Midlife vascular risk factors and Alzheimer's disease in later life: longitudinal, population based study

Hypertension and cognition

Hypertension is a risk factor for stroke, ischemic white-matter lesions, cardiovascular disorders, and vascular dementia. This risk increases with increasing blood pressure. Several studies report that high blood pressure precedes Alzheimer's disease (AD) by decades, but blood pressure decreases the years before dementia onset and is lower in individuals with AD than in controls. High blood pressure has also been related to the neuropathological manifestations of AD. The exact mechanism behind these associations is not clear. Hypertension may cause cerebrovascular disease that may increase the likelihood that individuals with AD encephalopathy will express a dementia syndrome, this may accelerate the AD process, 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. Even if hypertension results only in a moderately increased risk of AD, or overall dementia, better treatment of hypertension may have an immense effect on the total number of individuals with dementia.

Vascular burden and BPSD: a reconceptualization

With increasing understanding of BPSD, the question of whether there are differences between BPSD of AD and VaD may be raised. The available evidence from the Cache County Study, the role of vascular risk factors in late-life depression, and vascular pathology in AD and VaD all converge to explore the impact of vascular burden on cerebral function and BPSD. This article argues that there may be domain differences in BPSD between AD and VaD and suggests that BPSVaD may be a concept to be pursued with possible useful clinical implications.

Reduction of serum LDL-C levels: a relationship to clinical benefits

The association between elevated serum cholesterol levels and cardiovascular risk was established several decades ago by studies such as the Framingham study and the Multiple Risk Factor Intervention Trial (MRFIT). Both primary and secondary prevention trials of cholesterol lowering, using HMG-CoA reductase inhibitors, have demonstrated clear benefits for lipid lowering in preventing both cardiovascular morbidity and mortality over a wide spectrum of coronary heart disease (CHD) risk. Even so, risk of events has been reduced by about 30% in these trials, leaving 70% of events occurring even in the presence of substantial cholesterol lowering. It is unknown whether further reduction of serum cholesterol levels will lower risk factors. The relationship between cholesterol lowering and cardiovascular risk, moreover, is not completely defined; it is unclear, at lower cholesterol levels, whether that relationship follows a threshold, a linear, or a curvilinear model. Early studies of low-density lipoprotein-cholesterol (LDL-C) lowering with HMG-CoA reductase inhibitors suggested that non-cardiovascular mortality might be increased at low serum LDL-C levels, however, these concerns have not been supported by subsequent clinical trials. Recent studies have shed further light on the potential benefits of lowering serum cholesterol levels beyond current guideline targets with HMG-CoA reductase inhibitors. More potent agents in development are likely to make such levels more readily achievable, as well as making guideline targets attainable for many of the large number of patients who currently fail to reach them.

Mild cognitive impairment: prevalence, prognosis, aetiology, and treatment

Mild cognitive impairment (MCI) is a recently described syndrome that is currently thought of as a transition phase between healthy cognitive ageing and dementia. Although this notion seems to be reasonable, the general nature of the term MCI--including its many definitions--makes accurate accounting of the prevalence, prognosis, and potential benefit from treatment somewhat difficult. The differences in cognitive profile and clinical progression among individuals with MCI are generally recognised. However, recent evidence also suggests that the aetiological heterogeneity among individuals with MCI could be greater than previously reported. For example, cerebrovascular disease seems to be underestimated as a potential cause of MCI. In this review, I attempt to recognise workable definitions of MCI to discuss the prevalence, pathophysiology, prognosis, and possibilities for treatment of this disorder.

Mild cognitive impairment in older people

CONTEXT

As public awareness of Alzheimer's disease increases, more people are asking for help and advice about memory problems. Memory complaints may be secondary to psychiatric, psychological, and physical conditions and is an almost universal early symptom of dementia. The concept of amnestic mild cognitive impairment attempts to describe those people in whom memory loss is not of such severity to merit a diagnosis of dementia. The importance of this group of people is not just the need to develop interventions which ameliorate individual suffering but that they represent a population at high risk of developing dementia, especially Alzheimer's disease, and are an appropriate target for dementia prevention strategies.

STARTING POINT

K Kantarci and colleagues (Dement Geriatr Cogn Disord 2002; 14: 198-207) looked at the diagnostic accuracy of magnetic-resonance hippocampal volumetry and spectroscopy in patients with mild cognitive impairment, in normal older people, and in patients with Alzheimer's disease. Hippocampal volumes and N-acetyl aspartate/creatine spectroscopy were the most sensitive assessments discriminating people with mild cognitive impairment from Alzheimer's disease. Combination assessments were better at discriminating these two groups from normal controls. The histological underpinning of cognitive symptoms in older people has been demonstrated by the Cognitive Function and Ageing study (Lancet 2001; 357: 169-75), which showed that a third of people with no clinical evidence of dementia had histopathological hallmarks of Alzheimer's disease. WHERE NEXT? 25 million people across the world have dementia. Mild cognitive impairment, if a validated concept, represents an opportunity for preventing dementia. As more information becomes available about the cause of Alzheimer's disease and prospects emerge for prevention, identification of predementia states offers considerable scope to reduce the individual and societal cost of the illness. Continued validation of the criteria for mild cognitive impairment and studies of intervention should be a priority. As more evidence becomes available highlighting the relatively arbitrary nature of dementia diagnosis (based largely on interference with activities) and interventions become available for the prevention of dementia, mild cognitive impairment and related conditions will become more important.

Induction of the cholesterol transporter ABCA1 in central nervous system cells by liver X receptor agonists increases secreted Abeta levels

The expression, function, and regulation of the cholesterol efflux molecule, ABCA1, has been extensively examined in peripheral tissues but only poorly studied in the brain. Brain cholesterol metabolism is of interest because several lines of evidence suggest that elevated cholesterol increases the risk of Alzheimer's disease. We found a largely neuronal expression of ABCA1 in normal rat brain by in situ hybridization. ABCA1 message was dramatically up-regulated in neurons and glia in areas of damage by hippocampal AMPA lesion after 3-7 days. Immunoblot analysis demonstrated ABCA1 protein in cultured neuronal and glial cells, and expression was induced by ligands of the nuclear hormone receptors of the retinoid X receptor and liver X receptor family. ABCA1 was induced by treatment with retinoic acid and several oxysterols, including 22(R)-hydroxycholesterol and 24-hydroxycholesterol. Expression of an ABCA1-green fluorescent protein construct in neuroblastoma cells demonstrated fluorescence in perinuclear compartments and on the plasma membrane. Because the Abeta peptide is important in Alzheimer's disease pathogenesis, we examined whether ABCA1 induction altered Abeta levels. Treatment of neuroblastoma cells with retinoic acid and 22(R)-hydroxycholesterol caused significant increases in secreted Abeta40 (29%) and Abeta42 (65%). Treatment with a nonsteroidal liver X receptor ligand, TO-901317, similarly increased levels of secreted Abeta40 (25%) and Abeta42 (126%). The increase in secreted Abeta levels was reduced by RNAi blocking of ABCA1 expression. These data suggest that the cholesterol efflux molecule ABCA1 may also be involved in the secretion of the membrane-associated molecule, Abeta.

Are antihypertensive agents protective against dementia? A review of clinical and preclinical data

In the United States, the size of the population of persons aged 65 years or older is expected to double within the next 30 years, resulting in a marked increase in the prevalence of dementia. Hypertension is a risk factor for cognitive impairment and dementia in addition to cerebrovascular morbidity and mortality. The evidence for a connection between high blood pressure in midlife and dementia in late life comes from numerous longitudinal studies. A placebo-controlled, double-blind, randomized trial involving 2,418 patients aged 60 years or older with isolated systolic hypertension demonstrated that active treatment based on the dihydropyridine calcium antagonist nitrendipine with the addition of enalapril, hydrochlorothiazide, or both if needed to control systolic blood pressure to <150 mmHg, significantly reduced not only stroke and cardiovascular complications but also the incidence of vascular dementia and Alzheimer's disease. Several trials of antihypertensive treatment are ongoing to confirm this important finding. The newer dihydropyridine calcium antagonists lacidipine and lercanidipine are effective and well tolerated in the treatment of hypertension. In animal models, these newer agents also have been shown to prevent the progression of hypertensive microvascular damage. Their neuroprotective effects offer possible unique advantages in the management of hypertension.

Hypertension and related factors in the etiology of Alzheimer's disease

The prevalence of hypertension is estimated to approach 50% in individuals above age 70. The consequences of hypertension include cerebrovascular disease, coronary heart disease, and general atherosclerosis. Several recent studies suggest that there may be an association also between hypertension and Alzheimer's disease (AD). This review will examine the evidence for this association and possible pathways between hypertension, Alzheimer encephalopathy, and clinical dementia.

Similarities and differences between Alzheimer's disease and vascular dementia from the viewpoint of nutrition

Dietary habits were compared in patients with Alzheimer's disease (AD) and those with vascular dementia (VaD). Twenty-seven patients with AD, 15 patients with VaD, and 49 age-matched controls were enrolled. Nutritional status was assessed using a semiquantified food-frequency questionnaire. Dietary habits were very similar in male patients with AD and VaD. Both groups had significantly higher energy intake than their energy demands: +25% for AD and +35% for VaD, respectively. However, major sources of energy were different: grains and animal fats for AD versus only grains for VaD. Calculation of nutrients revealed excess intake of n-6 polyunsaturated fatty acids (PUFA) and relative deficiencies of multiple vitamins including antioxidants, vitamin C and carotene, and the vitamin B group. In contrast, dietary habits in female patients with AD differed significantly from those of male patients. Female patients consumed significantly lower amounts of fish and green vegetables. Calculation of nutrients showed absolute deficiencies of n-3 PUFA, multiple vitamins, and minerals. Our results show that AD and VaD are similar from the viewpoint of nutrition, except for the higher consumption of animal fats for AD patients, probably reflecting Westernization of dietary habits in recent years. Nutrition may be relevant to the pathogenesis of dementia through many processes. Higher intake of energy and lower intake of antioxidants may exaggerate the process of dementia through oxidative stress. Excessive amounts of n-6 PUFA or deficiency of n-3 PUFA may cause chronic inflammation, platelet aggregation, or endothelial dysfunction of microvasculature. Nutrition may be useful for preventing dementia, although gender-specific differences must be taken into account.

Hemodynamic aspects of Alzheimer's disease

Neuroradiological functional imaging techniques demonstrate the patterns of hypoperfusion and hypometabolism that are thought to be useful in the differential diagnosis of Alzheimer's disease (AD) from other dementing disorders. Besides the distribution patterns of perfusion or energy metabolism, vascular transit time (VTT), vascular reactivity (VR), and oxygen extraction fraction (OEF), which can be measured with positron emission tomography (PET), provide hemodynamic aspects of brain pathophysiology. In order to evaluate the hemodynamic features of AD, PET studies were carried out in 20 patients with probable AD and 20 patients with vascular dementia (VaD). The PET findings were not included in their diagnostic process of AD. Using oxygen-15-labeled compounds, cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO(2)), OEF, cerebral blood volume, and VTT were measured quantitatively during resting state. To evaluate VR, CBF was also measured during CO(2) inhalation. There was a significant increase in OEF in and around the parietotemporal cortices, but both VTT and VR were well preserved in patients with AD. By contrast, VR was markedly depressed and VTT was mildly prolonged in patients with VaD. Thus, from the hemodynamic point of view, the preservation of vascular reserve may be a distinct difference between AD and VaD. Furthermore, this indicates a hemodynamic integrity of the vasculature in the level of arterioles in AD.

Therapeutic strategies for Alzheimer's disease

Alzheimer's disease is a progressive and ultimately fatal neurological disorder for which there is no effective treatment at present. The disease is characterized pathologically by cerebral plaques that contain the amyloid-beta peptide and thread-like neuronal structures composed of the microtubule-associated protein TAU. Both amyloid-beta and TAU are thought to be crucial to pathogenesis, but compelling evidence supports amyloid-beta as the 'prime mover'. The main efforts for developing therapeutics are therefore focused on preventing amyloid-beta production, aggregation or downstream neurotoxic events. The progress of these and other approaches raises the hope that effective agents for the prevention and treatment of Alzheimer's disease will be available in the near future.

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.

Longitudinal analysis of abnormal domains comprising mild cognitive impairment (MCI) during aging

Research directed towards early diagnosis and therapy of dementia demands rapid identification of prodromal mild cognitive impairment (MCI). A longitudinal study was designed to clarify whether different domains of cognitive impairment, tested by Mini-Mental State Examination (MMSE), help predict dementia. After 3.74+/-2.94 years of follow-up among 291 cognitively normative volunteers, 73 developed MCI. During the next 3.88+/-3.01 years of MCI follow-up, 47.9% of MCI developed dementia of Alzheimer's type (DAT), 20.5% of MCI developed vascular dementia (VaD) and 31.5% maintained persistent MCI at the time of data analysis. Total MMSE and subtest scores analyzed at MCI onset showed significant differences for serial seven subtest scores between DAT and persistent MCI (P<0.05). Rates of change in subtests of orientation and memory and total MMSE scores predicted DAT (P<0.01). Decreasing orientation and total MMSE scores predicted VaD conversion rates of MCI to DAT at 2 years were 20.06% among single-domain MCI versus 41.7% for multi-domain MCI (P<0.05). Subjects with MCI often have impaired cognitive domains other than memory and show rapid deterioration, which predicts DAT. VaD sometimes mimics DAT with subtle cognitive impairment appearing before onset of dementia.

Hypertension and hypercholesterolaemia as risk factors for Alzheimer's disease: potential for pharmacological intervention

This paper focuses on hypertension and hypercholesterolaemia as risk factors for Alzheimer's disease and, as such, subjects for prevention. The long-term, prospective, population-based studies regarding the relationship between hypertension or hypercholesterolaemia and Alzheimer's disease, and the clinical studies regarding the association between antihypertensive or lipid-lowering medications and the risk of Alzheimer's disease, are reviewed. These studies provide evidence to suggest that elevated blood pressure and cholesterol levels earlier in life may have an important role in the development and expression of late-life Alzheimer's disease. Based on these data, we propose that proper, early interventions aimed at reducing these cardiovascular risk factors may have an impact on the future incidence and prevalence of Alzheimer's disease.

Structural imaging in cognitive impairment and the dementias: an update

PURPOSE OF REVIEW

The purpose of this review is to explore and summarize recent advances in the structural imaging of cognitive impairment and the dementias. The focus is practical, covering issues that bear relevance to clinical practice or diagnosis. Findings in mild cognitive impairment, a state preceding but not necessarily leading to dementia, are discussed. Data from dementias other than Alzheimer's disease are reviewed at some length before outlining some novel issues in Alzheimer's disease imaging.

RECENT FINDINGS

A number of studies have proposed some medial temporal atrophy in mild cognitive impairment, and this may have some clinical value in predicting conversion to dementia. Data on other regions have also been proposed to predict conversion, but a number of studies on these regions have yielded entirely conflicting results. Data are also accumulating on the medial temporal lobe and other regions in non-Alzheimer's dementias.

SUMMARY

The medial temporal lobe is still the region of interest when studying mild cognitive impairment and Alzheimer's disease. Medial temporal atrophy, or lack thereof, may be of some diagnostic value even in non-Alzheimer's dementias. Medial temporal atrophy, however, is not an Alzheimer's disease-specific feature. One potential approach to improve the radiological diagnosis of dementia is mapping a number of regions in order to define patterns of atrophy. At present, however, the scarcity of existing data prevents unambiguous conclusions on this issue.

MRC/BHF Heart Protection Study of cholesterol lowering with simvastatin in 20,536 high-risk individuals: a randomised placebo-controlled trial

BACKGROUND

Throughout the usual LDL cholesterol range in Western populations, lower blood concentrations are associated with lower cardiovascular disease risk. In such populations, therefore, reducing LDL cholesterol may reduce the development of vascular disease, largely irrespective of initial cholesterol concentrations.

METHODS

20,536 UK adults (aged 40-80 years) with coronary disease, other occlusive arterial disease, or diabetes were randomly allocated to receive 40 mg simvastatin daily (average compliance: 85%) or matching placebo (average non-study statin use: 17%). Analyses are of the first occurrence of particular events, and compare all simvastatin-allocated versus all placebo-allocated participants. These "intention-to-treat" comparisons assess the effects of about two-thirds (85% minus 17%) taking a statin during the scheduled 5-year treatment period, which yielded an average difference in LDL cholesterol of 1.0 mmol/L (about two-thirds of the effect of actual use of 40 mg simvastatin daily). Primary outcomes were mortality (for overall analyses) and fatal or non-fatal vascular events (for subcategory analyses), with subsidiary assessments of cancer and of other major morbidity.

FINDINGS

All-cause mortality was significantly reduced (1328 [12.9%] deaths among 10,269 allocated simvastatin versus 1507 [14.7%] among 10,267 allocated placebo; p=0.0003), due to a highly significant 18% (SE 5) proportional reduction in the coronary death rate (587 [5.7%] vs 707 [6.9%]; p=0.0005), a marginally significant reduction in other vascular deaths (194 [1.9%] vs 230 [2.2%]; p=0.07), and a non-significant reduction in non-vascular deaths (547 [5.3%] vs 570 [5.6%]; p=0.4). There were highly significant reductions of about one-quarter in the first event rate for non-fatal myocardial infarction or coronary death (898 [8.7%] vs 1212 [11.8%]; p<0.0001), for non-fatal or fatal stroke (444 [4.3%] vs 585 [5.7%]; p<0.0001), and for coronary or non-coronary revascularisation (939 [9.1%] vs 1205 [11.7%]; p<0.0001). For the first occurrence of any of these major vascular events, there was a definite 24% (SE 3; 95% CI 19-28) reduction in the event rate (2033 [19.8%] vs 2585 [25.2%] affected individuals; p<0.0001). During the first year the reduction in major vascular events was not significant, but subsequently it was highly significant during each separate year. The proportional reduction in the event rate was similar (and significant) in each subcategory of participant studied, including: those without diagnosed coronary disease who had cerebrovascular disease, or had peripheral artery disease, or had diabetes; men and, separately, women; those aged either under or over 70 years at entry; and--most notably--even those who presented with LDL cholesterol below 3.0 mmol/L (116 mg/dL), or total cholesterol below 5.0 mmol/L (193 mg/dL). The benefits of simvastatin were additional to those of other cardioprotective treatments. The annual excess risk of myopathy with this regimen was about 0.01%. There were no significant adverse effects on cancer incidence or on hospitalisation for any other non-vascular cause.

INTERPRETATION

Adding simvastatin to existing treatments safely produces substantial additional benefits for a wide range of high-risk patients, irrespective of their initial cholesterol concentrations. Allocation to 40 mg simvastatin daily reduced the rates of myocardial infarction, of stroke, and of revascularisation by about one-quarter. After making allowance for non-compliance, actual use of this regimen would probably reduce these rates by about one-third. Hence, among the many types of high-risk individual studied, 5 years of simvastatin would prevent about 70-100 people per 1000 from suffering at least one of these major vascular events (and longer treatment should produce further benefit). The size of the 5-year benefit depends chiefly on such individuals' overall risk of major vascular events, rather than on their blood lipid concentrations alone.

Statins in the prevention and treatment of Alzheimer disease

Vascular risk factors such as hypertension and hypercholesterolemia during midlife increase the risk for Alzheimer's disease (AD). Treatment of hypercholesterolemia and other vascular risk factors may have great implications in the prevention of AD. Recent findings illustrate that the sterol metabolism in the brain is an active process, well controlled and regulated by 24-hydroxylase, an enzyme that is uniquely expressed in the brain. The use of statins in ischemic heart disease (IHD) has proven to be a phenomenal advance in pharmacological disease prevention and treatment. A growing body of evidence, suggest that statins exhibit additional benefits that are independent of their cholesterol-lowering actions. Statin treatment has also considerable effect in prevention of ischemic stroke. In animal models of ischemic stroke, statins have proven to reduce infarct size through up-regulation of endothelial nitric oxide synthases. Data from recent observational studies have revealed a potential role for statins in prevention of AD. The following review comments the processes leading to dementia including the involvement of cholesterol regulation, cerebral circulation and inflammation in development of dementia. The mechanisms by which statins may be beneficial in controlling these processes is discussed.

Association between high-density lipoprotein and cognitive impairment in the oldest old

Low high-density lipoprotein cholesterol is associated with an increased risk for cardiovascular disease and stroke. At the same time, cardiovascular disease and stroke are important risk factors for dementia. We assessed the association between total and fractionated cholesterol and cognitive impairment and explored whether observed associations were dependent on or independent of atherosclerotic disease. In a population-based study, total cholesterol, triglycerides, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol were measured in 561 subjects 85 years old and grouped in three equal strata representing decreasing serum concentrations. History of cardiovascular disease and stroke was determined. All subjects completed the Mini-Mental State Examination (MMSE), and the presence of dementia was determined. Median MMSE scores were significantly lower in subjects with low high-density lipoprotein cholesterol (25 points vs 27 points, p < 0.001). No differences in MMSE scores were found for other lipids and lipoproteins. MMSE scores in subjects with and without cardiovascular disease were 26 and 27 points (p = 0.007), respectively, and in subjects with and without stroke were 21 and 26 points (p < 0.001), respectively. The associations between low MMSE scores and low high-density lipoprotein cholesterol remained significant after subjects with cardiovascular disease or stroke were excluded. In a comparison of subjects with low high-density lipoprotein cholesterol with subjects with high high-density lipoprotein cholesterol, the odds ratio for dementia was 2.3 (95% confidence interval, 1.2-4.3), and in subjects without cardiovascular disease or stroke, it was 3.7 (95% confidence interval, 1.3-10.1). All odds ratios were unaffected by education, low-density lipoprotein cholesterol, triglycerides, and survival. Low high-density lipoprotein cholesterol is associated with cognitive impairment and dementia. At least part of the association between high-density lipoprotein cholesterol and cognitive function is independent of atherosclerotic disease.

Cerebrospinal fluid 24S-hydroxycholesterol is increased in patients with Alzheimer's disease compared to healthy controls

Experiments in cell cultures indicate that accumulation of cholesterol in hippocampal neurons results in an accelerated cleavage of amyloid precursor protein into amyloidogenic components. To be eliminated from the brain, cholesterol is converted to 24S-hydroxycholesterol which may reflect cerebral cholesterol turnover. We investigated cerebrospinal fluid (CSF) concentrations of 24S-hydroxycholesterol in a group of 14 Alzheimer's disease (AD) patients and ten healthy controls without any cognitive deficits or psychiatric or neurological disorders. To exclude potential effects of circulating plasma cholesterol on CSF 24S-hydroxycholesterol levels, only patients and controls with cholesterol levels in the normal range of 150-230 mg/dl were included. We found significantly elevated 24S-hydroxycholesterol CSF but not plasma levels in AD patients compared with healthy controls. Our results demonstrate that CSF 24S-hydroxycholesterol is increased in AD. This effect does not seem to be triggered by plasma cholesterol levels since the latter did not significantly differ between groups.

The relationship of hypertension in the elderly to AD, vascular dementia, and cognitive function

BACKGROUND

Hypertension at the age of 45 to 50 years may predispose to AD later in life. It is not known whether hypertension after age 65 years also contributes to AD risk, and its effect on cognitive function is also not fully understood.

METHODS

Data were analyzed from 1,259 Medicare recipients free of dementia in a longitudinal study covering a 7-year period (1991 to 1998). The effect of hypertension was first examined in relationship to the risk for incident AD and then to incident vascular dementia (VaD) using Cox proportional hazards models. Changes in performance over time on tasks of memory, language, and visuospatial/cognitive function were compared in those with and without hypertension using generalized estimating equations.

RESULTS

Of the 1,259 subjects, 731 (58.1%) had a history of hypertension associated with diabetes, stroke, and heart disease. A history of hypertension was not associated with an increased risk for AD (rate ratio [RR] 0.9, 95% CI 0.7 to 1.3) but was associated with an increased risk for VaD (1.8 [1.0 to 3.2]). Hypertension was not associated with changes in memory, language, and general cognitive function in normal individuals over time. Compared with individuals with neither hypertension nor heart disease, those with hypertension or heart disease alone had no increase in risk for VaD. However, when both were present, there was a threefold increase in risk for VaD. A sixfold increase in risk was observed when both hypertension and diabetes were present.

CONCLUSIONS

Hypertension after age 65 years is not associated with AD and does not adversely affect memory, language, or general cognitive function. A history of hypertension may be an antecedent to VaD, particularly in the presence of heart disease or diabetes.

Alzheimer disease as a vascular disorder: nosological evidence

BACKGROUND

The main stumbling block in the clinical management and in the search for a cure of Alzheimer disease (AD) is that the cause of this disorder has remained uncertain until now.

SUMMARY OF REVIEW

Evidence that sporadic (nongenetic) AD is primarily a vascular rather than a neurodegenerative disorder is reviewed. This conclusion is based on the following evidence: (1) epidemiological studies showing that practically all risk factors for AD reported thus far have a vascular component that reduces cerebral perfusion; (2) risk factor association between AD and vascular dementia (VaD); (3) improvement of cerebral perfusion obtained from most pharmacotherapy used to reduce the symptoms or progression of AD; (4) detection of regional cerebral hypoperfusion with the use of neuroimaging techniques to preclinically identify AD candidates; (5) presence of regional brain microvascular abnormalities before cognitive and neurodegenerative changes; (6) common overlap of clinical AD and VaD cognitive symptoms; (7) similarity of cerebrovascular lesions present in most AD and VaD patients; (8) presence of cerebral hypoperfusion preceding hypometabolism, cognitive decline, and neurodegeneration in AD; and (9) confirmation of the heterogeneous and multifactorial nature of AD, likely resulting from the diverse presence of vascular risk factors or indicators of vascular disease.

CONCLUSIONS

Since the value of scientific evidence generally revolves around probability and chance, it is concluded that the data presented here pose a powerful argument in support of the proposal that AD should be classified as a vascular disorder. According to elementary statistics, the probability or chance that all these findings are due to an indirect pathological effect or to coincidental circumstances related to the disease process of AD seems highly unlikely. The collective data presented in this review strongly support the concept that sporadic AD is a vascular disorder. It is recommended that current clinical management of patients, treatment targets, research designs, and disease prevention efforts need to be critically reassessed and placed in perspective in light of these important findings.

Cholesterol, A beta and Alzheimer's disease

Statins have been used for many years for the treatment of hypercholesterolemia. They lower low-density lipoprotein (LDL) cholesterol, increase high-density lipoprotein (HDL) levels and are considered to be very safe. Recently, a set of potential new applications was identified for statins. In the future, these drugs could be used to treat Alzheimer's disease (AD). Past studies have suggested a link between AD and lipids and a series of reports has recently been published that significantly tightens this link and also provides some explanations at the cellular level. This review focuses on these recent developments and perspectives that appear to link cholesterol, beta-amyloid and AD.

Cholesterol modulation as an emerging strategy for the treatment of Alzheimer's disease

The basis for therapeutic strategies targeting the amyloid-beta protein (Abeta) has come from studies showing that accumulation and aggregation of the Abeta within the brain is likely to cause Alzheimer's disease (AD). Along with an ever-increasing understanding of Abeta metabolism, many potential therapeutic strategies aimed at altering Abeta metabolism have emerged. Among the more intriguing targets for therapy are enzymes involved in cholesterol homeostasis, because it has been found that altering cholesterol can influence Abeta metabolism in experimental model systems, and that cholesterol-lowering agents, specifically HMG-CoA reductase inhibitors, could reduce the incidence of AD. It is likely that cholesterol influences Abeta metabolism in several ways, including altering Abeta production and perhaps altering Abeta deposition and clearance. Thus, pharmacological modulation of cholesterol levels could provide a relatively safe means to reduce Abeta accumulation in the brain, and thereby prevent or slow the development of AD.

Current awareness in geriatric psychiatry. Bibliography

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley &amp: Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of geriatric psychiatry. Each bibliography is divided into 9 sections: 1 Books, Reviews &amp: Symposia; 2 General; 3 Assessment; 4 Epidemiology; 5 Therapy; 6 Care; 7 Dementia; 8 Depression; 9 Psychology. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted

Statins for the reduction of risk of Alzheimer's disease

BACKGROUND

: Two recent clinical reports describe an association between statin therapy and a reduction in the occurrence of Alzheimer's disease by as much as 70 %. One report is a cross-sectional analysis of discharges among three hospitals, and the other is a nested case control study drawn from ambulatory patients of general practitioners in the UK. Because neither study is a randomized trial, the association noted between statin therapy and a reduced incidence of Alzheimer's disease may have occurred because other factors, unaccounted for in the studies, may be present (so called bias) and be responsible for the observed association. However, there is an expanding body of biological and epidemiological data that makes it plausible that statin therapy may retard or prevent the pathogenesis and clinical expression of Alzheimer's disease. This review was initiated in order to find other clinical evidence that might support or refute the hypothesized benefit of statin therapy.

OBJECTIVES

: The purpose is to review the evidence that treatment with statins reduces the risk of Alzheimer's disease.

SEARCH STRATEGY

: The following data bases were searched: Specialised Register of the Cochrane Dementia and Cognitive Improvement Group, MEDLINE (1966-2000/12), EMBASE (1980-2000/12), and Psych Info (1987-2000/11). Search terms included statins,lovastatin, pravastatin, simvastatin, alzheimer*, dement*, cogn*.

SELECTION CRITERIA

: In order to be selected, trials needed to be randomized, doubled blinded, and of sufficient duration( probably years rather than weeks or months) to ascertain the preventive potential of statin therapy.

DATA COLLECTION AND ANALYSIS

: Data were to be extracted independently by two reviewers and pooled where appropriate and possible. The pooled odds ratios (95% CI) or the average differences were to be estimated.

MAIN RESULTS

: There were no randomized trials found in the search.

REVIEWER'S CONCLUSIONS

: There is no good evidence to recommend statins for reducing the risk of Alzheimer's disease. There is, however, a growing body of biological, epidemiological, and limited but non-randomized clinical evidence that lowering serum cholesterol may retard the pathogenesis of Alzheimer's disease. Mounting the clinical studies to determine the potential benefit of statin therapy should be a high priority for future research agendas.