Midlife blood pressure and neuritic plaques, neurofibrillary tangles, and brain weight at death: the HAAS. Honolulu-Asia aging Study

Small hippocampal size in cognitively normal subjects with coronary artery disease

OBJECTIVE

Hippocampal size reduction detected by three-dimensional structural magnetic resonance imaging (3D-MRI) represents an important hallmark of Alzheimer's disease (AD). Recently, epidemiological and neuropathological studies have associated coronary artery disease (CAD) and cardiovascular risk factors with AD. The present study aimed to assess whether small hippocampal size is also a feature of CAD.

METHODS

Hippocampal volumes were assessed in 20 men with CAD and 20 healthy matched control subjects by use of 3D-MRI. Subjects with a history of neurological or psychiatric disorder, or signs of cognitive impairment were rigorously excluded.

RESULTS

Compared with controls, subjects with CAD had significantly smaller (-14%) hippocampal volumes. Cardiovascular risk factors were not related to hippocampal volumes of CAD subjects.

CONCLUSIONS

Our results demonstrate small hippocampal size in CAD subjects without any cognitive impairment. Future studies should clarify whether the annual rate of hippocampal volume loss of persons with CAD is greater than that of healthy individuals and predicts later cognitive decline or dementia.

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.

Diabetes and brain aging: epidemiologic evidence

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

The nature and effects of cortical microvascular pathology in aging and Alzheimer's disease

Age-related and amyloid-induced pathology of the cerebral microvasculature have been implicated as potential contributing factors to the pathogenesis of Alzheimer's disease (AD). The microvasculature plays a crucial role in maintaining brain homeostasis and deterioration of its integrity may have deleterious effects on brain function in AD, possibly leading to neurofibrillary degeneration, plaque formation, and cell loss. Brain vessels possess peculiar anatomical and physiological properties owing to their role in the exchange processes of various substances between blood and brain, which are highly regulated for the maintenance of ionic homeostasis of the neuronal environment. Here we review neuropathological aspects of cortical microvessels in aging and AD in relationship to known cardiovascular risk factors and their possible impact on the cognitive decline seen in late-onset dementia.

Vascular factors in dementia: an overview

Alzheimer's disease and cerebrovascular disease are two illnesses common to the elderly. Conventional wisdom has sought to separately describe and treat these two diseases. Accumulating evidence, however, shows that cerebrovascular risk factors may cause asymptomatic brain injury, share genetic risk with Alzheimer's disease and possibly accelerate the Alzheimer's process. Such evidence suggests that these two diseases may act additively or synergistically to cause clinical dementia. This review focuses on evolving data that support this hypothesis.

Effect of vascular lesions on cognition in Alzheimer's disease: a community-based study

OBJECTIVES

To investigate whether clinical and neuropathological differences exist between Alzheimer's disease (AD) cases with and without vascular lesions neuropathologically diagnosed using Consortium to Establish a Registry for Alzheimer's Disease (CERAD) criteria.

DESIGN

Descriptive observational study.

SETTING

A community-based registry that identified incident dementia cases.

PARTICIPANTS

Of the 124 subjects with available clinical and neuropathological assessments, 30 had AD lesions alone, and 18 had AD with vascular lesions. Patients with other neuropathological findings were excluded.

MEASUREMENTS

Dependent measures included demographic, clinical, and neuropathological characteristics. Neuropathological diagnoses were made using the CERAD criteria and Braak and Braak staging.

RESULTS

Of the 124 autopsied cases, 85 cases were diagnosed with neuropathological AD. Of these, 30 had pathology consistent with "pure" AD, whereas 18 had AD pathology with significant vascular lesions (AD/V). There were no differences in age, sex, or education between groups. AD/V cases had higher baseline and final Mini-Mental State Examination (MMSE) scores than pure AD cases, but after adjusting for education, differences in MMSE scores were not statistically significant. The AD/V group had significantly lower Braak staging than the pure AD group, after adjusting for education and final MMSE scores.

CONCLUSION

In this comparison study of AD cases with and without vascular lesions, AD/V cases had less severe AD pathology than those with AD alone, indicating that cerebrovascular disease likely contributes to the severity of cognitive impairment in those with AD. Controlling for vascular risk factors in patients with AD may have a significant effect on severity of dementia.

Aging, sexual dimorphism, and hemispheric asymmetry of the cerebral cortex: replicability of regional differences in volume

We examined age-, sex-, and hemisphere-related differences in the cerebral cortex. Volumes of the cerebral hemispheres and 13 regions of interest (ROIs) were measured on magnetic resonance images of 200 healthy adults. The strength of association between age and volume differed across ROIs. The lateral prefrontal cortex exhibited the greatest age-related differences, whereas significantly weaker associations were observed in the prefrontal white matter, sensory-motor, and visual association regions. The hippocampal shrinkage was significant in people in their mid-fifties. The primary visual, anterior cingulate, the inferior parietal cortices, and the parietal white matter showed no age-related differences. The pattern of age-related regional differences replicated the findings previously obtained on an independent sample drawn from the same population. Men evidenced larger volumes in all ROIs except the inferior parietal lobule, even after sexual dimorphism in body size was statistically controlled. In some regions (hippocampus and fusiform gyrus) men exhibited steeper negative age-related trends than women. Although a typical pattern of global hemispheric asymmetry was observed, the direction and magnitude of regional volumetric asymmetry was as inconsistent as in the previous reports. Thus, a pattern of age-related shrinkage suggesting increased vulnerability of the lateral prefrontal cortex to aging appears stable and replicable, whereas little consistency exists in sex-related and hemispheric differences in regional cortical volumes.

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

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

An active and socially integrated lifestyle in late life might protect against dementia

The recent availability of longitudinal data on the possible association of different lifestyles with dementia and Alzheimer's disease (AD) allow some preliminary conclusions on this topic. This review systematically analyses the published longitudinal studies exploring the effect of social network, physical leisure, and non-physical activity on cognition and dementia and then summarises the current evidence taking into account the limitations of the studies and the biological plausibility. For all three lifestyle components (social, mental, and physical), a beneficial effect on cognition and a protective effect against dementia are suggested. The three components seem to have common pathways, rather than specific mechanisms, which might converge within three major aetiological hypotheses for dementia and AD: the cognitive reserve hypothesis, the vascular hypothesis, and the stress hypothesis. Taking into account the accumulated evidence and the biological plausibility of these hypotheses, we conclude that an active and socially integrated lifestyle in late life protects against dementia and AD. Further research is necessary to better define the mechanisms of these associations and better delineate preventive and therapeutic strategies.

Magnetic resonance imaging of the brain in diabetes: the Cardiovascular Determinants of Dementia (CASCADE) Study

Diabetic patients are at increased risk for stroke, but little is known about the presence of other brain lesions. We studied the association of magnetic resonance imaging-detected brain lesions to diabetes in 1,252 individuals aged 65-75 years who were randomly selected from eight European population registries or defined working populations. All scans were centrally read for brain abnormalities, including infarcts, white matter lesions, and atrophy. We used a three-point scale to rate periventricular white matter lesions, and the volume of subcortical lesions was calculated according to their number and size. Subjective grading of cortical atrophy by lobe and summation of the lobar grades resulted in a total cortical atrophy score. The mean of three linear measurements of the ventricular diameter relative to the intracranial cavity defined the severity of subcortical atrophy. After adjustment for possible confounders, diabetes was associated with cortical brain atrophy but not with any focal brain lesions or subcortical atrophy. There was a strong interaction of diabetes and hypertension, such that the association between diabetes and cortical atrophy existed only in hypertensive but not in normotensive participants. Cognitive and pathological data are needed to determine the clinical significance of these findings as well as to understand the mechanisms underlying these associations.

Alzheimer’s Disease and Vascular Dementia

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

Epidemiology of neurodegeneration

Alzheimer's disease, Parkinson's disease, and motor neuron disease share a propensity to occur with increasing age and as either a sporadic or a familial disorder. A number of behavioral and environmental risk factors have been proposed for each disorder, but most associations lack consistency and specificity. Over the last decade the remarkable frequency of these disorders has become apparent, and the identification of mutations in genes has provided the means to understand their pathogenesis. Better and more accurate means to characterize and diagnose these diseases has greatly facilitated analytic epidemiology. The analysis of behavioral and genetic factors that may lower disease risk has led to clinical trials that are either in progress or being planned with the aim of preventing these disorders.

Combined effects of APOE genotype, blood pressure, and antihypertensive drug use on incident AD

OBJECTIVE

To study the hypotheses that APOE-epsilon4 allele may interact with blood pressure to affect Alzheimer's disease (AD) occurrence and that antihypertensive therapy could modify such an effect.

METHODS

A dementia-free cohort of 966 community-dwelling persons aged 75 years and older in Stockholm, Sweden was followed to detect patients with AD using the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition (DSM-III-R) diagnostic criteria. Data were analyzed using Cox proportional hazards models with adjustment for several potential confounders.

RESULTS

During a 6-year follow-up period, AD was diagnosed in 204 persons. APOE-epsilon4 allele, high systolic pressure (> or = 140 mm Hg), and low diastolic pressure (<70 mm Hg) were associated with an increased risk of AD. APOE-epsilon4 allele combined with low diastolic pressure greatly increased the risk of AD independent of antihypertensive drug use. Antihypertensive therapy significantly reduced the risk of AD regardless of APOE-epsilon4 status and counteracted the combined risk effect of the epsilon4 allele with high systolic pressure on the disease.

CONCLUSIONS

Elderly people with genetic susceptibility for Alzheimer's disease may experience a further increased disease risk if they have either high systolic pressure or low diastolic pressure. Antihypertensive therapy decreases the risk of Alzheimer's disease exerted by the APOE-epsilon4 allele.

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

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

The pleiotropic effects of HMG-CoA reductase inhibitors: their role in osteoporosis and dementia

HMG-CoA reductase is the rate-limiting enzyme for cholesterol synthesis and its inhibition exerts profound effects on cellular metabolism. Inhibitors of this enzyme are used in clinical practice to lower plasma cholesterol levels and are commonly collectively referred to as 'statins'. A number of in vitro, in vivo animal, and clinical studies suggest that properties of statins other than cholesterol lowering may be of biological importance. These diverse properties are often referred to as 'pleiotropic' and suggest that statins may affect a number of diseases of ageing. In this article we review the biological plausibility and clinical evidence of a role for statins in modulating two diseases of ageing: osteoporosis and dementia (including Alzheimer's disease). In both diseases, there is a sound cellular and laboratory basis for a plausible therapeutic effect of statins. In the case of osteoporosis, there are conflicting data regarding clinical benefit, with both negative and positive results reported. In particular, secondary analyses of randomised, controlled studies have shown no reduction of fracture risk by statins. In the case of dementia there are fewer clinical studies but there is clear anticipated benefit in macrovascular dementias attributable to statin-mediated reduction of the risk of stroke. Overall, there are a lack of prospective, placebo-controlled, randomised data testing statins and modulation of the risk of osteoporosis-related fracture or of clinical dementia, where these are primary outcomes. Until such data are available, the use of statins appears promising but cannot be recommended as a primary therapeutic modality for either condition.

Association between blood pressure levels over time and brain atrophy in the elderly

The relation between blood pressure level and degree of global brain atrophy is equivocal. We evaluated past and present blood pressure levels and change in blood pressure over 20 years in relation to the degree of cortical atrophy on magnetic resonance imaging (MRI). In 1995-1996, we measured blood pressure and performed MRI in 1077 nondemented elderly (age 60-90 years). For 513 of these, we had information on a blood pressure level 20 years before. The degree of cortical atrophy was semi-quantitatively scored (range 0-15). In late life, a high (>/=90 mmHg) and low (<65 mmHg) diastolic blood pressure were associated with more cortical atrophy than a diastolic blood pressure level between 65-74 mmHg (adjusted difference 0.60 units (95% confidence interval (CI), 0.18-1.02) and 0.77 units (0.28-1.25), respectively). Persons whose diastolic blood pressure had declined more than 10 mmHg over 20 years had more cortical atrophy than those with stable blood pressure levels (adjusted difference 0.53 units, 0.05-1.02). Both high and declining diastolic blood pressure levels are associated with more global brain atrophy on MRI.

Transient ischaemic attacks are associated with increased rates of global cerebral atrophy

OBJECTIVES

To determine whether patients presenting with a first transient ischaemic attack (TIA) subsequently show increased rates of brain atrophy compared with age matched controls; and to assess potential risk factors for brain atrophy in this group.

METHODS

60 patients with a first, isolated TIA and 26 age and sex matched controls were recruited. None had evidence of cognitive impairment. Vascular risk factors were treated appropriately. All subjects had volumetric imaging at the start of the study and one year later, when they were clinically reassessed. TIA patients also had serial dual echo brain imaging. Rates of whole brain atrophy were calculated from the registered volumetric scans, as was the incidence of new ischaemic lesions. In the TIA group, the degree of white matter disease was assessed. Atrophy rates and blood pressure were compared between patients and controls.

RESULTS

22 patients (37%) developed new "clinically silent" infarcts during follow up. The mean (SD) annualised percentage atrophy rate in the TIA group was significantly higher than in the controls, at 0.82 (0.39)% v 0.33 (0.3)% (p < 0.0001). In the TIA group, diastolic blood pressure (p = 0.004) and white matter disease severity (p < 0.001) were correlated with cerebral atrophy rate. Increased white matter disease was found in patients in whom new ischaemic lesions developed (p < 0.001).

CONCLUSIONS

Patients presenting with a first TIA have excess global brain atrophy compared with age matched controls over the subsequent year. Increased atrophy rates following a TIA may be directly or indirectly related to increasing white matter disease and diastolic hypertension. Future studies should assess whether this atrophy inevitably leads to cognitive decline, and whether aggressive treatment of risk factors for cerebrovascular disease (particularly hypertension) after a TIA can influence outcome.

Relationship between blood pressure and Alzheimer's disease in Linxian County, China

To investigate the relationship between hypertension and Alzheimer's disease(AD) and the change of Alzheimer's patients' blood pressure(BP) before and after the onset of AD, we conducted this epidemiological study. Subjects for this study were individuals who participated in a large scale, randomized controlled trial of nutritional intervention from 1984 to 1991. Participants were initially screened for dementia using Chinese Mini-Mental State Examination (CMMS) and Activities of Daily Living (ADL). Positive subjects were subsequently administered a detailed neuropsychological and neurobehavioral examination. The diagnosis of AD was made by a consensus conference of psychiatrists using Diagnostic And Statistical Manual Of Mental Disorders-Fourth Edition(DSM-IV) criteria. 16488 subjects were examined and 301 were diagnosed as AD. We compared the prevalence of AD in different populations that were stratified with 1984's systolic or diastolic blood pressure(those four stratifications being high blood pressure, borderline blood pressure, normal, low blood pressure), and compared the change of blood pressure of 301 AD patients between 1984 and 1999-2000, which is before and after the onset of AD respectively. Multiple Logistic Regression (1:1 nested case-control study) was used to assess if hypertension is an independent risk factor for AD, and Trend test was used to assess the relationship between blood pressure and AD. Here we demonstrate that there was a significant difference in AD prevalence among different populations stratified by systolic or diastolic blood pressure (P < 0.01). The prevalence is highest in hypertension group, and lowest in hypotension group. Multiple Logistic Regression identified high blood pressure as a risk factor for AD (OR = 1.97, 95%CI:1.09-3.54, P = 0.02). Trend test showed that there is a significant dose-response relationship between blood pressure and AD (P < 0.0002). For hypertensive AD patients, there was no significant difference in systolic blood pressure(SBP) before and after the onset of AD, but diastolic blood pressure(DBP) decreased dramatically after the onset of AD (P < 0.01); however, the result also showed that DBP decrease occurred in the non-demented group. Based on this, we think the DBP decrease is not related to AD. We further investigated whether BP values differed crossed-sectionally between the AD-patients and non-demented individuals. We found that regardless of SBP or DBP, the BP values of the AD group were all significantly higher than that of non-demented. In summary, these data suggest there is a strong relationship between hypertension and AD; however, the mechanism remains to be studied.

Proton magnetic resonance spectroscopy reveals similar white matter biochemical changes in patients with chronic hypertension and early Alzheimer's disease

OBJECTIVES

Hypertension is a risk factor for dementia and is associated with some of the brain changes that are found in Alzheimer's disease and other neurodegenerative diseases, such as atrophy and neurofibrillary tangles. We evaluated the cerebral white matter biochemical pattern in healthy older subjects, older patients with chronic hypertension, and patients with Alzheimer's disease (AD) using proton magnetic resonance spectroscopy (1H-MRS).

DESIGN

Cross-sectional study.

SETTING

University-affiliated outpatient clinic.

PARTICIPANTS

Ten healthy older subjects, 10 cognitively intact older patients with chronic hypertension, and 10 older patients with early AD.

MEASUREMENTS

All subjects underwent clinical examination, neuropsychological assessment, and 1H-MRS to measure N-acetylaspartate (NAA), myoinositol, choline, and creatine resonance signals in an 8-cm3 voxel located in the paratrigonal white matter region bilaterally. NAA/creatine, myoinositol/creatine, and choline/creatine ratios were measured, and the mean values were compared using one-way analysis of variance with Tukey test for post hoc analysis.

RESULTS

A significantly higher mean myoinositol/creatine (ratio +/- standard deviation) was found in hypertensive patients (0.67 +/- 0.05) and in AD patients (0.68 +/- 0.08) than in controls (0.56 +/- 0.04) (P <.001). Conversely neither NAA/creatine ratio nor choline/creatine ratio differed among the three groups.

CONCLUSIONS

In this study, cognitively intact chronic hypertensive older patients had a higher white matter myoinositol/creatine ratio compared with healthy older subjects, suggesting that myoinositol may be a sensitive marker of the effects of chronic hypertension on the brain. Moreover, the similar increase of myoinositol/creatine ratio in patients with hypertension and in those with early AD provides further evidence of common brain changes with these conditions.

The relationship between temporal changes in blood pressure and changes in cognitive function: atherosclerosis risk in communities (ARIC) study

BACKGROUND

Although previous epidemiological studies have reported that hypertension is a major risk factor for decline in brain perfusion and atrophy, which are known to be related to cognitive decline, the impact of temporal changes in blood pressure on age-related cognitive declines has not been assessed.

METHODS

The present study evaluates changes in blood pressure and cognitive decline over a 6-year period in the Atherosclerosis Risk in Communities (ARIC) Study. This report is based on 8,058 men and women aged 48-67 years examined in the second (1990-92), and fourth (1996-98) ARIC cohort visits. Changes between these visits were measured in hypertension status and three cognitive function tests: Delayed Word Recall (DWR), the Digit Symbol Subtest of the Wechsler Adult Intelligence Scale-Revised (DSS/WAIS-R), and the Word Fluency (WF). Adjusted mean differences in cognitive function were compared among five categories of hypertension status by using linear regression modeling.

RESULTS

In the present study, older subjects with uncontrolled hypertension had a significantly larger mean DSS/WAIS-R score decline than normotensive subjects. Although other cognitive declines did not achieve statistical significance, both cross-sectional and change analysis suggested that partially controlled or uncontrolled hypertension is associated with a less favorable cognitive profile, particularly when considering results of the DSS and the WF tests.

CONCLUSIONS

The present study results provide some support to the hypothesis that hypertension status changes over 6 years in individuals initially aged 48-67 years are related to cognitive changes.

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.

Type 2 diabetes, APOE gene, and the risk for dementia and related pathologies: The Honolulu-Asia Aging Study

Type 2 diabetes may be a risk factor for dementia, but the associated pathological mechanisms remains unclear. We evaluated the association of diabetes alone or combined with the apolipoprotein E (APOE) gene with incident dementia and neuropathological outcomes in a population-based cohort of 2,574 Japanese-American men enrolled in the Honolulu-Asia Aging Study, including 216 subjects who underwent autopsy. Type 2 diabetes was ascertained by interview and direct glucose testing. Dementia was assessed in 1991 and 1994 by clinical examination and magnetic resonance imaging and was diagnosed according to international guidelines. Logistic regression was used to assess the RR of developing dementia, and log-linear regression was used to estimate the incident rate ratio (IRR) of neuropathological outcomes. Diabetes was associated with total dementia (RR 1.5 [95% CI 1.01-2.2]), Alzheimer's disease (AD; 1.8 [1.1-2.9]), and vascular dementia (VsD; 2.3 [1.1-5.0]). Individuals with both type 2 diabetes and the APOE epsilon4 allele had an RR of 5.5 (CI 2.2-13.7) for AD compared with those with neither risk factor. Participants with type 2 diabetes and the epsilon4 allele had a higher number of hippocampal neuritic plaques (IRR 3.0 [CI 1.2-7.3]) and neurofibrillary tangles in the cortex (IRR 3.5 [1.6-7.5]) and hippocampus (IRR 2.5 [1.5-3.7]), and they had a higher risk of cerebral amyloid angiopathy (RR 6.6, 1.5-29.6). Type 2 diabetes is a risk factor for AD and VsD. The association between diabetes and AD is particularly strong among carriers of the APOE epsilon4 allele. The neuropathological data are consistent with the clinical results.