Metabolic cardiovascular syndrome and risk of dementia in Japanese-American elderly men. The Honolulu-Asia aging study

Metabolic syndrome and Alzheimer's disease: a link to a vascular hypothesis?

Current evidence from epidemiological, neuroimaging, pathological, pharmacotherapeutic, and clinical studies indicate an association of Alzheimer's disease with risk factors of vascular atherosclerotic disease either in isolation or in aggregate. "Metabolic syndrome" (MetS) is the name for a clustering of risk factors for cardiovascular disease and type 2 diabetes that are of metabolic origin. These include central obesity, elevated plasma glucose, high blood pressure, atherogenic dyslipidemia, a prothrombotic state, and a proinflammatory state. In this article, we provide an overview of the relevant literature with regard to the relationship of Alzheimer's disease with MetS. Accumulating evidence suggests a "vascular hypothesis" to be related to the pathology of Alzheimer's disease. In the light of this evidence, clinician may consider lifestyle interventions toward an early and effective cardiovascular risk-factor management to reduce the cardiometabolic and the cognitive decline risk, while further research of other preventive strategies may be warranted.

Vascular risk factors, alcohol intake, and cognitive decline

Since the therapeutic options currently available have demonstrated limited efficacy, the search for preventive strategies for cognitive decline and dementia is mandatory. A possible role of vascular and lifestyle-related factors was recently proposed for age-related changes of cognitive function, predementia syndromes, and cognitive decline of degenerative (Alzheimer's disease, AD) or vascular origin. At present, cumulative evidence suggested that vascular risk factors may be important in the development of mild cognitive impairment (MCI), dementia, and AD. Among vascular-related factors, metabolic syndrome has been associated with the risk of cognitive decline and overall dementia. Moderate alcohol drinking has been proposed as a protective factor against MCI and dementia in several longitudinal studies, but contrasting findings also exist. However, in most cases, these were only observational studies, and results are awaited from large multicenter randomized clinical trials in older persons. At present, vascular risk factor management, lifestyle changes, and drugs could be employed together to delay the onset of dementia syndromes.

Metabolic syndrome and cognitive function in healthy middle-aged and older adults without diabetes

OBJECTIVE

Few studies have addressed whether the metabolic syndrome (MetS) and its individual components are associated with cognitive function in middle-aged and older populations, as well as whether specific areas of cognition are more affected than others. We examined the cross-sectional association between MetS and six areas of cognitive function in healthy cognitively intact adults without diabetes (n = 853, mean age 61 years) randomized in two intervention trials.

METHODS

The National Cholesterol Education Program (NCEP) criteria were used to identify subjects with MetS. Cognitive function was assessed with a neuropsychological battery. A principal components analysis was used to extract five uncorrelated factors interpreted to represent five areas of cognition, and a measure of global cognition was calculated.

RESULTS

MetS was weakly but non-significantly associated with lower verbal learning (beta = -.14 [SE(beta) = 0.09], p = .15). As the number of MetS criteria increased, scores on global cognition (p trend = .01), verbal learning (p trend = .06) and semantic memory (p trend = .04) decreased. Hypertension was the only MetS risk factor that was independently correlated with lower verbal learning (beta = -.17 [SE(beta) = 0.08], p = .04), semantic memory (beta = -.26 [SE(beta) = 0.08], p = .001) and global cognition (beta = -.15 [SE(beta) = 0.07], p = .04).

CONCLUSION

This study adds to the evidence of an association between MetS and lower cognitive function among healthy middle-aged and older adults without CVD and diabetes, as well as confirms the correlation between hypertension and lower cognition.

Obesity and central obesity as risk factors for incident dementia and its subtypes: a systematic review and meta-analysis

While dementia affects 6-10% of persons 65 years or older, industrialized countries have witnessed an alarming rise in obesity. However, obesity's influence on dementia remains poorly understood. We conducted a systematic review and meta-analysis. PUBMED search (1995-2007) resulted in 10 relevant prospective cohort studies of older adults (40-80 years at baseline) with end points being dementia and predictors including adiposity measures, such as body mass index (BMI) and waist circumference (WC). There was a significant U-shaped association between BMI and dementia (P = 0.034), with dementia risk increased for obesity and underweight. Pooled odds ratios (OR) and 95% confidence intervals (CI) for underweight, overweight and obesity compared with normal weight in relation to incident dementia were: 1.36 (1.07, 1.73), 0.88 (0.60, 1.27) and 1.42 (0.93, 2.18) respectively. Pooled ORs and 95% CI for obesity and incident Alzheimer's disease (AD) and vascular dementia were 1.80 (1.00, 3.29) vs. 1.73 (0.47, 6.31) and were stronger in studies with long follow-up (>10 years) and young baseline age (<60 years). Weight gain and high WC or skin-fold thickness increased risks of dementia in all included studies. The meta-analysis shows a moderate association between obesity and the risks for dementia and AD. Future studies are needed to understand optimal weight and biological mechanisms.

Vascular risk factors and dementia in the general population aged >85 years: prospective population-based study

The aim of this study was to evaluate the association between dementia and common vascular risk factors including blood pressure, blood lipids, homocysteine and diabetes mellitus in a population of very old people. This study is a 9-year follow-up prospective population-based study monitoring 339 non-demented subjects aged 85 years or over in the city of Vantaa, Southern Finland. During the follow-up, those individuals with diabetes mellitus at the baseline and new incident stroke had a higher probability for developing dementia. History of hypertension or higher level of education were associated with a lower probability of dementia. It seems that the contribution of vascular risk factors to the risk of dementia may be age-dependent and their role in the very old subjects may be mediated through their influence on cerebrovascular morbidity. Thus, prevention of stroke and diabetes mellitus may reduce the risk of cognitive decline in the very old.

Adiposity, hyperinsulinemia, diabetes and Alzheimer's disease: an epidemiological perspective

The objective of this manuscript is to provide a comprehensive review of the epidemiologic evidence linking the continuum of adiposity, hyperinsulinemia, and diabetes with Alzheimer's disease. The mechanisms for these associations remain to be elucidated, but may include direct actions from insulin, advanced products of glycosilation, cerebrovascular disease, and products of adipose tissue metabolism. Elevated adiposity in middle age is related to a higher risk of Alzheimer's disease. The evidence relating adiposity in old age to Alzheimer's disease is conflicting. Several studies have shown that hyperinsulinemia, a consequence of higher adiposity and insulin resistance, is also related to a higher risk of Alzheimer's disease. Hyperinsulinemia is a risk factor for diabetes, and numerous studies have shown a relation of diabetes with higher Alzheimer's disease risk. Most studies fail the take into account the continuum linking these risk factors which may result in underestimation of their importance in Alzheimer's disease. The implication of these associations is that a large proportion of the world population may be at increased risk of Alzheimer's disease given the trends for increasing prevalence of overweight, obesity, hyperinsulinemia, and diabetes. However, if proven causal, these associations also present a unique opportunity for prevention and treatment of Alzheimer's disease.

Diabetes and other vascular risk factors for dementia: which factor matters most? A systematic review

Vascular risk factors, such as type 2 diabetes, hypertension, obesity and dyslipidaemia often co-occur. Each of these factors has been associated with an increased risk of dementia, but it is uncertain which factor imposes the greatest risk. Moreover, the effect of age at time of exposure may differ across factors. This paper systematically reviews the evidence for the association of each of these risk factors with dementia. Longitudinal population-based studies that assessed the incidence of dementia in relation to diabetes (n=14), hypertension (n=13), dyslipidaemia (n=8) or obesity (n=9) were included. All four risk factors were indeed associated with an increased risk of dementia, but the results of studies on diabetes and obesity were most consistent. The magnitude of the effects was comparable across the risk factors, with odds ratios for 'any dementia' around 1.5. For hypertension, obesity and dyslipidaemia age appeared to modulate the association: the risk of dementia was generally largest in studies that measured the risk factor in midlife (compared to late life) and had a long follow-up time. At midlife, the population attributable risk of dementia was highest for hypertension, up to 30% of cases of late life dementia. Later in life diabetes appears to convey the highest risk of dementia. This review shows that vascular risk factors should be regarded as a major target for preventive measures, but that timing of such measures appears to be critical.

Cholesterol-related genetic risk scores are associated with hypometabolism in Alzheimer's-affected brain regions

We recently implicated a cluster of nine single nucleotide polymorphisms from seven cholesterol-related genes in the risk of Alzheimer's disease (AD) in a European cohort, and we proposed calculating an aggregate cholesterol-related genetic score (CREGS) to characterize a person's risk. In a separate study, we found that apolipoprotein E (APOE) epsilon4 gene dose, an established AD risk factor, was correlated with fluorodeoxyglucose (FDG) positron emission tomography (PET) measurements of hypometabolism in AD-affected brain regions in a cognitively normal American cohort, and we proposed using PET as a presymptomatic endophenotype to help assess putative modifiers of AD risk. Thus, the objective in the present study is to determine whether CREGS is related to PET measurements of hypometabolism in AD-affected brain regions. DNA and PET data from 141 cognitively normal late middle-aged APOE epsilon4 homozygotes, heterozygotes and noncarriers were analyzed to evaluate the relationship between CREGS and regional PET measurements. Cholesterol-related genetic risk scores were associated with hypometabolism in AD-affected brain regions, even when controlling for the effects of APOE epsilon4 gene dose. The results support the role of cholesterol-related genes in the predisposition to AD and support the value of neuroimaging in the presymptomatic assessment of putative modifiers of AD risk.

Vascular risk factors, cognitive decline, and dementia

Dementia is one of the most important neurological disorders in the elderly. Aging is associated with a large increase in the prevalence and incidence of degenerative (Alzheimer's disease) and vascular dementia, leading to a devastating loss of autonomy. In view of the increasing longevity of populations worldwide, prevention of dementia has turned into a major public health challenge. In the past decade, several vascular risk factors have been found to be associated with vascular dementia but also Alzheimer's disease. Some longitudinal studies, have found significant associations between hypertension, diabetus mellitus, and metabolic syndrome, assessed at middle age, and dementia. Studies assessing the link between hypercholesterolemia, atrial fibrillation, smoking, and dementia have given more conflicting results. Furthermore, some studies have highlighted the possible protective effect of antihypertensive therapy on cognition and some trials are evaluating the effects of statins and treatments for insulin resistance. Vascular risk factors and their treatments are a promising avenue of research for prevention of dementia, and further long-term, placebo-controlled, randomized studies, need to be performed.

Association between apolipoprotein E4 and cognitive decline in elderly adults

OBJECTIVE

To determine the influence of apolipoprotein E on cognitive decline in a cohort of elderly men and women.

DESIGN

Prospective study.

SETTING

Scotland, Ireland, and the Netherlands.

PARTICIPANTS

Five thousand eight hundred four subjects aged 70 to 82 from the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER).

MEASUREMENTS

Subjects were assessed at baseline and over a mean 3.2-year (range 0.7-4.2) follow-up for memory (Picture-Word Recall), speed of information processing (Stroop and Letter-Digit Coding), global cognitive function (Mini-Mental State Examination), and activities of daily living.

RESULTS

At baseline, subjects with apolipoprotein E(4) versus those without E(4) had poorer memory performance (mean score difference -0.20 (95% confidence interval (CI)=-0.31 to -0.09) for immediate recall and -0.32 (95% CI=-0.48 to -0.16) for delayed recall and slower information processing (difference in Stroop, 2.79 seconds, (95% CI=1.20-4.28); Letter-Digit score, -0.36, (95% CI=-0.77-0.05). Subjects with apolipoprotein E(4) showed a greater decline in immediate (-0.22, 95% CI=-0.33 to -0.11) and delayed (-0.30, 95% CI=-0.46 to -0.15) memory scores but no significant change in speed of information processing (Stroop, P=.17; Letter-Digit, P=.06). Memory scores decreased 2.5% from baseline in those without E(4), 4.3% in E(4) heterozygotes (P=.01 for immediate and P=.03 for delayed, vs no E(4)) and 8.9% to 13.8% in E(4) homozygotes (P=.04 for immediate and P=.004 for delayed, vs heterozygotes). Apolipoprotein E(4) was associated with greater decline in instrumental activities of daily living (P<.001). Cognitive decline was not associated with lipoprotein levels.

CONCLUSION

Findings in PROSPER indicate that E(4) is associated with more-rapid cognitive decline and may, therefore, predispose to dementia.

Plasma cytokines profile in older subjects with late onset Alzheimer's disease or vascular dementia

Some cytokines have been involved in the pathogenesis of late onset Alzheimer's disease (LOAD). A possible increase in plasma cytokines levels has been reported in LOAD and vascular dementia (VD), but the results of previous studies are conflicting. We evaluated the plasma levels of IL-6, TNF-alpha, IL-1beta, and IL-10 in four groups of older individuals: 60 patients with LOAD, 80 patients with VD, 40 subjects with cerebrovascular disease but without dementia (CDND), and 42 controls (C). By analysis of covariance (adjustment for age, gender, coronary heart disease, diabetes, hypertension, smoking, and alcohol consumption) we found that: *IL-1beta was higher in VD, LOAD, and CDND compared with controls (p<0.005). *TNF-alpha was higher in VD and LOAD compared to C (p<0.05), and in VD compared to LOAD (p<0.03). *IL-6 was higher in VD compared with LOAD (p<0.03). No differences in IL-10 values were found (Kruskal-Wallis, Asymp. Sig. 0.14). By logistic regression analysis, we demonstrated that high levels (defined as above the median) of IL-1beta and TNF-alpha, but not of IL-6, were associated with increased likelihood of having VD and LOAD compared to C, while high IL-6 levels were associated with a increased probability of having VD, compared with LOAD. Our study support the notion of a low-grade systemic inflammation in older patients with LOAD or VD, characterized by an increase in plasma IL-1beta and TNF-alpha levels. The high IL-6 levels found in VD might be not a specific finding, as it might come from several conditions including atherosclerosis and related vascular risk factors, comorbidity, and frailty.

Midlife risk factors for subtypes of dementia: a nested case-control study in Taiwan

OBJECTIVE

To identify the midlife risk factors for subtypes of dementia newly developed later in life.

METHODS

A nested case-control study was conducted on 157 demented cases and 628 comparison cases selected from 40,636 men and women who were enrolled from 1982 to 1992. Four comparison cases were frequency-matched on age, time at enrollment (within 6 months), gender, and residential township. Midlife risk factors included vascular risk factors (body mass index [BMI], total cholesterol, total triglycerides, blood glucose, cerebrovascular accident [CVA] history, diabetes mellitus history, and hypertension history), cigarette smoking, and alcohol consumption. Dementia assessments were ascertained through the computerized data linkage from National Health Insurance Database from 2000 to 2002 and clinically confirmed by neurologists or psychiatrists. Conditional logistic regression analysis was used to estimate the matched odds ratio (OR) and its 95% confidence intervals (CI) for each risk factor.

RESULTS

A J-shaped relationship was observed between BMI (kg/m(2)) and dementia. The multivariate-adjusted ORs (95% CI) of developing dementia were 1.84 (1.02-3.33), 1.87 (1.08-3.23) and 2.44 (1.39-4.28), respectively, for BMIs of <20.5, 23.0-25.4, >or=25.5 compared with a BMI of 20.5-22.9 as the referent group (OR = 1.0). Similar findings were observed for Alzheimer disease (AD) and vascular dementia (VaD). The association between obesity (BMI >or=25.5) and both AD and VaD was statistically significant among cigarette smokers but not among nonsmokers. Additionally, history of CVA was a significant risk factor for VaD, but not for AD.

CONCLUSION

Being underweight, being overweight, and a cerebrovascular accident in midlife may increase the risk of dementia in late life.

The effects of tobacco smoke and nicotine on cognition and the brain

Tobacco smoke consists of thousands of compounds including nicotine. Many constituents have known toxicity to the brain, cardiovascular, and pulmonary systems. Nicotine, on the other hand, by virtue of its short-term actions on the cholinergic system, has positive effects on certain cognitive domains including working memory and executive function and may be, under certain conditions, neuroprotective. In this paper, we review recent literature, laboratory and epidemiologic, that describes the components of mainstream and sidestream tobacco smoke, including heavy metals and their toxicity, the effect of medicinal nicotine on the brain, and studies of the relationship between smoking and (1) preclinical brain changes including silent brain infarcts; white matter hyperintensities, and atrophy; (2) single measures of cognition; (3) cognitive decline over repeated measures; and (4) dementia. In most studies, exposure to smoke is associated with increased risk for negative preclinical and cognitive outcomes in younger people as well as in older adults. Potential mechanisms for smoke's harmful effects include oxidative stress, inflammation, and atherosclerotic processes. Recent evidence implicates medicinal nicotine as potentially harmful to both neurodevelopment in children and to catalyzing processes underlying neuropathology in Alzheimer's Disease. The reviewed evidence suggests caution with the use of medicinal nicotine in pregnant mothers and older adults at risk for certain neurological disease. Directions for future research in this area include the assessment of comorbidities (alcohol consumption, depression) that could confound the association between smoking and neurocognitive outcomes, the use of more specific measures of smoking behavior and cognition, the use of biomarkers to index exposure to smoke, and the assessment of cognition-related genotypes to better understand the role of interactions between smoking/nicotine and variation in genotype in determining susceptibility to the neurotoxic effects of smoking and the putative beneficial effects of medicinal nicotine.

Brain white matter expansion in human obesity and the recovering effect of dieting

CONTEXT AND OBJECTIVE

Obesity is associated with several metabolic abnormalities. Recent studies suggest that obesity also affects brain function and is a risk factor for some degenerative brain diseases. The objective of this study was to examine the effects of weight gain and weight loss on brain gray and white matter structure. We hypothesized that possible differences seen in the brains of obese subjects would disappear or diminish after an intensive dieting period.

METHODS

In part I of the study, we scanned with magnetic resonance imaging 16 lean (mean body mass index, 22 kg/m(2)) and 30 obese (mean body mass index, 33 kg/m(2)) healthy subjects. In part II, 16 obese subjects continued with a very low-calorie diet for 6 wk, after which they were scanned again. Regional brain white and gray matter volumes were calculated using voxel-based morphometry.

RESULTS

White matter volumes were greater in obese subjects, compared with lean subjects in several basal brain regions, and obese individuals showed a positive correlation between white matter volume in basal brain structures and waist to hip ratio. The detected white matter expansion was partially reversed by dieting. Regional gray matter volumes did not differ significantly in obese and lean subjects, and dieting did not affect gray matter.

CONCLUSIONS

The precise mechanism for the discovered white matter changes remains unclear, but the present study demonstrates that obesity and dieting are associated with opposite changes in brain structure. It is not excluded that white matter expansion in obesity has a role in the neuropathogenesis of degenerative brain diseases.

Metabolic syndrome and dementia risk in a multiethnic elderly cohort

BACKGROUND/AIMS

The metabolic syndrome (MeSy) may be related to Alzheimer's disease (AD). Our aims were to investigate the association of the MeSy with incident dementia in a multiethnic elderly cohort in the United States.

METHODS

We conducted cross-sectional and prospective analyses in 2,476 men and women aged 65 years and older and with data available on the MeSy and dementia diagnosis in Northern New York City. MeSy was defined by the National Cholesterol Education Program Adult Treatment Program III and the European Group for the Study of Insulin Resistance criteria. Dementia was diagnosed using standard criteria.

RESULTS

No association was found between MeSy and prevalent dementia. After 4.4 years of follow-up, 236 individuals of the 1,833 without prevalent dementia developed dementia. MeSy was not associated with incident dementia. Of the components of the MeSy, diabetes and hyperinsulinemia were associated with an increased risk of incident AD [hazard ratio 1.4 (95% CI 1.0-2.1), and hazard ratio 1.4 (95% CI 0.9-2.7), respectively] and dementia associated with stroke [hazard ratio 1.9 (95% CI 1.1-3.1), and hazard ratio 2.3 (95% CI 1.1-4.7), respectively].

CONCLUSIONS

The MeSy was not associated with an increased dementia risk in a multiethnic elderly cohort, but diabetes and hyperinsulinemia were. In the elderly, examining diabetes and hyperinsulinemia separately may be preferable to using the MeSy as a risk factor.

Non-pharmacologic prevention of Alzheimer's disease: nutritional and life-style risk factors

We conducted a review of cohort studies and interventional studies on nutritional and life-style risk factors and primary prevention of Alzheimer's Disease. Studies were assessed by the Oxford classification. Interventional studies exist for mental training and vitamin supplementation. For alcohol, fat and fish intake, mediterranean diet, homocysteine, overweight/caloric intake, physical and social activity, hypercholesterolemia, diabetes and smoking, currently there is only evidence from cohort studies. Cognitive stimulation by mental training increases mental functions and can be recommended on the basis of positive interventional studies. Vitamin supplementation cannot prevent AD on the basis of interventional studies. Hyperlipidemia, hyperhomocysteinemia, diabetes and typical life-style factors (alcohol, smoking, obesity etc.) modestly increased AD risk, fish, mediterranean diet and unsaturated fat or n-3 fatty acids and social activity are protective in observational cohorts, but interventional studies are lacking.

Cognition and dementia in Type 2 diabetes: brain imaging correlates and metabolic and vascular risk factors

This review addresses the impact of Type 2 diabetes mellitus on the brain. We show that there is convincing evidence that Type 2 diabetes mellitus is associated with accelerated cognitive decline and dementia. The structural basis for these cognitive deficits includes both vascular lesions and global cerebral atrophy. Cerebral changes may already develop in prediabetes mellitus stages. Several areas of uncertainty need to be resolved in order to develop effective preventive strategies. Information on the risk factors for accelerated cognitive decline in patients with Type 2 diabetes mellitus is still scarce. Identification of these factors might help to identify individuals who are at risk for clinically relevant impairments and to develop specific interventions. Further studies on the course of development of cognitive decline in Type 2 diabetes mellitus may help to decide at what stage these interventions should be initiated.

Invited commentary: lipoproteins and dementia - is it the apolipoprotein A-I?

Because of the aging of the population, dementia has become a major public health problem. There has been growing evidence for a possible association between lipids and dementia. A large body of literature has demonstrated multiple hypothesized biologic links between lipids and neurodegenerative or other biologic pathways connected to dementing processes. However, the epidemiologic associations have been conflicting: dyslipidemia at middle age, but not in later life, seems to be associated with higher dementia risk in some but not all studies. Results from the Honolulu-Asia Aging Study reported by Saczynski et al. (Am J Epidemiol 2007;165:985-92) suggest that lipoprotein constituents, such as apolipoprotein A-I, a major component of the high density lipoprotein, may be more informative in enlightening the association between lipids and dementia. In this commentary, the epidemiology and biology of apolipoprotein A-I in relation to dementia is reviewed.

Measures of adiposity and dementia risk in elderly persons

BACKGROUND

Studies relating adiposity to dementia are conflicting. We explored the associations of body mass index (BMI), (calculated as weight in kilograms divided by the square of height in meters) waist circumference, and weight change to dementia, probable Alzheimer disease, and dementia associated with stroke (DAS).

DESIGN

Persons without dementia were followed up for 5 years; 893 persons had BMI data, 907 had waist circumference data, and 709 had a second weight measurement. Dementia was ascertained using standard methods. Cox proportional hazards regression was used for analyses using follow-up as time to event, adjusting for demographics and apolipoprotein E-epsilon4 status.

RESULTS

Compared with persons in the first quartile of BMI, persons in the third quartile had a lower dementia and Alzheimer disease risk and persons in the second quartile had a lower DAS risk. The association between BMI and dementia resembled a U shape in those younger than 76 years, while dementia risk decreased with higher BMI in those 76 years and older. The fourth quartile of waist circumference was related to a higher DAS risk in the whole sample, and to dementia and Alzheimer disease in persons younger than 76 years. Weight loss was related to a higher dementia and DAS risk, and weight gain was related to a higher DAS risk only.

CONCLUSIONS

The prospective association between adiposity and dementia differs depending on the anthropometric measure used, and is modified by age. This may explain previous conflicting reports.

Metabolic syndrome and cognitive function: a population-based follow-up study in elderly women

OBJECTIVE

To test the hypothesis that metabolic syndrome predicts cognitive impairment, and to examine the association of single metabolic risk factors with cognitive functioning.

METHODS

We performed a 12-year follow-up study in a population-based sample of 101 women aged 60-70 years at baseline. Metabolic syndrome was defined by the National Cholesterol Education Program criteria (> or =3 out of 5 risk factors). Global cognitive function was measured by the Mini-Mental State Examination both at baseline and follow-up. A detailed neuropsychological evaluation for memory and cognitive speed was performed at follow-up.

RESULTS

The prevalence of metabolic syndrome increased from 13% at baseline to 49% at follow-up (p < 0.001). Women with metabolic syndrome at baseline had a 4.27 (95% confidence interval: 1.02-17.90; p = 0.047) times higher risk of poor memory at follow-up after adjustment for age, education and depression. The increasing number of metabolic risk factors was associated with worsening of memory at follow-up (p = 0.034 for linear trend). Women with low baseline levels of high-density lipoprotein (HDL) cholesterol were more likely to have poor memory at follow-up than those with higher HDL levels (p = 0.028). The risk of having poor memory increased by 46.5% (95% confidence interval: 15-66%; p = 0.008) with 1 SD decrease in HDL cholesterol level.

CONCLUSION

In elderly women, metabolic syndrome may be an important contributor to worsening of memory, which is an essential part of mild cognitive impairment.

Guarding the blood-brain barrier: a role for estrogen in the etiology of neurodegenerative disease

Although the effect of estrogen replacement therapy on the incidence of the neurodegenerative disease such as Alzheimer's disease is controversial, experimental studies indicate that estrogen replacement to young adult animals is neuroprotective and that perimenopausal estrogen replacement is associated with a decreased incidence of Alzheimer's disease. Estrogen affects a wide variety of cellular processes that can protect neuronal health. This article considers the disruption of the blood-brain barrier in Alzheimer's disease and forwards the hypothesis that estrogen may preserve neural health by maintaining the integrity of the blood-brain barrier.

High impact running improves learning

Regular physical exercise improves cognitive functions and lowers the risk for age-related cognitive decline. Since little is known about the nature and the timing of the underlying mechanisms, we probed whether exercise also has immediate beneficial effects on cognition. Learning performance was assessed directly after high impact anaerobic sprints, low impact aerobic running, or a period of rest in 27 healthy subjects in a randomized cross-over design. Dependent variables comprised learning speed as well as immediate (1 week) and long-term (>8 months) overall success in acquiring a novel vocabulary. Peripheral levels of brain-derived neurotrophic factor (BDNF) and catecholamines (dopamine, epinephrine, norepinephrine) were assessed prior to and after the interventions as well as after learning. We found that vocabulary learning was 20 percent faster after intense physical exercise as compared to the other two conditions. This condition also elicited the strongest increases in BDNF and catecholamine levels. More sustained BDNF levels during learning after intense exercise were related to better short-term learning success, whereas absolute dopamine and epinephrine levels were related to better intermediate (dopamine) and long-term (epinephrine) retentions of the novel vocabulary. Thus, BDNF and two of the catecholamines seem to be mediators by which physical exercise improves learning.

Update on hypertension and Alzheimer's disease

Several studies report that blood pressure is increased in victims of Alzheimer's disease (AD) decades before the onset of the disease. Years before onset of Alzheimer's disease, blood pressure start to decrease and continues to decrease during the disease process. High blood pressure has also been related to pathological manifestations of Alzheimer's disease (senile plaques, neurofibrillary tangles, hippocampal atrophy). The exact mechanism behind these associations is not clear. Hypertension is also a risk factor for stroke, ischemic white matter lesions, silent infarcts, general atherosclerosis, myocardial infarction and cardiovascular diseases, and often clusters with other vascular risk factors, including diabetes mellitus, obesity and hypercholesterolemia. Also these risk factors have been related to Alzheimer's disease. Hypertension may thus cause cerebrovascular disease that may increase the possibility for individuals with AD encephalopathy to express a dementia syndrome. Hypertension may also lead to vessel wall changes in the brain, leading to hypoperfusion, ischemia and hypoxia which may initiate the pathological process of AD. Finally, subclinical AD may lead to increased blood pressure, and similar biological mechanisms may be involved in the pathogenesis of both disorders. Hypertension is a common disorder and often untreated. Several observational studies have reported that use of antihypertensives decreases risk of AD. Even though hypertension only results in a moderately increased risk of AD, or overall dementia, better treatment of hypertension may have an immense effect on the total number of demented individuals.

Cardiac risk factors and potential treatments in Alzheimer's disease

Dementia is one of the commonest neurological disorders in the elderly population. In regards to the increasing longevity of populations worldwide, prevention of dementia has become a major public health challenge. There has been an intense research in the identification of modifiable risk factors for dementia. These risk factors could then be used as targets for intervention, pharmacologic or non-pharmacologic. Numerous reports of the relation between cardiovascular risk factors and cognitive decline and dementia have been published over the past years. This review focuses on the cardiovascular risk factors hypertension, hyperlipidemia and diabetes mellitus as targets for prevention of cognitive decline, overall dementia and Alzheimer's disease. Observational studies and clinical trials regarding the association between antihypertensive, lipid lowering and antidiabetic medications and the risk of impaired cognition, dementia or Alzheimer's disease are reviewed. Based on these data, we propose that early interventions at reducing these cardiovascular risk factors may have an impact on future incidence and prevalence of cognitive deficits of many etiologies including Alzheimer's disease.

Hematologic risk factors of vascular disease and their relation to dementia

Multiple studies have implicated vascular-related conditions as risk factors for dementia. Clarification of these factors in dementia is important because most are modifiable, and may serve as the basis for preventive strategies. Several hematologic factors are associated with vascular diseases, but their relation to dementia is unclear. This review examines biological and epidemiological evidence concerning the role of these hematologic factors in dementia, and dementia subtypes. Reviewed factors include homocysteine, cholesterol, fatty acids, antioxidants, and C-reactive protein. The vast majority of studies reviewed are cross-sectional. Longitudinal studies with serial hematologic measures are needed to clarify the relationship between these factors and dementia over the lifespan. A necessary step is to examine multiple hematologic factors simultaneously, rather than in isolation, to determine how these factors are interrelated.

Cholesterol as a risk factor for Alzheimer's disease - epidemiological evidence

Although dementia is usually a late-life syndrome, it is now well known that pathological changes begin quite early in adulthood, outside the classical age borders of geriatric specialties. In order to design effective preventive strategies, adequate information can only be gathered by taking a life-long view of Alzheimer's disease (AD). Dementia risk is the result of exposure to both harmful and protective factors along the life course, and these factors, as well as their impact on the individual's health status, change over time. This review aims at presenting current epidemiological data on serum cholesterol levels and dietary fat intake as risk factors for dementia/AD, and at discussing the reasons and significance of contradictions between various studies. Reducing dementia risk may be possible by influencing the serum lipid profile. A more detailed characterization of the mechanisms behind the association of cholesterol (in both serum and brain) with dementia/AD, mechanisms about which little is currently known, would allow a better translation of research findings into clinical practice.

Cognitive impairment and frontal-subcortical geriatric syndrome are associated with metabolic syndrome in a stroke-free population

BACKGROUND

Metabolic syndrome (Met.S) consists of a conglomeration of obesity, hypertension, glucose intolerance, and dislipidemia. Frontal-subcortical geriatric syndrome (FSCS) is caused by ischemic disruption of the frontal-subcortical network. It is unknown if Met.S is associated with FSCS.

METHODS

We evaluated 422 community-dwelling elderly (> or =60) in Brazil. FSCS was defined as the presence of at least one frontal release sign (grasping, palmomental, snout, or glabellar) plus coexistence of > or =3 the following criteria: (1) cognitive impairment, (2) late-onset depression, (3) neuromotor dysfunction, and (4) urgency incontinence. All values were adjusted to age and gender.

RESULTS

Met.S was present in 39.3% of all subjects. Cases without any of the FSCS components represented 37.2% ('successful neuroaging' group). People with 1-3 of the FSCS components ('borderline pathological neuroaging' group) were majority (52.6%), whereas those with 4-5 of these components (FSCS group) were minority (10.2%). Met.S was significantly associated with FSCS (OR=5.9; CI: 1.5-23.4) and cognitive impairment (OR=2.2; CI: 1.1-4.6) among stroke-free subjects. Number of Met.S components explained 30.7% of the variance on the number of FSCS criteria (P<0.001). If Met.S were theoretically removed from this population, prevalence of FSCS would decline by 31.6% and that of cognitive impairment by 21.4%.

CONCLUSIONS

Met.S was significantly associated with a 5.9 and 2.2 times higher chance of FSCS and cognitive impairment, respectively. Met.S might be a major determinant of 'successful' or 'pathological' neuroaging in western societies.

Cardiovascular disease and Alzheimer's disease: common links

Growing evidence supports a strong and likely causal association between cardiovascular disease (CVD), and its risk factors, with incidence of cognitive decline and Alzheimer's disease. Individuals with subclinical CVD are at higher risk for dementia and Alzheimer's. Several cardiovascular risk factors are also risk factors for dementia, including hypertension, high LDL cholesterol, low HDL cholesterol and especially diabetes. Moderate alcohol appears to be protective for both CVD and dementia. In contrast, inflammatory markers predict cardiovascular risk, but not dementia, despite biological plausibility for such a link. The substantial overlap in risk factors points to new avenues for research and prevention.

Risk score for the prediction of dementia risk in 20 years among middle aged people: a longitudinal, population-based study

BACKGROUND

Several vascular risk factors are associated with dementia. We sought to develop a simple method for the prediction of the risk of late-life dementia in people of middle age on the basis of their risk profiles.

METHODS

Data were used from the population-based CAIDE study, which included 1409 individuals who were studied in midlife and re-examined 20 years later for signs of dementia. Several midlife vascular risk factors were studied to create the scoring tool. The score values were estimated on the basis of beta coefficients and the dementia risk score was the sum of these individual scores (range 0-15).

FINDINGS

Occurrence of dementia during the 20 years of follow-up was 4%. Future dementia was significantly predicted by high age (> or = 47 years), low education (< 10 years), hypertension, hypercholesterolaemia, and obesity. The dementia risk score predicted dementia well (area under curve 0.77; 95% CI 0.71-0.83). The risk of dementia according to the categories of the dementia risk score was 1.0% for those with a score of 0-5, 1.9% for a score of 6-7, 4.2% for a score of 8-9, 7.4% for a score of 10-11, and 16.4% for a score of 12-15. When the cut-off of 9 points or more was applied the sensitivity was 0.77, the specificity was 0.63, and the negative predictive value was 0.98.

INTERPRETATION

The dementia risk score is a novel approach for the prediction of dementia risk, but should be validated and further improved to increase its predictive value. This approach highlights the role of vascular factors in the development of dementia and could help to identify individuals who might benefit from intensive lifestyle consultations and pharmacological interventions.

Adiposity indices and dementia

Indicators of adiposity, such as body-mass index (BMI), may be markers for changes in energy metabolism that influence dementia risk, progression, and ultimately death. Cross-sectional studies show that people with dementia have a lower BMI than those without dementia, which is potentially due to a greater rate of BMI decline occurring during the years immediately preceding dementia onset. However, a high BMI can also increase the risk for dementia when measured before clinical dementia onset, which might be due to vascular disorders or bioactive hormonal compounds that are secreted by adipose tissue. In this personal view, I consider how dementia is associated with BMI by looking at the role of BMI and obesity syndromes, mechanisms associated with adiposity, and the potential for hypothalamic dysregulation during the life course. Understanding the life course of adiposity by use of common surrogate measures, such as BMI, among those who do and do not develop dementia is relevant for understanding the causes of dementia and for shaping possible treatment options.

Lipids and the pathogenesis of Alzheimer's disease: is there a link?

Alzheimer's disease (AD) is a heterogeneous neurodegenerative disorder characterized pathologically by amyloid-beta plaques, neurofibrillary tangles and neuronal loss. Its fundamental cause(s) and the pathological cascades leading to clinical symptoms remain unknown. Lipids and lipid peroxidation products have important roles in the homeostasis of the central nervous system. As well, lipid transport genes and vascular changes associated with peripheral dyslipidemia have been associated with an increased risk of AD. The present review discusses ways in which lipids may be involved in the pathogenesis of AD-associated neurodegeneration through their roles as neuronal structural components, cell modulators, or second messengers. Given the many possibilities through which lipids may be directly involved in or contribute to the pathogenesis of AD, the use of lipids as biomarkers for disease progression is discussed, as are other avenues for future research.

Risk of dementia in diabetes mellitus: a systematic review

The relation between diabetes and major types of dementia is controversial. This systematic review examines the incidence of dementia in people with diabetes mellitus. We identified 14 eligible longitudinal population-based studies of variable methodological quality. The incidence of "any dementia" was higher in individuals with diabetes than in those without diabetes in seven of ten studies reporting this aggregate outcome. This high risk included both Alzheimer's disease and vascular dementia (eight of 13 studies and six of nine studies respectively). Detailed data on modulating and mediating effects of glycaemic control, microvascular complications, and comorbidity (eg, hypertension and stroke) were generally absent. The findings of mechanistic studies suggest that vascular disease and alterations in glucose, insulin, and amyloid metabolism underlie the pathophysiology, but which of these mechanisms are clinically relevant is unclear. Further high quality studies need to be initiated, with objective diabetes assessment, together with reliable methods to establish the contribution of vascular disease and other comorbidity to dementia.

Cholesterol and Alzheimer's disease—is there a relation?

The predominating theory on the pathophysiology of Alzheimer's disease (AD) concerns the mis-metabolism of amyloid precursor protein (APP). As a result of this mis-metabolism, there is an increased production of the 42 amino acid form of beta-amyloid (Abeta42) that rapidly will form oligomers that initiates a cascade of events leading to the accumulation of amyloid plaques. Commonly recognised as vascular factors, hypertension, hypercholesterolemia and diabetes and the inheritance of the epsilon4 allele of the APOE gene, are also risk factors for AD. These risks have been found to promote the production of Abeta42. An association between cholesterol and the development of AD was suggested in the early 1990s and ever since, an increasing amount of research has confirmed that there is a link between cholesterol and the development of AD. A high cholesterol levels in mid-life is a risk for AD and statins, i.e., cholesterol-lowering drugs, reduce this risk. Statins may not only inhibit enzymes involved in the endogenous synthesis of cholesterol but also affect enzymes involved in Abeta metabolism, i.e., alpha-secretase and beta-secretase. This normalises the breakdown of APP thereby promoting the non-amyloidogenic pathway. In this review, investigations focusing on cholesterol and Alzheimer's disease are presented.

Lipid metabolism in cognitive decline and dementia

This review will focus on the current knowledge on circulating serum and plasma risk factors of cognitive decline of degenerative (Alzheimer's disease, AD) or vascular origin (vascular dementia, VaD) linked to cholesterol homeostasis and lipoprotein disturbances, i.e. total cholesterol (TC), 24S-hydroxy-cholesterol, lipoprotein(a) (Lp(a)), or apolipoprotein E (APOE). These measures linked to lipoprotein metabolism appear to be altered in AD, VaD, or predementia syndrome relative to controls, but with contrasting results. At present, several studies have demonstrated the dependence of APOE serum levels upon the APOE genotype, nonetheless serum APOE levels seems not to be a credible risk factor or a biochemical marker for AD instead of APOE genotyping. In fact, there was no consistent association of serum or plasma apoE protein levels with the disease when controlled for APOE genotype. In addition, there are some evidence that higher Lp(a) levels could be linked with AD, although there are studies suggesting an increased presence of low molecular weight apo(a) in AD, VaD, and frontotemporal dementia, that are associated with elevated Lp(a) levels. In fact, the apo(a) gene is highly polymorphic in length due to variation in the numbers of a sequence encoding the apo(a) kringle 4 domain, and plasma levels of Lp(a) are inversely correlated with apo(a) size. Furthermore, although serum/plasma levels of TC and 24S-hydroxycholesterol are not credible diagnostic markers for AD and cognitive decline, the current evidence suggests that they may be modifiable risk/protective factors. The prevailing wisdom is that high TC is a risk factor for dementia. However, the relationship between TC and dementia may vary considerably depending on when cholesterol is measured over the life course or, alternatively, in relation to the underlying course of the disease. Several observational studies have suggested that statins, which are effective in lowering cholesterol, may reduce the risk of dementia, but the results of these reports are inconclusive. Thus, more studies with long-term follow-up and serial assessments of TC are needed to further clarify the causal relationship between cholesterol and dementia.

Population-based neuropathological studies of dementia: design, methods and areas of investigation--a systematic review

Background

Prospective population-based neuropathological studies have a special place in dementia research which is under emphasised.

Methods

A systematic review of the methods of population-based neuropathological studies of dementia was carried out. These studies were assessed in relation to their representativeness of underlying populations and the clinical, neuropsychological and neuropathological approaches adopted.

Results

Six studies were found to be true population-based neuropathological studies of dementia in the older people: the Hisayama study (Japan); Vantaa 85+ study (Finland); CC75C study (Cambridge, UK); CFAS (multicentre, UK); Cache County study (Utah, USA); HAAS (Hawaï, USA). These differ in the core characteristics of their populations. The studies used standardised neuropathological methods which facilitate analyses on: clinicopathological associations and confirmation of diagnosis, assessing the validity of hierarchical models of neuropathological lesion burden; investigating the associations between neuropathological burden and risk factors including genetic factors. Examples of findings are given although there is too little overlap in the areas investigated amongst these studies to form the basis of a systematic review of the results.

Conclusion

Clinicopathological studies based on true population samples can provide unique insights in dementia. Individually they are limited in power and scope; together they represent a powerful source to translate findings from laboratory to populations.

Vascular dementia prevention: a risk factor analysis

Brain injury from ischemic or hemorrhagic cerebrovascular disease (CVD) produces decline in cognitive functions and vascular dementia (VaD). Likewise, CVD may cause VaD from hypoperfusion of susceptible brain areas. CVD may also worsen degenerative dementias such as Alzheimer's disease. Significant advances have been made in the identification and control of risk factors for stroke and cardiovascular disease. The main risk factors for VaD include age, hypertension and absence of antihypertensive medication, diabetes, cigarette smoking, history of cardiovascular disease (coronary heart disease, congestive heart failure, peripheral vascular disease), atrial fibrillation, left ventricular hypertrophy, hyperhomocysteinemia, orthostatic hypotension, cardiac arrhythmias, hyperfibrinogenemia, and sleep apnea. Recently identified risk factors include chronic infection and elevation of C-reactive protein, particularly in patients with diabetes. Evidence from controlled clinical trials strongly suggests that control of vascular risk factors, in particular hypertension, could prevent the development of dementia.

The impact of diabetes on cognition: What can be learned from rodent models?

Diabetes mellitus is associated with modest impairments in cognition, particularly in the elderly. In addition, the risk of dementia is increased. We review herein studies in rodent models that may help to identify the mechanisms that underlie these adverse effects of diabetes on the brain. Abnormalities in learning and memory, synaptic plasticity, and glutamatergic neurotransmission have now been identified in a number of these models. In general, observations in models characterized by chronic hyperglycaemia and hypoinsulinaemia (referred to as models of type 1 diabetes) are quite consistent, and these models are being increasingly used to study the pathogenesis and to develop new treatments. However, results from models characterized by insulin resistance, hyperinsulinaemia, and modest hyperglycaemia (referred to as models of type 2 diabetes) are much more variable. Moreover, the possible interaction between diabetes and aging has not been examined in sufficient detail. Because clinically relevant cognitive deficits mainly occur in elderly patients with type 2 diabetes, the challenge for researchers in this field will be to further develop adequate models.

Increased risk of Alzheimer's disease in Type II diabetes: insulin resistance of the brain or insulin-induced amyloid pathology?

Type II diabetes mellitus (DM2) is associated with an increased risk of cognitive dysfunction and dementia. The increased risk of dementia concerns both Alzheimer's disease and vascular dementia. Although some uncertainty remains into the exact pathogenesis, several mechanisms through which DM2 may affect the brain have now been identified. First, factors related to the ‘metabolic syndrome’, a cluster of metabolic and vascular risk factors (e.g. dyslipidaemia and hypertension) that is closely linked to DM2, may be involved. A number of these risk factors are predictors of cerebrovascular disease, accelerated cognitive decline and dementia. Secondly, hyperglycaemia may be involved, through adverse effects of potentially ‘toxic’ glucose metabolites on the brain and its vasculature. Thirdly, insulin itself may be involved. Insulin can directly modulate synaptic plasticity and learning and memory, and disturbances in insulin signalling pathways in the periphery and in the brain have recently been implicated in Alzheimer's disease and brain aging. Insulin also regulates the metabolism of β-amyloid and tau, the building blocks of amyloid plaques and neurofibrillary tangles, the neuropathological hallmarks of Alzheimer's disease. In this paper, the evidence for the association between DM2 and dementia and for each of these underlying mechanisms will be reviewed, with emphasis on the role of insulin itself.

Ageing and metabolism: drug discovery opportunities

There has recently been significant progress in our understanding of the mechanisms that regulate ageing, and it has been shown that changes in single genes can dramatically extend lifespan and increase resistance to many diseases. Furthermore, many of these genes belong to evolutionarily conserved pathways that also control energy metabolism. In this review, we describe the shared molecular machinery that regulates ageing and energy metabolism. Although drugs to slow ageing face severe regulatory hurdles, it is likely that an understanding of ageing pathways will help to identify novel drug targets to treat metabolic disorders and other age-related diseases.

Effects of exercise and diet on chronic disease

Currently, modern chronic diseases, including cardiovascular diseases, Type 2 diabetes, metabolic syndrome, and cancer, are the leading killers in Westernized society and are increasing rampantly in developing nations. In fact, obesity, diabetes, and hypertension are now even commonplace in children. Clearly, however, there is a solution to this epidemic of metabolic disease that is inundating today's societies worldwide: exercise and diet. Overwhelming evidence from a variety of sources, including epidemiological, prospective cohort, and intervention studies, links most chronic diseases seen in the world today to physical inactivity and inappropriate diet consumption. The purpose of this review is to 1) discuss the effects of exercise and diet in the prevention of chronic disease, 2) highlight the effects of lifestyle modification for both mitigating disease progression and reversing existing disease, and 3) suggest potential mechanisms for beneficial effects.

The epidemiologic study of dementia: a life-long quest?

Based on many experimental and observational studies we now understand that neurodegenerative brain changes begin by middle age. Characteristics of the risk factors for these brain changes may also change with age. A review is conducted of studies that report on the association of mid-life risk factors to late cognitive impairment and dementia. Issues related to the interpretation of the data are discussed. The studies suggest that mid-life cardiovascular risk factors, and in particular elevated levels of blood pressure, increase the risk for late-life cognitive impairment and dementia. Our understanding the contribution of cardiovascular risk factors to late age brain disease has been helped tremendously by prospective studies with long follow-up. To better understand which risk factors lead to disease initiation, progression and prognosis, a life course approach to the epidemiologic study of dementia is needed.