminum. In contrast, the impact of MTPT on the central nervous system is more direct and compelling. Added complexity in the study of neurotoxins in human neurodegeneration is derived from data showing that agents may have additive, potentiating, synergistic, or antagonistic effects. Therefore, data from studies evaluating EMF risks could be readily confounded by the presence or absence of heavy metals (eg, arc welding). Other factors that may conceal neurotoxic causes for a given disorder focus on additional features such as genetic predispositions, physiologic changes that occur in aging, and even nutritional status that can support or hinder the affect of a given agent on the central nervous system. Finally, many studies that investigate exposure risk do not readily incorporate the five criteria proposed by Schaumburg for establishing causation. For example, if we apply Schaumburg's first criterion, epidemiologic studies often determines the presence of an agent through history, yet they cannot readily confirm exposure based on environmental or clinical chemical analyses to fulfill this criterion for causation. Additional limitations in research design along with the populations and methods that are sued to study neurotoxins in human neurodegenerative disorders often fail to meet other criteria such as linking the severity and onset with duration and exposure level. Therefore, although studies of agents such as MTPT provide compelling models of neurotoxins and neurodegeneration in humans, disorders such as ALS, PD, and particularly AD will require additional effort if research is to determine the contribution (presence or absence) of neurotoxins to these neurologic disorders.

Short-term transdermal estradiol therapy, cognition and depressive symptoms in healthy older women. A randomised placebo controlled pilot cross-over study

The potential role of estrogen in protecting women from cognitive decline and reducing depressive symptoms is of great therapeutic interest. In a pilot randomised placebo controlled cross-over study, we aimed to determine the short-term effects of transdermal estradiol therapy on cognition and depressive symptoms in healthy cognitively normal post-menopausal women over 60 years of age. Nineteen cognitively normal women, without clinical depression whom had undergone a hysterectomy in the past were recruited. Women were randomised to receive either transdermal estradiol 50 microg/24 h (Femseven) or transdermal placebo for 12 weeks before crossing over to the other medication for a further 12 weeks. Cognition was assessed every 6 weeks by the cognitive drug research (CDR) computerised assessment which recorded both accuracy and speed in the following cognitive tests; simple reaction time, choice reaction time, digit vigilance, visual tracking, spatial working memory, immediate and delayed word recall and delayed face and picture recall. Depressive symptoms were measured using the brief assessment scale depression card (BASDEC) depression rating scale at baseline, 12 and 24 weeks. Participants had a mean age of 71, IQ of 115 and MMSE of 29. Simple reaction time and the BASDEC depression rating scale improved after 12 weeks of estradiol use. All other tests were unaltered by estradiol. Twelve weeks of transdermal estradiol therapy did not consistently improve the speed or accuracy of older women in various cognitive tests. However, the results do support the concept that depressive symptoms may be reduced by estradiol, and not simply due to the relief of climacteric symptoms.

Low blood pressure is a better predictor of cognitive deficits than the apolipoprotein e4 allele in the oldest old

OBJECTIVE

To study the correlates of cognitive deficits in persons 80 years and older.

MATERIALS AND METHODS

Data from 271 individuals between 80 and 102 years of age, drawn from a central registrar (response rate 50%) were analyzed regarding e apolipoprotein E (Apo-E) polymorphism, blood pressure (BP), homocysteine, sex, age and education as predictors for low score on Mini Mental Status Examination (MMSE).

RESULTS

Low systolic and diastolic BP were highly associated with low score on the MMSE, followed by age and Apo-E e4. No relationship was found between Apo-E allele groups and BP. Homocysteine, sex, and education were only of marginal importance.

CONCLUSIONS

Hypotension is an important factor for performance on the MMSE. To some extent, this was also true for having the Apo-E e4 allele. A combined effect on cognition for these two factors was not found.

Neuroprotective properties of selective estrogen receptor agonists in cultured neurons

To investigate the role of the estrogen receptor (ER) in mediating neuroprotection, the neuroprotective profiles of selective ER agonists for ERalpha and ERbeta, propylpyrazole triol (PPT) and 2,3-bis(4-hydroxyphenyl) proprionitrile (DPN), respectively, were compared to that of 17beta-estradiol and 17alpha-estradiol in primary neuron cultures challenged by beta-amyloid toxicity. All compounds were found to be neuroprotective in an ER-dependent manner. However, protein kinase C (PKC) inhibition completely blocked the protective effects of 17beta-estradiol and 17alpha-estradiol and significantly attenuated PPT but not DPN neuroprotection. These data indicate that estrogen-mediated neuroprotection likely involves a variety of mechanisms and that protection due to PKC activation is more likely due to ERalpha compared to ERbeta.

A combination of tests for the diagnosis of dementia had a significant diagnostic value

OBJECTIVE

To study the diagnostic parameters of a number of instruments for a diagnosis of dementia in general practice and the added diagnostic value of these tests.

STUDY DESIGN AND SETTING

Cross-sectional diagnostic research in general practice.

PARTICIPANTS

152 persons aged 65 plus. The Mini-Mental State Examination (MMSE), the Clock Drawing Test, the ADMP scale, the Timed Up and Go Test, the Extrapyramidal Sign Scale, the Behavior Observation Scale, the Poon-Baro-Wens computer battery, and the Cognitive Drug Research Computerized Assessment System were evaluated against the Dutch version of the Cambridge Examination for Mental Disorders of the Elderly (CAMDEX-N). Diagnostic characteristics were calculated with their 95% CI. Using forward stepwise logistic regression analysis, a model was built with CAMDEX-N as the dependent variable and the tests under study as independent variables. Area under the curve was the main parameter for the comparisons.

RESULTS

The main diagnostic gain results from age and ADMP, followed by the Clock Drawing Test. Subsequent addition of the MMSE and computer tests results in modest additional gain only. The final model including five tests has an area under the curve of 0.95.

CONCLUSION

Sophisticated neuropsychological computerized tests have little added value in the diagnostic work-up of dementia in general practice. Basic clinical tests used in an appropriate sequence can be very valuable in establishing the diagnosis of dementia.

Factors affecting timely recognition and diagnosis of dementia across Europe: from awareness to stigma

BACKGROUND

Timely recognition and diagnosis of dementia is the pre-condition for improving dementia care, but diagnosis often occurs late in the disease process.

OBJECTIVE

To compare facilitators and obstacles to the timely recognition of dementia across eight European Union states, in order to implement established policies for earlier diagnosis.

METHODS

A modified focus group technique, including a pre and posterior procedure.

RESULTS

Twenty-three participants from different disciplines, purposively sampled for professional expertise in dementia research and innovative practice, attended two focus groups. Stigma in ageing and dementia, accompanied by a sense that there is little to offer until later on in the disease, underpinned the widespread reluctance of GPs to recognise dementia at an early stage and were major obstacles to the timely diagnosis of dementia across all eight countries. Dementia care services varied widely across Europe. Countries with the greatest development of dementia health care services were characterised by national guidelines, GPs fulfilling a gatekeeper function, multi-disciplinary memory clinics and innovative programmes that stimulated practice and new services. Dementia-related stigma was perceived as being less prominent in these countries.

CONCLUSIONS

Overcome of delays in the timely diagnosis of dementia needs more than specialist services. They should address the processes associated with stigma, age and dementia, especially where these relate to physician practice and diagnostic disclosure. Stigma is perceived as variable across European States, with a promising finding that its impact is relatively small in countries with the widest range of dementia care services.

Fall-related brain injuries and the risk of dementia in elderly people: a population-based study

Severe head injury in early adulthood may increase the risk of dementia in older age, but it is not known whether head injury in later life also increases the risk of dementia. A representative sample (82%) of persons aged 70 years or older with a Mini-Mental State Examination (MMSE) test score of > or =26 (n = 325) were followed-up for 9 years to record all their fall-related head injuries resulting in traumatic brain injury (TBI). At the end of the follow-up period, 152 persons (81% of the surviving population) were examined for clinical dementia, according to DSM-IV criteria. Eight persons sustained a TBI and 34 developed dementia. Brain injury was associated with younger age at detection of dementia even when adjusted for sex and educational status (low educational status significantly associated with dementia); age-specific hazard ratio (95% confidence interval) 2.80 (1.35-5.81). In a population scoring > or =28 points in the baseline MMSE an apolipoprotein E (ApoE) epsilon4 phenotype was also associated with younger age at the time of detecting dementia; 3.56 (1.35-9.34), and the effect of brain injury and ApoE epsilon4 phenotype was synergistic; 7.68 (2.32-25.3). We conclude that fall-related TBI predicts earlier onset of dementia and the effect is especially high amongst subjects who carry the ApoE epsilon4 allele.

Calcium channel blockers and risk of AD: the Baltimore Longitudinal Study of Aging

OBJECTIVE

To investigate the association between use of calcium channel blockers (CCB), dihydropyridine (DHP) or nondihydropyridine (nonDHP) type CCB and risk of developing Alzheimer's Disease (AD) or mortality. There is evidence suggesting that calcium plays a key role in changes in the brain leading to AD. Previous reports suggest a possible role for CCB in the treatment of AD. However, there are some indications that CCB increase mortality in patients with cardiac disease.

METHODS

Subjects were 1092 participants in the Baltimore Longitudinal Study of Aging (BLSA) older than 60 years of age. Data on CCB use was collected prospectively for up to 19 years. Cox proportional hazards regression was used to estimate relative risks (RR) and confidence intervals (CI) of AD and mortality associated with use of CCB or use of only DHP or nonDHP-CCB. Analyses were adjusted for gender, education, smoking, blood pressure and history of heart problems.

RESULTS

Use of DHP-CCB was not associated with a significantly reduced risk of AD compared to non-users, although the estimate of the RR was low with DHP-CCB (RR = 0.30, 95% CI = 0.07-1.25, P = 0.10). Use of nonDHP-CCB was not associated with reduced risk of AD and the estimate of the RR risk was close to one (RR = 0.82, 95% CI = 0.37-1.83, P = 0.63). In addition, there was no increase in mortality among users of DHP-CCB (RR = 0.64, 95% CI = 0.32-1.29, P = 0.21) or nonDHP-CCB (RR = 1.10, 95% CI = 0.65-1.87, P = 0.72).

CONCLUSION

Users of DHP-CCB and nonDHP-CCB in this study did not have a significantly reduced risk of AD.

Depression and the Risk of Alzheimer Disease

BACKGROUND

Several epidemiologic studies have examined depression as a risk factor for Alzheimer disease with conflicting results. Most studies relied on self-reported depression, but the agreement between self-reported depression and clinical diagnosis has been reported to be weak, thereby diluting the association.

METHODS

A population-based cohort in Odense, Denmark, of 3346 persons age 65-84 years was examined at baseline (1992-1994) and after 2 years (1994-1996) and 5 years (1997-1999). History of depression was collected at baseline as self-report. We used logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Persons with a history of depression had an increased risk of Alzheimer disease both at baseline (OR = 1.7; CI = 1.0-2.7) and at follow up (at 2 years, 1.9 [1.0-3.3] and at 5 years, 1.6 [0.9-2.7]).

CONCLUSIONS

Depression was associated with an increased risk of Alzheimer disease. The odds ratios were lower than generally reported from follow-up studies and are similar to cross-sectional studies.

Diabetes and brain aging: epidemiologic evidence

Increasingly, data from epidemiologic studies suggest diabetes is a risk factor in old age for brain aging, including cognitive impairment and dementia. These associations may reflect a direct effect on the brain of hyperglycemia, or the effects of the diabetes-associated comorbidities of hypertension, dyslipidemia, or hyperinsulinemia. Epidemiologic data on diabetes and brain aging are reviewed. A brief overview is also given of the physiologic mechanisms supporting the epidemiologic data.

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.

Possible association of mitochondrial transcription factor A (TFAM) genotype with sporadic Alzheimer disease

Mitochondrial transcription factor A (TFAM) is essential for transcription and replication of mammalian mitochondrial DNA (mtDNA). Disturbance of maintenance of mtDNA integrity or mitochondrial function may underlay neurodegenerative disorders such as Alzheimer disease (AD). TFAM, the gene encoding TFAM maps to chromosome 10q21.1, a region that showed linkage to late-onset AD in several study samples. We screened TFAM for single nucleotide polymorphisms (SNPs) and genotyped the G>C SNP rs1937, coding for S12T in mitochondrial signal sequence of TFAM, and the A>G SNP rs2306604 (IVS4+113A>G) in 372 AD patients and 295 nondemented control subjects. There was an association of genotype rs1937G/G with AD in females and an association of a TFAM haplotype with AD both in the whole sample and in females. The findings suggest that a TFAM haplotype containing rs1937 G (for S12) may be a moderate risk factor for AD.

Cognitive reserve: implications for diagnosis and prevention of Alzheimer's disease

Epidemiologic evidence suggests that higher occupational attainment and education, as well as increased participation in intellectual, social, and physical aspects of daily life, are associated with slower cognitive decline in healthy elderly and may reduce the risk of incident Alzheimer's disease (AD). There is also evidence from structural and functional imaging studies that patients with such life experiences can tolerate more AD pathology before showing signs of clinical dementia. It has been hypothesized that such aspects of life experience may result in functionally more efficient cognitive networks and, therefore, provide a cognitive reserve that delays the onset of clinical manifestations of dementia. In this article, we review some of the relevant literature of the noted associations between markers of cognitive reserve and AD and discuss the possible mechanisms that may explain these associations.

Dementia / Alzheimer's Disease

Health Issues

Dementia, including Alzheimer's disease (AD) increases exponentially with age from the age of 65. The number of people with dementia will increase significantly over the next three decades as the population ages. While prevalence and incidence rates do not differ markedly in women, compared to men, women live longer on average, so the number of women with dementia is greater than for men. Also, women are more frequently caregivers for people with dementia. Thus, dementia is an important health problem for women.

Key Findings

The Canadian Study of Health and Aging showed an increase in prevalence of dementia with age for both sexes, approximately doubling every five years of age. Rates of AD were higher in women whereas rates of vascular dementia were higher in men. The risk of AD increased with increasing age, lower education, and apolipoprotein E ε4. Regular physical activity was clearly protective in women; this was less clear for men. Use of non-steroidal anti-inflammatory drugs, wine consumption, and past exposure to vaccines decreased the risk of AD. Estrogen replacement therapy did not reduce the risk of AD. About three quarters of caregivers for dementia patients were women.

Data Gaps and Recommendations

The protective effect of regular physical activity for AD provides an additional reason to promote regular physical activity at all ages. Ongoing surveillance of the incidence, prevalence and risks for dementia is needed to monitor the impact of treatments as well as the aging of the population on the burden of dementia.

Can dementia be prevented? Brain aging in a population-based context

As a consequence of global aging of the human population, the occurrence of cognitive impairment and dementia is rapidly becoming a significant burden for medical care and public health systems. By the year 2020, the WHO predicts there will be nearly 29 million demented people in both developed and developing countries. Primary and secondary prevention of dementia through individual and population-level interventions could reduce this imminent risk. Vascular risk factors such as type 2 diabetes, hypertension, dietary fat intake, high cholesterol, and obesity have emerged as important influences on the risk of both vascular and Alzheimer's dementia. Understanding the reasons for differences between populations in genetic vulnerability and environmental exposures may help to identify modifiable risk factors that may lead to effective prevention of vascular and Alzheimer's dementia.

A 2-year follow-up study of cigarette smoking and risk of dementia

The report focused on investigating the relationship between cigarette smoking and dementia in elderly people through prospective studies. We did a 2-year follow-up study of elderly people. A total of 2820 participants aged 60 years old and over from six communities of Chongqing agreed to take part. Dementia was diagnosed with MMSE (Mini-Mental State Examination) and DSM-III-R (Diagnostic and Statistical Manual of Mental Disorders). Participants were classified as never smokers, past smokers, and current smokers. During follow-up, we recorded incident cases of dementia. The association of smoking and dementia was investigated using proportional hazards regression analysis. A total of 121 incident cases of dementia were detected, of which 84 (69%) were Alzheimer's disease, 17 (14%) were vascular dementia, and 21(17%) were other dementia. Compared with never smokers, current smokers had an increased risk of Alzheimer's disease (RR = 2.72; 95% CI = 1.63-5.42) and vascular dementia (RR = 1.98; 95% CI = 1.53-3.12) adjusting for age, sex, education, blood pressure, and alcohol intake. Compared with light smokers, the adjusted risk of Alzheimer's disease was significantly increased among smokers with a medium level of exposure (RR = 2.56; 95% CI = 1.65-5.52), with an even higher risk of Alzheimer's disease in the heavy smoking group (RR = 3.03; 95% CI = 1.25-4.02). Smoking was associated with the risk of dementia. This study suggests that both smoking status and amount is associated with dementia.

How heritable is Alzheimer's disease late in life? Findings from Swedish twins

Although genetic effects are known to be important for early onset Alzheimer's disease, little is known about the importance of genetic effects for late-onset disease. Furthermore, previous studies are based on prevalent cases. Our purpose was to characterize the relative importance of genetic and environmental factors for incident Alzheimer's disease late in life, and to test for differences in the importance of genetic effects at different ages. A cohort of 662 pairs of Swedish twins 52 to 98 years of age who were without symptoms of dementia was followed up for an average of 5 years. Incident dementia cases were detected through follow-up at 2 to 3-year intervals using either cognitive testing or telephone screening followed by dementia workups. A physician, psychologist, and nurse gave consensus diagnoses. During the follow-up period, 5.8% of the sample was diagnosed with Alzheimer's disease. Average age of onset was 83.9 years (standard deviation, 6.3). Of the 26 monozygotic pairs in which at least one twin developed Alzheimer's disease, 5 were concordant (probandwise concordance, 32.2%). The concordance rate for dizygotic pairs was 8.7% (2 of 44 pairs). Structural model fitting indicated that 48% of the variation in liability to Alzheimer's disease could be attributed to genetic variation. Estimates did not differ significantly between twins younger than age 80 years and those older than age 80 years at baseline. Although these genetic estimates for incident disease are lower than those for prevalent disease, the importance of genetic factors for liability to Alzheimer's disease is considerable even late in life.

Alcohol and tobacco consumption as risk factors of dementia: a review of epidemiological studies

The association between dementia and smoking or alcohol use has been examined in several epidemiological studies. In many case-control studies, a decreased risk of dementia or Alzheimer's disease (AD) was observed among smokers. However, when this association was analysed in prospective studies, an increased risk of AD was observed. In addition, in the PAQUID study, we showed that the decreased risk disappeared after adjustment for educational level and occupation. These factors are strong confounders in the association between dementia and tobacco use. We also showed that moderate consumption of wine was associated with a lower risk of developing AD. This result remains unchanged after adjustment for many potential confounders. The association between moderate alcohol consumption and risk of developing a dementia or AD was recently confirmed by prospective studies. In some studies, wine consumption was more specifically associated with a decreased risk, whereas beer or spirit consumption was not associated. These results suggest that tobacco consumption is not associated with a lower risk of dementia and that moderate alcohol intake does not increase the risk of developing dementia.

Alzheimer’s Disease and Vascular Dementia

This chapter explores the frequency with which dementing illnesses occur in populations, their distributions by personal characteristics, and what is known about their causes and potential protective factors. The primary focus is on the most common forms of dementia: Alzheimer's disease and vascular dementia. The chapter summarizes clinical and pathologic features of Alzheimer's disease and vascular dementia, and highlights recent theories of how risk factors affect brain reserve. With the evolution of the epidemiology of dementia from case-control studies to prospective cohort studies has come a new set of methodological challenges. These include identification of representative populations, enhancing subject participation and retention in studies, the need to include institutionalized as well as community-dwelling populations, the non-standardized use of cognitive tests to screen for dementia, and the complexities of the diagnostic process itself. Finally, the chapter summarizes risk and protective factors for disease expression, including cardiovascular risk factors, lifestyle factors, and factors that affect brain reserve.

Tau immunohistochemistry in acute brain injury

Epidemiological studies have identified a history of head injury as a risk factor for Alzheimer's disease. However, the neuropathological mechanism underlying this relationship is as yet unclear. Neuronal cytoskeletal changes in the form of neurofibrillary tangles and neuropil threads have recently been demonstrated in young men who had sustained repetitive head injury and subsequently died in their 20s. In addition, recent experimental studies have found accumulation of tau within neuronal somata and damaged axons following diffuse brain injury. We hypothesized that tau-immunoreactive tangles may be present in the brains of patients who died after a single acute blunt head injury. A total of 45 cases of fatal head injury were immunostained for tau. They comprised nine groups (n=5 for each group) separated by age (0-19 years, 20-50 years, 50+ years) and survival time (<24 h, 24 h-1 week, 1 week-1 month) and were compared with age-matched controls. Subtle alterations in tau immunoreactivity, for example, in oligodendrocytes, were present in some head injury cases but not controls. However, neurofibrillary tangles did not appear more prevalent after traumatic brain injury (TBI) when compared with age-matched controls. Although alterations in tau immunoreactivity may occur which warrant further study, neurofibrillary tangles were not more prevalent after a single fatal episode of TBI.

Regional cerebral blood flow in Parkinson's disease with and without dementia

Tc99 HMPAO SPECT and T1 weighted 3D MRI scans were acquired in cognitively intact subjects with Parkinson's disease (PD) (n = 31), and in PD subjects with dementia (PDD) (n = 34), healthy controls (n = 37), those with Alzheimer's disease (AD) (n = 32), and those with dementia with Lewy bodies (DLB) (n = 15). We used SPM99 to look for regions which showed a reduction in perfusion on SPECT not related to associated structural brain changes assessed by a MRI scan. The precuneus and inferior lateral parietal regions showed a perfusion deficit in Parkinson's disease with dementia, similar to the pattern observed in DLB. In comparison, AD showed a perfusion deficit in the midline parietal region, in a more anterior and inferior location than in PDD, involving the posterior cingulate as well as the precuneus. The perfusion deficits in PDD are similar those in DLB, and in a location associated with visual processing, and may be associated with the visuospatial perception deficits which are present in persons with DLB and PDD.

Update on epidemiological aspects of progressive supranuclear palsy

The cause of progressive supranuclear palsy (PSP), the most common form of the atypical parkinsonian disorders, is unknown. PSP is characterized by four-repeat tau aggregates in neurons (neurofibrillary tangles) and glia in specific basal ganglia and brainstem areas. A thorough literature review led us to hypothesize that genetic and/or environmental factors contribute to its development. It is likely that inheritance of the H1/H1 tau genotype represents a predisposition to develop PSP requiring other environmental or genetic factors. Less likely, a relatively rare mutation with low penetrance could contribute to the abnormal tau aggregation present in this disorder. The possible role of chemicals in the diet or occupation, hypertension, traumatic brain injury, coffee, and inflammation or oxidative injury are reviewed.

Increased neuronal metabolic activity and estrogen receptors in the vertical limb of the diagonal band of Broca in Alzheimer's disease: relation to sex and aging

Changes in the interaction between sex hormones and the cholinergic system are presumed to play a role in cognitive decline in aging and Alzheimer's disease (AD). The hippocampus is one of the most strongly affected brain structures in AD and the vertical limb of the diagonal band of Broca (VDB) is its major source of innervation. In the present study we found, surprisingly, for the first time that the neuronal metabolic activity as measured by the size of the Golgi apparatus in the VDB gradually increases after the age of 50 years in controls and that this process starts earlier and is more pronounced in Alzheimer's disease patients. Neuronal metabolic activity in the VDB was significantly higher in AD than in control patients younger than 70 years of age and was higher in control patients over 70 years than in control patients younger than 70 years of age. The activation of VDB neurons during aging was accompanied by an increased nuclear estrogen receptor (ER) beta staining, which was stronger in patients over 70 years of age than in younger subjects (in both controls and AD patients). Interestingly, as in the nucleus basalis of Meynert, nuclear ERalpha expression was markedly enhanced in AD patients compared to controls independent of age. In addition, evidence was found for the influence of APOE genotype on ERalpha and ERbeta staining in the human VDB in aging and in AD. APOE genotype was positively correlated (epsilon 2 < epsilon 3 < epsilon 4) with the percentage of cytoplasm ERalpha-positive VDB neurons in elderly control male and female subjects and with both nuclear and cytoplasm ERbeta-positive neurons in control women. In conclusion, the VDB is compensatory activated and shows more nuclear ER expression in aging and AD in a sex- and APOE genotype-dependent way. So neither global degeneration or a strongly decreased neuronal metabolism nor a lack of sex hormone receptors in the VDB seems to contribute to the decline in cognition in aging or AD in which the hippocampus plays such a crucial role.

Exploring sex differences in the relationship between depressive symptoms and dementia incidence: prospective results from the PAQUID Study

OBJECTIVES

To estimate the predictive relationship between depressive symptoms and 8-year dementia incidence in a large prospective community sample of French older adults and to compare the effect magnitude for men and women.

DESIGN

Prospective population-based cohort with four interview waves and complete vital status ascertainment.

SETTING

Urban and rural communities in the Aquitaine Region (Gironde and Dordogne), southwest France.

PARTICIPANTS

Three thousand seven hundred seventy-seven adults aged 65 and older residing in noninstitutional settings at study baseline.

MEASUREMENTS

Each participant was interviewed by a neuropsychologist and screened for dementia with the Mini-Mental State Examination, a cognitive test battery, and a standardized questionnaire designed to ascertain the presence of the criteria for dementia according to the Diagnostic and Statistical Manual for Mental Disorders, Third Edition, Revised (DSM-III-R). Dementia status and subtype were confirmed using neurological examination and categorized according to DSM-III-R criteria for dementia and the National Institute of Neurological Disorders and Stroke/Alzheimer's and Related Disorders Association criteria. The Hachinski score was calculated to specify the etiology: possible or probable Alzheimer's disease, vascular dementia, and other types of dementia. Depressive symptomatology was evaluated using the Center for Epidemiologic Studies-Depression scale. Statistical analyses were weighted to correct for attrition not due to mortality.

RESULTS

Ninety-seven men (incidence rate: 14.4/1,000) and 183 women (Incidence rate: 19.0/1,000) developed dementia during 8 years of follow-up. Baseline prevalence of depressive symptomatology was 12.9% for men and 14.7% for women. Depressive symptoms increased risk of dementia at subsequent interview wave, but only for men (odds ratio (OR) (men) = 3.5, 95% confidence interval (CI) = 1.9-6.5; OR (women) = 1.2, 95% CI = 0.7-2.0, P-value for sex difference = 0.03). The hypothesis that vascular depression might explain the observed sex difference was studied, and it was found that risk was 50% higher for men with hypertension who were depressed than for normotensive men. For women, hypertension status did not modify the absence of an association.

CONCLUSION

This study supports the hypothesis of a relationship between proximal depressive symptomatology and dementia in men, but distant depression did not increase dementia risk in this sample. The results suggest that depression in older men might reflect a form of vascular depression associated with cerebral vascular pathology or multiinfarct disease that may amplify the dementing or declining process, hence accelerating the onset of manifest symptoms of dementia.

Prevalence of dementia in a semi-urban population in Sri Lanka: report from a regional survey

BACKGROUND

The prevalence of dementia in Sri Lanka, which has a rapidly ageing population, is unknown.

OBJECTIVE

This study aimed to determine the prevalence of Alzheimer's disease (AD) and other dementias in a semi-urban elderly Sinhala-speaking population in Ragama, Sri Lanka.

METHODS

The study was conducted in two phases. Phase I: After informed consent 703 subjects aged > or =65 years from the study area (population 15 828) were screened for cognitive impairment using the Sinhalese Mini Mental State Examination. Subjects scoring < or =17 were regarded as suspected dementia cases. Phase II: All subjects who screened positive in phase I were included in phase II for detailed evaluation for dementia according DSM IV and NINCDS-ADRDA criteria which included structured neuropsychiatric assessment, laboratory investigations, an axial CT scan of the brain and an informant interview.

RESULTS

In the study sample, 61% were female and 86% were between 65-75 years. 42 subjects screened positive in phase I. Of these, 28 subjects were diagnosed as having dementia, giving an overall prevalence rate of 3.98% (95% Confidence Intervals (CI) =2.6-5.7%). Of these, 20 (71.4%) had probable AD, four had vascular dementia (14.3%), two had mixed (vascular and AD) dementia (7.1%), one had Lewy body dementia, and one had dementia due to syphilis. Greater age, illiteracy and female gender were associated with higher prevalence of dementia.

CONCLUSION

Comparison with other community studies performed in North India suggests that dementia prevalence is higher in Sri Lanka. This may be due to regional differences in disease incidence.

Nonsteroidal anti-inflammatory drug use and the risk for Alzheimer's disease: dissecting the epidemiological evidence

Inflammation is hypothesised to contribute to the genesis of pathology causing or contributing to Alzheimer's disease (AD). As a part of the immune response in the brain, the prostaglandin pathway is induced; this pathway is the target for NSAIDs, the most widely used anti-inflammatory medication. There are many epidemiological studies, which are reviewed here, suggesting NSAIDs reduce the risk for AD. The most recent of these studies suggest NSAIDs should be taken for at least 2 years. There are little data in humans about whether one type of NSAID is more effective than another. To date, randomised, double-blind, clinical trials in patients with AD have been negative. There is one prevention trial that will yield valuable information about the efficacy of NSAIDs in slowing down the progression of, or preventing, AD. At present, no recommendations can be made concerning the when, what, who and for how long a person should take an NSAID to reduce his or her risk for AD.

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.

Mid-life smoking and late-life dementia: the Honolulu-Asia Aging Study

We studied the association between mid-life smoking and late-life dementia in the Honolulu Heart Program (1965-1971) and follow-up assessment for dementia (1991-1996) of 3734 Japanese-American men (80% of survivors). Neuropathologic data were available for 218 men. Adjusting for age, education and apolipoprotein E (APOE) genotype, the risk of Alzheimer's disease (AD) in smokers increased with pack-years of smoking at medium (odds ratio (OR)=2.18, 95% confidence interval (CI)=1.07-4.69) and heavy (OR=2.40; 95% CI=1.16-5.17) smoking levels. Very heavy smoking was not associated with AD (OR=1.08; 95% CI=0.43-2.63). Findings were similar when AD cases included those with cerebrovascular disease and for all dementias combined. Adjustment for cardiovascular and respiratory factors or stratification by apolipoprotein E genotype did not change these associations. In an autopsied subsample, the number of neuritic plaques increased with amount smoked. This study suggests that amount smoked is associated with an increasing risk of AD and Alzheimer-type neuropathology up to heavy smoking levels. The lack of association in very heavy smokers may be due to a hardy survivor effect.

Cigarette smoking and cognitive decline in midlife: evidence from a prospective birth cohort study

OBJECTIVES

The authors investigated the effects of cigarette smoking on midlife cognitive performance.

METHODS

Multiple regression was used to test the association between cigarette smoking and changes in cognitive test scores among male and female members of the British 1946 birth cohort aged between 43 and 53 years.

RESULTS

Smoking was associated with faster declines in verbal memory and with slower visual search speeds. These effects were largely accounted for by individuals who smoked more than 20 cigarettes per day and were independent of sex, socioeconomic status, previous (adolescent) cognitive ability, and a range of health indicators.

CONCLUSIONS

The present results show that heavy smoking is associated with cognitive impairment and decline in midlife. Smokers who survive into later life may be at risk of clinically significant cognitive declines.

Association between dementia and midlife risk factors: the Radiation Effects Research Foundation Adult Health Study

OBJECTIVES

To investigate the association between midlife risk factors and the development of vascular dementia (VaD) or Alzheimer's disease (AD) 25 to 30 years later.

DESIGN

A prevalence study within a longitudinal cohort study.

SETTING

Subjects in the Adult Health Study (a prospective cohort study begun in 1958) have been followed through biennial medical examinations in Hiroshima, Japan.

PARTICIPANTS

One thousand seven hundred seventy-four subjects in Hiroshima, Japan born before September 1932 (1,660 with no dementia, 114 with dementia (51 with AD, and 38 with VaD) diagnosed from 1992 to 1997 according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria).

MEASUREMENTS

The subjects were examined for effect on dementia of sex, age, education, atomic bomb radiation dose, and midlife factors associated with risk (smoking, alcohol intake, physical activity, dietary habits, systolic blood pressure (SBP), body mass index, and history of diabetes mellitus) that had been evaluated in 1965-1970.

RESULTS

VaD prevalence increased significantly with age, higher SBP, and lower milk intake. The odds ratios of VaD for age (in 5-year increments), SBP (10 mmHg increments), and milk intake (almost daily/less than four times a week) were 1.29, 1.33, and 0.35, respectively. The risk factors for VaD were compatible with the risk factors for stroke in this study population. AD prevalence increased significantly with age and lower education. Other midlife factors and radiation dose did not show any significant association with VaD or AD.

CONCLUSION

Increased SBP and low milk intake in midlife were associated with VaD detected 25 to 30 years later. Early behavioral control of the risk factors for vascular disease might reduce the risk of dementia.

Smoking and cognitive performance in the community elderly: a longitudinal study

This prospective study investigated the association between smoking and cognitive performance in a community of nondemented elderly subjects aged 65 or older. All subjects were categorized as current smokers, former smokers, or never smokers. The lifetime cigarette exposure was computed. At baseline, we found the abstainers from smoking had better cognitive performances; however, the differences were not significant after adjusting for age, education, hypertension, diabetes, and vascular events. The lifetime cigarette exposure was not predictive of the cognitive status. At a 3-year follow-up, neither the smoking status nor the lifetime cigarette exposure predicted the declination of cognition.

Bedingungen der Erhaltung und Förderung von Selbst- ständigkeit im höheren Lebensalter (SIMA)

Zusammenfassung: Im Rahmen der 1991 begonnenen Längsschnittstudie SIMA wurde die Entwicklung einer demenziellen Erkrankung unter den Teilnehmern zwischen 1991 und 1998 verfolgt. Für insgesamt 340 der ursprünglich 375 Teilnehmer ließ sich feststellen, ob bei ihnen bis Ende 1998 eine demenzielle Erkrankung aufgetreten ist. Die Teilnehmer lebten bei Studienbeginn selbstständig und waren zwischen 75 und 93 Jahren bzw. im Mittel 79.5 (± 3.5) Jahre alt. Unter Einschluss der inzwischen verstorbenen Teilnehmer erkrankten 46 Teilnehmer an einer Demenz. Weitere 28 Teilnehmer litten an einer leichten kognitiven Beeinträchtigung. In multivariaten Risikoanalysen (Cox Regression) wurden signifikante medizinische und psychologische Risikofaktoren bestätigt, wobei es sich auf der medizinischen Seite jeweils um Diagnosen, auf der psychologischen Seite um Leistungen unter dem Median der Gesamtgruppe handelte. Als die bedeutendsten Demenzrisiken ließen sich verschiedene geringe kognitive Leistungen und das Auftreten einer Frühsymptomatik erkennen. Die Befunde der SIMA-Studie zeigen, dass weder Defizite in einem einzelnen kognitiven Leistungsbereich noch einzelne typische Erkrankungen die ausschließlichen Demenzrisiken im höheren Lebensalter darstellen. Die gleichzeitige Bedeutung insbesondere einer Reihe kognitiver Risikofaktoren dokumentiert zudem, dass der Beginn einer Demenz möglicherweise durch ein multimodales Trainingsprogramm erfolgreich hinausgezögert werden kann.

Prevalence of dementia in older latinos: the influence of type 2 diabetes mellitus, stroke and genetic factors

OBJECTIVES

To estimate dementia prevalence in older Mexican Americans, determine the distribution of dementia by etiology, and evaluate the contribution of type 2 diabetes mellitus, stroke, and apolipoprotein E (ApoE) genotype to dementia.

DESIGN

Analysis of baseline data from an epidemiological cohort study.

SETTING

Sacramento Valley, California.

PARTICIPANTS

One thousand seven hundred eighty-nine Latinos aged 60 and older residing in targeted census tracts during 1998-99.

MEASUREMENTS

Each subject was interviewed and screened for dementia and cardiovascular risk factors and diseases. Fasting blood samples were drawn for glucose, insulin, and lipids. Buccal cells were obtained for genetic analysis of ApoE. A three-stage process of screening was used to diagnose dementia, including cognitive testing, a clinical examination, and imaging to determine etiology. Presence of dementia was established according to National Institute of Neurological Disorders and Stroke/Alzheimers and Related Disorders Association criteria and California Alzheimer's Disease Diagnostic and Treatment Criteria.

RESULTS

Overall dementia prevalence was 4.8%. Prevalence in those aged 85 and older was 31%. Education and Anglo cultural orientation was negatively associated with dementia risk. Risk of dementia was nearly eight times higher in those with both type 2 diabetes mellitus and stroke. Forty-three percent of dementia was attributable to type 2 diabetes mellitus, stroke, or a combination of the two. ApoE allele frequency was E2 5.9%, E3 90.1%, and E4 4%. Those with any E4 and 4-4 combinations had a higher risk for dementia than those with the E3-3 combination.

CONCLUSIONS

Dementia prevalence in this ethnic group is similar to that reported in Canadian and European studies but lower than in Caribbean-Hispanics residing in the United States. The etiological fraction of dementia attributable to type 2 diabetes mellitus and stroke is substantial and points toward the need for intervention research and treatment with the goal of reducing neurological sequelae in groups with high prevalence of type 2 diabetes mellitus. The allele frequency of ApoE was similar to that in other published studies on Mexican Americans. The low frequency of the E4 allele may contribute to the difference in etiology of dementia in older Mexican Americans and older people of European background. Dementia in this ethnic group may be related to preventable causes, with a smaller genetic component than in Europeans.

Research priorities in the evolving demographic landscape of Alzheimer disease and associated dementias

The rapid increase of ethnically diverse late onset dementia-affected persons is bringing a special urgency to Alzheimer disease and associated disorders research. By this decade's end, non-European heritage ethnically diverse persons will account for 25% of the dementia-affected cohort and 33% by mid-century. These populations have received some attention in both dementia-focused basic biomedical and social-behavioral research. However, studies differ greatly with regard to the constructs of culture used, the methodologies used, and representativeness of the populations sampled. Moreover, social status factors are often confounded with cultural variables. Therefore, several clarifying research approaches are suggested. In biomedical research, categorically ascribed (US census type) definitions, or assumed (self-reported) ethnic group designators will not suffice where actual biophysiological sampling precision is needed. A strategy for the phenotypic sampling of cohorts is therefore suggested for this research domain. In social-behavioral research, the acceptance of a common operational definition of culture is urged. And, with reference to a specific social status confound, namely literacy, a neuroimaging research strategy is proposed to determine whether non-literates might not be misclassified relative to the determination of their actual cognitive functioning status. Additionally, two conceptual models for addressing and are briefly presented.

Paraoxonase 1 activity: a new vascular marker of dementia?

Paraoxonase 1 (PON1), an A-esterase with peroxidase-like activity present on the surface of HDL, decreases the peroxidation of LDL. Serum PON1 activity (PON1a) decreases with aging and in disorders associated with a high risk of adverse cardiovascular events (acute myocardial infarction, diabetes mellitus, and chronic renal failure). The implication of vascular factors in Alzheimer-type dementia (ATD) is strongly suspected. We measured PON1a by spectrophotometry using the paraoxon substrate in 180 healthy subjects (controls; mean age: 75.3 +/- 8.9 years; 98 women) and 154 patients admitted for cognitive testing. According to criteria, 45 patients had mild cognitive impairments (MCI; mean age: 75.6 +/- 9.3 years; 28 women), 60 had ATD (mean age: 75.6 +/- 8.3 years; 47 women), and 49 had vascular dementia (VaD; mean age: 77.5 +/- 7.2 years; 33 women). Mean PON1a was lower in VaD (0.25 +/- 0.1 U/mL) than in controls or ATD (both 0.41 +/- 0.2 U/mL, p < 0.01). Mean PON1a values in MCI (0.34 +/- 0.2 U/mL) and ATD (0.41 +/- 0.2 U/mL) were not significantly different. In multiple linear regression, PON1a was negatively correlated with male sex, age, and VaD, and positively correlated with ATD (each correlation p < 0.001). As shown in other high-risk cardiovascular disorders, PON1a seems to be a reliable marker of VaD. Its modification in Alzheimer's disease supports the implication of vascular risk factors in this type of dementia.

Thinking preventively about dementia: a review

BACKGROUND

The dementias of late life now constitute a major public health challenge to our society.

OBJECTIVE

To examine the contributions of neuroscience, clinical treatment and health-care policy to the building of a national programme for preventive approaches to dementia.

METHOD

Critical review of the literature, making use of international databases (Medline, Embase, Psychlit) and British official publications.

RESULTS

Recent developments in a number of research fields afford prospects for advances in primary and secondary prevention. These include findings from case-control and cohort studies of associations with earlier head injury and vascular disease, possibilities of pharmacological protection for persons at high risk for Alzheimer's disease, and the use of more effective anti-dementia drugs in the mild to moderate stages of severity. Research aimed at tertiary prevention is lagging behind, but there are some indications that the worst features of late-stage decline could already be mitigated by improvements in community support services and nursing-home care.

CONCLUSIONS

Containment of the growing social and economic burdens of dementia calls for a national policy to ensure that new research findings can be translated into practice and applied to the benefit of all old people who stand in need. For this purpose the most appropriate conceptual framework is supplied by a preventive model, broadly similar to those already developed for some other forms of chronic degenerative disease.

Early inflammation and dementia: a 25-year follow-up of the Honolulu-Asia Aging Study

Inflammatory responses are associated with cardiovascular disease and may be associated with dementing disease. We evaluated the long-term prospective association between dementia and high-sensitivity C-reactive protein, a nonspecific marker of inflammation. Data are from the cohort of Japanese American men who were seen in the second examination of the Honolulu Heart Program (1968-1970) and subsequently were reexamined 25 years later for dementia in the Honolulu-Asia Aging Study (1991-1996). In a random subsample of 1,050 Honolulu-Asia Aging Study cases and noncases, high-sensitivity C-reactive protein concentrations were measured from serum taken at the second examination; dementia was assessed in a clinical examination that included neuroimaging and neuropsychological testing and was evaluated using international criteria. Compared with men in the lowest quartile (<0.34mg/L) of high-sensitivity C-reactive protein, men in the upper three quartiles had a 3-fold significantly increased risk for all dementias combined, Alzheimer's disease, and vascular dementia. For vascular dementia, the risk increased with increasing quartile. These relations were independent of cardiovascular risk factors and disease. These data support the view that inflammatory markers may reflect not only peripheral disease, but also cerebral disease mechanisms related to dementia, and that these processes are measurable long before clinical symptoms appear.