Inter-rater reliability of the diagnosis of vascular cognitive impairment at a memory clinic

Consensus criteria for the diagnosis of vascular dementia (VaD) are gradually being replaced with data-based criteria. We report the inter-rater reliability of a new set of empirically-derived criteria for vascular cognitive impairment (VCI). Stratified sampling, with optimal allocation, was employed to randomly select 36 patients from the Queen Elizabeth II Health Science Centre's Memory Disability Clinic. Chart reviews were conducted independently by 4 physicians. Each physician classified the patients as having either: no cognitive impairment, VCI or Alzheimer's disease (AD). VCI was further classified both clinically (VCI without dementia, VaD or AD with a vascular component) and radiographically (infarcts, white matter changes, single strategic stroke). The intraclass correlation coefficient (ICC) for the diagnosis by physicians of VCI or otherwise was based on a repeated-measures analysis of variance with raters as the independent variable. A significant coefficient of reliability (average ICC = 0.88, 95% CI = 0.80-0.93) was obtained (H(o): rho </= 0.80, p = 0.03). Where differences in diagnosis occurred, the discrepancies most commonly resulted within the subtypes of VCI (9 cases) or between the diagnoses of AD and VCI (9 cases). Instances of diagnostic incongruity were typically due to the disagreement of a single rater (10 cases). This study demonstrates a high degree of reliability of criteria for VCI by physicians in a memory clinic, and can also be understood as an aspect of construct validation of those criteria. In the absence of a readily available biological marker for VCI, clinical criteria are necessary and can be reliably employed.

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

BACKGROUND AND PURPOSE

Very few population-based studies have systematically examined incident vascular dementia (VaD). From the Canadian Study of Health and Aging cohort, incidence rates of VaD were determined and risk factors analyzed.

METHODS

This was a cohort incidence study that followed 8623 subjects presumed to be free of dementia over a 5-year period. The risk factors were examined with a nested prospective case-control study. Exposure was determined by means of a risk factor questionnaire administered to the subject or a proxy at the beginning of the study.

RESULTS

On the basis of 38 476 person-years at risk, the annual incidence rate was estimated to be 2.52 per thousand undemented Canadians (95% CI 2. 02 to 3.02). Including an estimation of the probability of VaD among the decedents, this figure rose to 3.79. For the risk factors study, 105 incident cases of VaD according to the NINCDS-AIREN criteria were compared with 802 control subjects. Significant risk factors were: age (OR=1.05), residing in a rural area (2.03), living in an institution (2.33), diabetes (2.15), depression (2.41), apolipoprotein E epsilon4 (2.34), hypertension for women (2.05), heart problems for men (2.52), taking aspirin (2.33), and occupational exposure to pesticides or fertilizers (2.05). Protective factors were eating shellfish (0.46) and regular exercise for women (0.46). There was no relation with sex, education, or alcohol.

CONCLUSIONS

The study confirmed some previously reported risk factors but also suggested new ones. It raised concerns about the prescription of aspirin and perhaps other factors related to rural life.

Interrater reliability of the Clinical Dementia Rating in a multicenter trial

OBJECTIVE

To test the interrater reliability of the Clinical Dementia Rating (CDR) in a multicenter clinical trial.

DESIGN

Observational study.

SETTING

Training session for a multicenter trial of milameline, a direct muscarinic agonist, in the treatment of Alzheimer's disease.

PARTICIPANTS

Twenty-four raters (physicians and nurses) familiar with drug trials and expert in the care of patients with Alzheimer's disease.

METHODS

Independent scoring of the CDR using four videotaped CDR interviews.

OUTCOME MEASURE

Interrater reliability, as tested by the Kappa statistic

RESULTS

The overall interrater reliability was 0.62. Within the CDR domains, the global kappas ranged from 0.33 +/- 0.06 to 0.88 +/- 0.06.

CONCLUSIONS

The data support moderate to high overall interrater reliability but show important difficulties in the reliable assessment of early dementia.

Limitations of clinical criteria for the diagnosis of vascular dementia in clinical trials. Is a focus on subcortical vascular dementia a solution?

Vascular dementia (VaD) includes several different vascular mechanisms and changes in the brain, and has different causes and clinical manifestations. Critical to its conceptualization and diagnosis are definitions of the cognitive syndrome, vascular etiologies, and changes in the brain. Variation in these has resulted in different definitions of VaD, estimates of prevalence, and types and distribution of brain lesions. This definitional heterogeneity may have been a factor for negative results in prior clinical trials on VaD. We propose that the division of VaD into subtypes can identify a more homogeneous group of patients for drug trials. A so-called "subcortical" VaD could incorporate two old clinical entities "Binswanger's disease" and "the lacunar state." Small vessel disease is the primary vascular etiology, lacunar infarcts and ischemic white matter lesions are the primary type of brain lesions, the subcortical areas and frontal connections are the primary location of lesions, and a subcortical syndrome as the primary clinical manifestation. The clinical syndromes are likely more variable, and urgently need to be categorized. Selection of these patients for clinical trials could mainly be based on brain imaging features, where the essential changes and the main aspects of the lesions include extensive ischemic white matter lesions and lacunar infarcts in the deep gray and white matter structures. Subcortical VaD is expected to show a more predictable clinical picture, natural history, outcomes, and treatment responses.

The association between parkinsonism, Alzheimer's disease, and mortality: a comprehensive approach

BACKGROUND

The impact of parkinsonism on survival in older persons independent of dementia is not well understood.

METHODS

Participants in the clinical examination of the Canadian Study of Health and Aging who had parkinsonism and were older than age 65 were identified. The impact of parkinsonism on 5-year survival was determined for a combined cohort with and without dementia, and a stratified analysis was then conducted for the subgroups with Alzheimer's disease (AD) and those without dementia. Subjects with a previous diagnosis of Parkinson's disease and those prescribed drugs causing extrapyramidal side effects were excluded.

FINDINGS

A total of 721 subjects with AD and 1705 subjects without dementia were examined. After adjusting for age and residential status (community vs institution), parkinsonism was associated with poorer survival in the combined cohort (risk ratio 1.51; 95% CI, 1.22-1.85), in those with AD (risk ratio 1.34; 95% CI, 1.02-1.76), and those without dementia (risk ratio 1.54; 95% CI, 1.11-2.15). In the combined cohort, parkinsonism remained independently associated with higher mortality after adjusting for AD status (risk ratio 1.39; 95% CI, 1.13-1.72). In the subgroup with AD, parkinsonism remained associated with poorer survival after adjusting for severity of cognitive impairment (risk ratio 1.33; 95% CI. 1.04-1.74).

INTERPRETATION

Parkinsonism is significantly associated with poorer survival in older persons, regardless of whether they have dementia.

The diagnosis of "mixed" dementia in the Consortium for the Investigation of Vascular Impairment of Cognition (CIVIC)

If vascular risk factors are risk for Alzheimer's disease (AD), and if "pure" vascular dementia (VaD) is less common than has been thought, what do we make of the diagnosis of mixed dementia? We report characteristics of those with mixed dementia in a prospective, seven center, clinic-based Canadian study. Of 1,008 patients, 372 were diagnosed with AD, 149 with vascular cognitive impairment (VCI) including 76 with mixed AD/VaD, and 82 with other types of dementia. The mean age of patients with mixed AD/VaD was 78.0 +/- 7.6 years; 49% were female. These proportions differed significantly between dementia diagnosis subgroup (p < 0.001) showing a trend which is evident in all comparisons--AD/VaD patients fall in between AD and VaD. Vascular risk factors were present significantly more often in mixed AD/VaD than in AD (p < 0.001). More mixed AD/VaD (20%) than AD patients (4%) had focal signs, compared with 38% of those with vascular dementia and 12% with other types of dementia. Between the initial clinical diagnosis and the final diagnosis (which utilized neuroimaging and neuropsychological data) AD/VaD was the least stable diagnosis. Neuroimaging of ischemic lesions was the most common reason for reassignment from AD to the mixed AD/VaD diagnosis (17 cases). These data suggest that an operational definition of mixed AD/VaD can be proposed on presentation and clinical/radiographic findings, but indifferent to vascular risk factors. The concept of mixed dementia should be extended to include vascular dementia in combination with dementias, other than Alzheimer's disease.

Incidence and outcomes of diabetes mellitus in elderly people: report from the Canadian Study of Health and Aging

BACKGROUND

The epidemiology of diabetes in elderly people is not well understood. The purpose of this study was to estimate the incidence of diabetes mellitus among elderly people in Canada and the relative risks of death and admission to an institution among elderly diabetic patients.

METHODS

The study was a secondary analysis of data for a community-dwelling sample from the Canadian Study of Health and Aging, a nationwide representative cohort study of 9008 elderly people (65 years of age or older at baseline) in Canada. Diabetes was identified primarily by self-reporting, and a clinician's diagnosis and the presence of treatments for diabetes were used to identify diabetic patients who did not report that they had the condition.

RESULTS

The reliability of self-reported diabetes (the kappa statistic) was 0.85. The estimated annual incidence of diabetes was 8.6 cases per thousand for elderly Canadians. Incidence decreased with age, from 9.5 for subjects 65-74 years of age, to 7.9 for those 75-84 years of age and then to 3.1 for those 85 years of age and older. Diabetes was associated with death (relative risk 1.87, 95% confidence interval 1.59-2.19) and admission to an institution (relative risk 1.58, 95% confidence interval 1.28-1.94).

INTERPRETATION

Diabetes mellitus is common among elderly people, but the incidence declines among the very old.

Feasibility and measurement properties of the functional reach and the timed up and go tests in the Canadian study of health and aging

BACKGROUND

Physical performance measures may offer advantages over self-report in the functional assessment of older people. Estimates of the feasibility, reliability, and construct validity of these measures in large, heterogeneous samples are necessary to establish their importance relative to traditional measures of function.

METHODS

Analysis of clinical data from Phase 2 of the Canadian Study of Health and Aging, a nation-wide representative survey of elderly people in Canada (N = 2,305).

RESULTS

Both physical performance measures proved infeasible in many subjects (29.3% for the Timed Up and Go [TUG], 35.9% for the Functional Reach [FR]). Cognitive impairment was the most important determinant of inability to complete the tests. For those able to complete the tests, cognitively unimpaired subjects could reach farther (median 29 cm) and complete the TUG in less time (median 12 seconds) than those cognitively impaired (25 cm for FR, 15 seconds for the TUG). Test-retest reliability between the screening and clinical administrations of the TUG was .56 for all participants (intra-class correlations), .50 for the cognitively unimpaired, and .56 for the cognitively impaired. Construct validity was substantial, and correlations between performance measures and self-report activities of daily living (ADL) measures ranged from .40 to .70. Compared with a global clinical measure of frailty, correlations were more modest (.38 to .60).

CONCLUSIONS

The FR and the TUG were not feasible tools in this study. The TUG showed poor test-retest reliability. Our data support the observation that subsequent studies of measurement instruments typically reveal lower performance than the original reports.

Prevalence and outcomes of vascular cognitive impairment. Vascular Cognitive Impairment Investigators of the Canadian Study of Health and Aging

OBJECTIVE

To assess the importance of vascular cognitive impairment and its three subgroups (cognitive impairment, no dementia; vascular dementia; and AD with a vascular component) to the prevalence and burden of cognitive impairment in elderly people.

BACKGROUND

Vascular lesions may produce a spectrum of cognitive changes. Omitting elderly patients whose cognitive impairment falls short of dementia (vascular cognitive impairment, no dementia) may give a falsely low indication of the prevalence and burden of disease. To test this proposition, we compared the rates of adverse outcomes for patients with no cognitive impairment, vascular cognitive impairment (and its subgroups), and probable AD.

METHODS

The Canadian Study of Health and Aging is a prospective cohort study of 10,253 randomly selected community-dwelling and institution-dwelling respondents aged 65 years or older. In the community, all participants (n = 9,008) were screened for cognitive impairment; those who screened positive and a sample of those who screened negative received a clinical assessment (n = 1,659). All patients living in institutions received a clinical assessment (n = 1,255). Participants were reassessed 5 years after the original survey.

RESULTS

Vascular cognitive impairment without dementia was the most prevalent form of vascular cognitive impairment among those aged 65 to 84 years. Rates of institutionalization and mortality for those with vascular cognitive impairment were significantly higher than those of people who had no cognitive impairment, and the mortality rate for patients with vascular cognitive impairment was similar to that of patients with AD.

CONCLUSIONS

Failure to consider vascular cognitive impairment without dementia underestimates the prevalence of impairment and the risk for adverse outcomes associated with vascular cognitive impairment.

Research criteria for subcortical vascular dementia in clinical trials

Vascular dementia (VaD) incorporate different vascular mechanisms and changes in the brain, and have different causes and clinical manifestations. Variation in defining the cognitive syndrome, in vascular etiologies, and allowable brain changes in current clinical definitions of VaD have resulted in variable estimates of prevalence, of groups of subjects, and of the types and distribution of putative causal brain lesions. Thus current criteria for VaD select an etiologically and clinically heterogeneous group. This definitional heterogeneity may have been a factor in "negative" clinical trials. An alternative for clinical drug trials is to focus on a more homogeneous group, such as those with subcortical (ischemic) VaD. This designation incorporates two small vessel clinical entities "Binswanger's disease" and "the lacunar state". It comprises small vessel disease as the primary vascular etiology, lacunar infarct(s) and ischaemic white matter lesions as the primary type of brain lesions, and subcortical location as the primary location of lesions. The subcortical clinical syndrome is the primary clinical manifestation, a definition which still requires additional empirical data. We expect that subcortical VaD show a more predictable clinical picture, natural history, outcome, and treatment responses. We propose a modification of the NINDS-AIREN criteria as a new research criteria for subcortical VaD.

Assessing the ADL functioning of persons with Alzheimer's disease: comparison of family informants' ratings and performance-based assessment findings

The activities of daily living (ADL) functioning of 26 subjects with Alzheimer's disease was measured using the Assessment of Motor and Process Skills (AMPS) and family informants' Older Americans Resources and Services (OARS) Activities of Daily Living (ADL) reports. Concordance with a clinician's ratings of subjects' level of ADL functioning was achieved for 77% of the subjects based on their AMPS ADL process ability measures and for 54% for the subjects based on their family informants' OARS ADL ratings. In cases of discordance, subjects' AMPS ADL process ability measures were just as likely to overestimate (11.5%) as to underestimate (11.5%) subjects' ADL functioning. In contrast, 46% of the informants overestimated their family members' ADL functioning, and this was more likely to occur when subjects' cognitive impairment was mild.

Validity of the confusion assessment method in detecting postoperative delirium in the elderly

In this prospective cohort of 71 elderly patients undergoing cardiac surgery, each subject was interviewed before and after surgery to detect incident delirium using the Confusion Assessment Method (CAM), the Mini-Mental State Examination (MMSE), the Clock Test, and a health record review. The first 41 were assessed by a physician and the remaining 30 by two study nurses. Delirium was then diagnosed by a physician using DSM-III-R criteria. Delirium was present in 23 subjects (32.4%). The sensitivity of the CAM differed significantly when administered by physicians compared to nurses (1.00 vs. .13). When standard cutoffs were used, neither the MMSE nor the Clock Test were found to be sensitive markers for delirium (.30 and .09, respectively). Recognition of delirium by charting was superior in nurses compared to physicians (.83 vs. .30). We conclude that the sensitivity of markers for delirium, such as the CAM and health record documentation, is dependent on the training background of the operator.

An individualized approach to outcome measurement in geriatric rehabilitation

BACKGROUND

The heterogeneity of health problems experienced by frail elderly patients makes it difficult to use a single standard measure to evaluate multiple outcomes of geriatric rehabilitation. Commonly, several measures are used, but an alternative is to use an individualized measure such as Goal Attainment Scaling (GAS). This study investigated the reliability, validity, and responsiveness of GAS as an outcome measure in geriatric rehabilitation.

METHODS

We studied 173 consecutive admissions (mean age 81; 77% female; mean length of stay 33 days) to a geriatric rehabilitation unit. Assessment instruments were completed at admission and discharge. Individualized treatment goals were identified for each patient by using GAS; standardized measures included self-rated health, a global clinical assessment, the Barthel Index, the OARS IADL scale, the Folstein Mini-Mental State Examination (MMSE), and the Nottingham Health Profile (NHP).

RESULTS

Mobility, future care arrangements, and functional impairment were the most commonly identified GAS goal areas. The interrater reliability of the GAS discharge score was 0.93. The GAS discharge score correlated strongly (r> or =0.50) with the standardized measures, except for self-rated health, the MMSE, and the NHP (r> or =0.31). GAS was more responsive to change than any of the standardized measures. The GAS score was used to derive receiver operating characteristic curves for other measures; this can provide insight into the interpretation of clinically important outcomes.

CONCLUSIONS

GAS appears to be a feasible, reliable, valid, and responsive approach to outcome measurement in geriatric rehabilitation.

Dynamics of cognitive aging: distinguishing functional age and disease from chronologic age in a population

This paper introduces a methodological approach to the dynamics of cognitively normal (i.e., successful) aging compared with aging accompanied by different types of cognitive impairment and dementia. Using secondary analysis of a national representative database (Canadian Study of Health and Aging, 1991-1992), the authors show that the occurrence of an adverse event (symptom, sign, or disease), or the accumulation of a number of events, may be modeled as a logistic function of chronologic age in a population. In the cognitively normal, a linear relation between the logarithm of the odds of events and chronologic age was present for the majority of symptoms and signs. This regression represents the accumulation of each sign in a cognitively successful, aging population. The authors then estimated which ages for this cognitively unimpaired group correspond to the odds of the occurrence of symptoms found for a cognitively impaired population at any given chronologic age. This may be regarded as functional age, based upon the accumulation of a particular functional deficit in the impaired population, analogous to the concept of frailty. The dynamics of aging are a complex process of accumulation of deficits (morbidity), whereby decline from some previously healthy level of synergistically associated symptoms and signs results in distinct patterns of disease and staging. The modeling of these dynamics takes us a step further toward the definition and refinement of disease and normal aging.

Factors associated with inconsistent diagnosis of dementia between physicians and neuropsychologists

OBJECTIVE

To explore reasons for discrepancy in the diagnosis of cognitive impairment between physicians and neuropsychologists.

DESIGN

Retrospective analysis of national survey data.

SETTING

Canadian Study of Health and Aging Phase 1, a national survey of community-dwelling and institutionalized older Canadians.

PARTICIPANTS

1879 subjects who completed all components of a clinical examination.

MEASUREMENTS

Data available to both disciplines (demographic data, functional status, Modified Mini-Mental State (3MS), schedule H of the Cambridge Mental Disorders of the Elderly Examination (CAMDEX)), results of the physician's history and physical examination, and results of a psychometric test battery. Subjects were classified as No Cognitive Impairment, Cognitive Impairment Not Dementia (CIND), and Dementia, the latter according to the criteria of the Diagnostic and Statistical Manual, 3rd Ed., Revised. Preliminary diagnoses by physicians and neuropsychologists were compared.

RESULTS

In univariate modeling, higher education increased consistency. Lower scores on the 3MS, depression reported in the CAMDEX, focal neurological signs, and all neuropsychological variables decreased agreement. In multivariate modeling, higher education and identification of long-term memory impairment by the neuropsychologist increased agreement; lower scores on the 3MS, depression reported on the CAMDEX, and identification of short-term memory impairment or constructional impairment led to disagreement. When the category of CIND was removed, kappa for agreement increased from 0.51 to 0.92.

CONCLUSIONS

Physicians and neuropsychologists have different, complementary approaches to the diagnosis of dementia, and a consensus approach should be used. The category of CIND requires elucidation. Identification of dementia in subjects with depression or low education is difficult, and new strategies are required.

Living alone with dementia

This report describes a population of individuals with dementia living alone in the community. Data were collected as part of the Canadian Study of Health and Aging (CSHA). We found that one third of the subjects in the CSHA sample with a dementia residing in the community lived alone. Whether their identified informal caregiver had thought about institutionalization was an important factor in actual short-term (2-year) institutionalization and appeared to be influenced by living arrangements. Caregivers of those living alone provided less hands-on assistance, experienced less burden, and were less likely to be depressed than those living with the demented person, but were more likely to have considered institutionalization. Presumably, this was driven by concerns about safety and support. How to support the growing numbers of individuals with dementia living alone in the community will be a significant challenge. Copyrightz1999S.KargerAG,Basel

Outcome measures for the study of activities of daily living in vascular dementia

Decline in functional abilities is a major component of the dementia syndrome. The definition of dementia in the International Classification of Diseases (10th rev.) requires a cognitive impairment sufficient to impair personal activities of daily living (ADL). The Diagnostic and Statistical Manual of Mental Disorders (4th ed.) also requires cognitive deficits sufficiently severe to cause impairment in occupational or social functioning and must represent a decline from a higher level of functioning. However, the term disability is more appropriate than impairment to describe a loss in activities, as opposed to a loss of elementary functions, and is consistent with World Health Organization definitions of impairment, disability, and handicap. There is no doubt that ADL outcomes are required in therapeutic drug studies on vascular dementia, and there is a good rationale and some evidence for the use of ADL scales developed for therapeutic research in Alzheimer disease, favoring scales devoid of items sensitive to physical disabilities. Similarly, ADL-related clinical milestones could be used for longer-term studies aiming predominantly at slowing progression of disease in both early and later stages of dementia. Slower decline in ADL and delay in reaching ADL-related clinical milestones should be considered as valid outcomes by regulatory bodies in the process of dementia drug approval.

Imaging of static brain lesions in vascular dementia: implications for clinical trials

Vascular dementia (VaD) relates to different vascular mechanisms and changes in the brain and has different causes and clinical manifestations, reflecting complex interactions between vascular etiologies, changes in the brain, host factors, and cognition. Critical elements to the concept and diagnosis of VaD are defining the vascular causes, the vascular etiologies, and changes in the brain. Verifying the relation between brain lesions and cognition (i.e., the extent to which brain changes cause, compound, or coexist with cognitive impairment) and establishing the types, extent, side, site, and tempo of brain lesions that relate to incident cognitive impairment are major diagnostic challenges. Previous work on interactions between brain lesion and cognition in to cerebrovascular disease (CVD) have shown variation in the definitions and measures of cognitive impairment, in the techniques and methods used to reveal different brain changes, and in the selection of patient populations. Furthermore, small sample sizes and the absence of multivariate statistics have been design limitations. Accordingly, the different sets of criteria used and methods applied identify different numbers and clusters of subjects and different distribution of brain changes. Furthermore, this heterogeneity is reflected in variation in natural history such as the rate of progression of decline in different cognitive domains over time. All these factors have hampered optimal designs of clinical drug trials. A summary of generalizations regarding lesion and cognition interaction in VaD can be made. (1) Not a single feature, but a combination of infarct features--extent and type of white matter lesions (WMLs), degree and site of atrophy, and host factor characteristics--constitues correlates of VaD. (2) Infarct features favoring VaD include bilaterality, multiplicity (>1), location in the dominant hemisphere, and location in the limbic structures (fronto- and mediolimbic). (3) WML features favoring VaD are extensive WMLs (extensive periventricular WMLs and confluent to extensive WMLs in the deep WM). (4) It is doubtful that only a single small lesion could provide imaging evidence for a diagnosis of VaD. (5) Absence of CVD lesions on computed tomography or magnetic resonance imaging is strong evidence against a diagnosis of VaD. In forthcoming protocols on CVD-associated cognitive impairment, the following brain imaging features should be specified: detailed characterization of brain changes; use of possible predefined subtypes based on brain imaging; use of rating of vascular burden; defining the type and extent of WMLs favoring a diagnosis of VaD; defining the extent of medial temporal lobe atrophy disfavoring a diagnosis of VaD; and technical harmonization of methods of scanning and analysis.

The risk of dementia and death after delirium

BACKGROUND

delirium is common and is associated with many adverse short-term consequences.

OBJECTIVES

to examine the relationship between an episode of delirium and subsequent dementia and death over 3 years.

DESIGN

prospective cohort study.

SETTING

patients (n = 203) were aged 65 years or older at baseline and survivors of the index admission.

METHODS

Using a standard assessment of cognitive function, we followed 38 inpatients diagnosed with delirium (22 with delirium and dementia, 16 with delirium only) and 148 patients with no delirium or dementia, for a median of 32.5 months. Follow-up was by personal interviews, supplemented by standardized clinical examinations. We calculated the incidence and odds of dementia and the incidence and hazard ratio for death, with adjustment for potential confounders.

RESULTS

The incidence of dementia was 5.6% per year over 3 years for those without delirium and 18.1% per year for those with delirium. The unadjusted relative risk of dementia for those with delirium was 3.23 (95% confidence interval 1.86-5.63). The adjusted relative risk of death also increased (1.80; 1.11-2.92), while the median survival time was significantly shorter in those with (510 days; 433-587) than in those without delirium (1122 days; 922-1322).

CONCLUSION

delirium appears to be an important marker of risk for dementia and death, even in older people without prior cognitive or functional impairment.

Subtypes of vascular dementia

The challenge of describing subgroups is particularly important in vascular dementia, which, in contrast to more stereotypic processes affecting cognitive function, is better thought of as several syndromes rather than as a disease. Many current diagnostic descriptions lack a strong empiric basis. Some of the categories now in use suffer from a priori assumptions about causality and pattern associations, which themselves have not been validated. The so-called mixed dementia syndrome may have been underrepresented in our estimation of dementia subtypes, in comparison with so-called pure vascular causes. Within the vascular syndrome, whether seen in isolation or in combination with other causes of dementia, the relative contributions of white matter changes as compared with multiple cortical strokes needs to be clarified. It remains a matter of controversy as to whether prolonged or chronic intermittent cerebral ischemia is a statistically important part of the dementia. The variable relation between clinical presentation and neuroimaging localization has important consequences for understanding the pathophysiology of cognitive impairment arising from vascular causes. Recent data also suggest that we should focus away from both the Alzheimer disease model of dementia and the multi-infarct model of vascular dementia. There are important opportunities available to clinicians from many disciplines to collaborate in precise clinical descriptions of large numbers of patients to advance our understanding of the spectrum of vascular cognitive impairment.