Vascular dementia : incidence and risk factors in the Canadian study of health and aging

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.

Alcohol consumption and risk of dementia: the Rotterdam Study

BACKGROUND

Light-to-moderate alcohol consumption reduces the risk of coronary heart disease and stroke. Because vascular disease is associated with cognitive impairment and dementia, we hypothesised that alcohol consumption might also affect the risk of dementia.

METHODS

We examined the relation between alcohol consumption and risk of dementia in individuals taking part in the Rotterdam Study--a prospective population-based study of 7983 individuals aged 55 years and older. We studied all participants who did not have dementia at baseline (1990-93) and who had complete data on alcohol consumption (n=5395). Through follow-up examinations in 1993-94 and 1997-99 and an extensive monitoring system, we obtained nearly complete follow-up (99.7%) until the end of 1999. We used proportional hazards regression analysis, adjusted for age, sex, systolic blood pressure, education, smoking, and body-mass index, to compare the risk of developing dementia between individuals who regularly consumed alcohol and individuals who did not consume alcohol.

FINDINGS

The average follow-up was 6.0 years. During this period, 197 individuals developed dementia (146 Alzheimer's disease, 29 vascular dementia, 22 other dementia). The median alcohol consumption was 0.29 drinks per day. Light-to-moderate drinking (one to three drinks per day) was significantly associated with a lower risk of any dementia (hazard ratio 0.58 [95% CI 0.38-0.90]) and vascular dementia (hazard ratio 0.29 [0.09-0.93]). We found no evidence that the relation between alcohol and dementia varied by type of alcoholic beverage.

INTERPRETATION

These findings suggest that light-to-moderate alcohol consumption is associated with a reduced risk of dementia in individuals aged 55 years or older. The effect seems to be unchanged by the source of alcohol.

Incidence of dementia, Alzheimer's disease, and vascular dementia in Italy. The ILSA Study

OBJECTIVES

To estimate the incidence of dementia, Alzheimer's disease (AD), and vascular dementia (VaD) in older Italians and evaluate the relationship of age, gender, and education to developing dementia.

DESIGN

Cohort incidence study in the context of the Italian Longitudinal Study on Aging.

SETTING

Population sample from eight Italian municipalities.

PARTICIPANTS

A dementia-free cohort of 3,208 individuals (aged 65-84), individuated after a baseline evaluation performed in 1992 / 93, aimed at detecting prevalent cases.

MEASUREMENTS

The dementia-free cohort was reexamined in 1995 to identify incident cases. The Mini-Mental State Examination (cutoff 23 / 24) was employed to screen for dementia. Trained neurologists evaluated the individuals who screened positive. Final diagnoses had to meet Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised criteria for dementia, National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for AD, and International Classification of Diseases, Tenth Revision criteria for VaD.

RESULTS

Before the follow-up examination, 382 individuals had died (232 had reliable information). Of the 2,826 survivors, 2,266 completed the study. Overall, 127 new dementia cases were identified. Average incidence rates per 1,000 person-years were 12.47 (95% confidence interval (CI)=10.23-14.72) for dementia, 6.55 (95% CI=4.92-8.17) for AD, and 3.30 (95% CI=2.14-4.45) for VaD. Both AD and VaD showed age-dependent patterns. Education was protective against dementia and AD. Women carried a significantly higher risk of developing AD (hazard ratio=1.67, 95% CI=1.02-2.75), and men of developing VaD (hazard ratio=2.23, 95% CI=1.06-4.71).

CONCLUSIONS

Incidence of dementia in Italy paralleled that in most industrialized countries. About 150,000 new cases per year are expected. A significant gender effect was evidenced for major dementia subtypes. The burden of VaD, especially in men, offers opportunities for prevention.

History of depression as a risk factor for dementia: an updated review

OBJECTIVE

This review updates an earlier meta-analysis of the data on history of depression as a risk factor for dementia. It also considers the available evidence on the hypotheses proposed to explain the association between history of depression and dementia.

METHOD

A meta-analysis was carried out on results from seven case-control and six prospective studies. A qualitative review was carried out on the evidence related to the hypotheses to explain the association.

RESULTS

The meta-analysis found evidence to support an association from both case-control studies (estimated relative risk 2.01; 95% CI 1.16-3.50) and prospective studies (estimated relative risk 1.87; 95% CI 1.09-3.20). However, the evidence did not clearly support any one hypothesis explaining the association. The most likely contenders are: (i) depression can be an early prodrome of dementia, (ii) depression brings forward the clinical manifestation of dementing diseases, and (iii) depression leads to damage to the hippocampus through a glucocorticoid cascade.

CONCLUSIONS

The possibility that history of depression is a risk factor for dementia needs to be taken seriously and explanations of the association need to be further researched.

Incidence of dementia: does gender make a difference?

Several studies suggested that women are at higher risk of dementia than men. However, that was based on rather limited data. We investigated possible gender differences in the incidence of dementia, Alzheimer's disease and vascular dementia, in the Rotterdam Study, a large population based prospective cohort study in the Netherlands of 7,046 persons aged 55 years and older, free of dementia at baseline. In 40,441 person-years of follow-up (mean 5.7 years) we identified 395 new cases of dementia (overall incidence: 9.8 per 1,000 person-years). Alzheimer's disease was the most frequent subtype of dementia (293 cases; 7.2 per 1,000). Vascular dementia was diagnosed in 57 participants (1.5 per 1,000). Overall, dementia incidence was similar for men and women (rate ratio women versus men: 1.00, 95% CI: 0.80-1.24). However, after 90 years of age dementia incidence declined in men but not in women (rate ratio 2.61, 95% CI: 1.04-6.56), in particular for Alzheimer's disease (rate ratio 5.79, 95% CI: 1.40-23.90). The overall incidence of vascular dementia was lower in women than in men (rate ratio 0.57, 95% CI: 0.34-0.97). This large population-based study suggests no gender differences in the incidence of dementia up to high age. After 90 years of age the incidence of Alzheimer's disease is higher for women than for men. The incidence of vascular dementia is higher for men than for women in all age groups.

Heart disease and vascular risk factors in the cognitively impaired elderly: implications for Alzheimer's dementia

The term "cardiogenic dementia" was introduced a few decades ago to indicate an alteration of consciousness and cognition due to heart disease. Although this term is now disused, the relationship between cardiovascular disease and cognitive impairment is currently of great interest, not only for its potential therapeutic implications. but also for the recently recognized important role that vascular factors appear to play in Alzheimer's disease. The aims of this review are therefore 1) to show data supporting the role of cardiac disease--namely congestive heart failure, myocardial infarction and atrial fibrillation--and other vascular risk factors--i.e., hypertension and diabetes--in the development or worsening of cognitive impairment; 2) to highlight recent observations on the relationship between presence and severity of congestive heart failure/ myocardial infarction/atrial fibrillation and Alzheimer's disease: and 3) to uncover the type of studies needed in this field in order to facilitate a more precise algorithm of dementia prevention as well as intervention in demented patients with cardiovascular disease.

Clinical Research on Older Adults in Canada: Summary of Recent Progress

Geriatric Medicine is a young specialty in Canada, having been formally recognized in 1981. The early years of research chiefly involved designing and describing programs of care. As the specialty matured, so too did the nature of research into the clinical problems of older adults. This article discusses research published by Canadian geriatricians since 1998, the date of a previous review. Two prominent areas of research are frailty and dementia. Several groups have studied the natural history of frailty, and designed techniques to better measure outcomes. Interventional trials are also gaining prominence, with the Systeme de services intégrés pour personnes agees en perte d'automonie (SIPA) and Mobile Geriatric Assessment Team (MGAT) being good examples. The Canadian Study of Health and Aging (CSHA) is one of the largest studies of dementia epidemiology ever conducted, and the upcoming third wave will provide new data on the outcomes of cognitive impairment not meeting criteria for dementia. Other areas of interest include pharmacoepidemiology, difficult clinical problems, advanced directives and bioethics. Canadian research in geriatrics will continue to develop, with the establishment of the Canadian Institutes of Health Research providing exciting new opportunities.