The differentiation of major depression from dementia of the Alzheimer type using within-subject neuropsychological discrepancy analysis

Screening for mild cognitive impairment: a systematic review

OBJECTIVE

Patients with mild cognitive impairment account for a significant number of referrals to old age psychiatry services and specialist memory clinics. The cognitive evaluation of such patients is commonly restricted to brief dementia screens, with no consideration to their suitability for assessing MCI. Here, we review the utility of such cognitive screens for MCI and provide an overview of validated instruments.

METHODS

We identified papers published after Petersen and colleagues 1999 MCI criteria (Petersen et al., 1999) and examining face-to-face cognitive screening for MCI from publication databases using combinations of the search terms 'mild cognitive impairment' and 'cognitive screening'. We also combined the former search with the names of 39 screening tests recently identified in a relevant review (Cullen et al., 2007).

RESULTS

Fifteen cognitive screening instruments were identified, 11 cover a restricted range of cognitive domains. High sensitivity and specificity for MCI relative to healthy controls were reported for two comprehensive and two noncomprehensive screening instruments, adequate test-retest and inter-rater reliability for only one of these. With the exception of three studies, sample sizes were universally small (i.e. n </= 100), and prognostic values were reported for only two of the identified 15 screening measures. Sensitivities of the full domain measures were universally high, but information about their specificity against psychiatric and non-progressive neurological conditions and predictive validity is lacking.

CONCLUSION

Several cognitive screening instruments afford the clinician the ability to detect MCI, early AD, and in some cases non-AD dementia, but they cannot currently be used to make reliable inferences about the course and eventual outcome of MCI.

Screening for cognitive impairment: a triage for outpatient care

The current increase in aged individuals in number and proportion of the general population warrants dependable strategies to improve early detection of cognitive impairment. It was the goal of the present study to develop a triage for bedside testing and outpatient services. In a prospective clinical cohort study at the outpatient Memory Clinic, University of Ulm, Germany, 232 subjects were diagnosed with Alzheimer's disease [AD; NINCDS-ADRDA criteria; n = 66; age 65.9 +/- 7.3 years (mean +/- SD); Mini Mental State Examination (MMSE) score 23.4 +/- 4.1], mild cognitive impairment (MCI; criteria of Petersen et al.; n = 48; age 66.4 +/- 7.1 years; MMSE score 28.3 +/- 1.5), and major depressive disorder (DSM-IV criteria; n = 61; age 63.4 +/- 8.0 years; MMSE score 28.6 +/- 1.6). Diagnosis was secured with extensive neuropsychological, clinical, radiological, and laboratory investigations. Six brief screening tests including the Memory Impairment Screen (MIS), Letter Sorting Test (LST), Verbal Fluency (VF), and Clock Drawing Test (CDT) were assessed independently from the diagnostic procedure. We compared single items and composite scores. LST yielded a diagnostic accuracy of 0.81 and 0.62 for AD and MCI patients versus controls, respectively. With the MIS, diagnostic accuracy was 0.89 and 0.71, respectively. With a combination of LST, MIS, VF, and CDT, a sensitivity for AD and MCI patients of 1.00 and 0.83 was achieved. Thus, single-item screening (e.g. LST, VF) taking little more than 1 min and suitable for bedside testing or brief screening in the general practitioner's office yields diagnostic accuracy comparable to standard laboratory tests for other diseases. A composite of screening tests suitable for application in general outpatient care in neurological and psychiatric services reliably detects patients with AD and MCI.

The use of word-reading to estimate "premorbid" ability in cognitive domains other than intelligence

Diagnostic neuropsychological assessment requires the clinician to estimate a patient's premorbid abilities. Word reading tests, such as the National Adult Reading Test-Revised (NART-R), provide reasonably accurate estimates of premorbid IQ, but their capacity to benchmark other premorbid cognitive abilities remains unclear. In this extension of an earlier report, we administered the NART-R, an abbreviated Wechsler Adult Intelligence Scale (WAIS-R or WAIS-III), and 26 other cognitive measures to 322 reasonably healthy adults. While NART-R performance correlated robustly (rs > or = .72) with concurrent Verbal and Full Scale IQ, its correlation with all other cognitive measures was significantly lower. Thus, while it is appealing to use word reading as a proxy for premorbid functioning in other cognitive domains, the NART-R has limited utility for this because it does not predict current performance on other cognitive tests as well as it predicts IQ in healthy adults.

Depressive symptoms increase the likelihood of cognitive impairment in elderly people with subclinical Alzheimer pathology

The objective of this study was to investigate whether the presence of depressive symptoms influences the clinical expression of Alzheimer's pathology. We have analysed the relationships between the severity of Alzheimer's pathology and cognitive decline in two patient groups defined by the presence or absence of depressive symptoms. The study included 89 subjects who participated in a longitudinal research programme prior to death, underwent post-mortem examination and were found to have only Alzheimer-type pathology in their brains, ranging in severity from the entorhinal to neocortical stages. Our results indicate that depressive symptoms did not influence cognition in the early (entorhinal) stages of Alzheimer's disease (AD; where cognition was good regardless of whether or not there was evidence for depressive symptoms) or in the late (neocortical) stages (where cognition was poor regardless of whether or not there was evidence for depression). However, in the intermediate (limbic) stages, patients with depressive symptoms had significantly worse cognitive performance (mean CAMCOG of 32) than those who did not (mean CAMCOG of 73). We conclude that depressive symptoms may contribute to the cognitive decline of AD patients in that pathology, that would be otherwise silent, becomes clinically apparent. Therefore, a multiple diagnosis of early AD and depression should be more widely considered in elderly persons presenting with mild cognitive decline and depression. Treating the depressive symptoms would benefit the patient, but the cognitive improvement may not indicate that AD is absent.

Subjective memory complaints: objective neural markers in patients with Alzheimer's disease and major depressive disorder

Patients with probable Alzheimer's disease and depressive patients frequently present with subjective memory complaints. Objective distinction of underlying neuronal substrate malfunction and early cross-sectional differential diagnosis have been elusive thus far. We used repetitive learning and free recall of abstract geometric patterns during functional magnetic resonance imaging to assess episodic memory in older subjects (ages 56-64 years) who sought first-time medical attention with subjective memory complaints and were diagnosed with probable Alzheimer's disease (NINCDS-ADRDA criteria; ages 51-67 years) or major depressive disorder (DSM-IV; ages 50-65 years). Contrasting healthy seniors or depressive patients with Alzheimer's disease patients revealed superiority of hippocampal activation. Contrasting Alzheimer's disease patients with seniors showed bilateral prefrontal activity as a correlate of futile compensation of episodic memory failure. Contrasting patients who had major depressive disorder with seniors or patients who had Alzheimer's disease showed bilateral activation of the orbitofrontal cortex and the anterior cingulate. Subjective memory complaints may be classified objectively and very early with functional magnetic resonance imaging of episodic memory in groups of patients with Alzheimer's disease and depressive syndrome. This may facilitate drug trials with evaluation of specific treatments, but further studies will be needed to establish the differential diagnosis for the individual patient.

Distinguishing depression from dementia in later life: a pilot study employing the Emotional Stroop task

OBJECTIVES

In later life, cognitive impairment is common in depression often making it difficult to distinguish a dementing illness from depression. We examined whether people with depression could be differentiated from those with dementia on their performance on a task that examines attentional bias to depression related material.

METHODS

Twelve older adults who fulfilled DSM-IV criteria for major depression were compared with 12 people with Alzheimer's Disease (AD) and 12 age matched controls on a test of cognitive biases: the Emotional Stroop task. In this task participants were presented with words written in different coloured inks, and they had to name the colour the word was written in. Four types of material were presented-neutral, positive, and negative emotion words as well as a condition of meaningless symbols.

RESULTS

People with depression and those with AD were both slower than the controls on the task generally. However, the depressed group alone showed a statistically significant and specific increase in response time when colour naming the negative emotion words. The other two groups did not demonstrate such a pattern and colour named neutral, positive and negative words equally quickly.

CONCLUSIONS

The biased processing of depression related material may have a valuable role in distinguishing depression from dementia in later life. Although the Emotional Stroop in its present form is not sufficient for such a purpose. Furthermore, the demonstration that older adults with depression exhibit such biases helps provide a theoretical basis for the application of cognitive behavioural treatments with older adults.

Differential diagnosis of the major progressive dementias and depression in middle and late adulthood: a summary of the literature of the early 1990s

There is a preponderance of research on the neuropsychology of the various dementias. There are also direct comparisons between two or more dementias available in the literature. This paper sought to summarize the most recent literature, primarily from 1990 through mid-1996, including recent reviews of the literature from previous decades. The purpose was to provide, in one location, a summary of neuropsychological (i.e., cognitive, motor, and psychiatric) characteristics of major noninfectious, progressive dementias and depression of middle and late adulthood. It is hoped that this review, particularly a summary table provided, will serve as a guide in the differential diagnosis of the dementias by clinicians. In addition to Alzheimer's disease, vascular dementias, Parkinson's disease, Lewy body dementia, Huntington's disease, and frontal lobe dementia, the impact of depression on cognitive functioning is covered given the frequency with which neuropsychologists are asked to differentiate depression from primary dementia.

Depression and memory in the elderly: a meta-analysis

A meta-analysis (N = 40) of the effects of depression on memory in the elderly (sample mean age > or = 55 years) examined variables potentially accounting for divergent findings in the literature. The distribution of effects was bimodal and the effect sizes were heterogeneous. Compared to controls, groups containing unipolar subjects only were significantly less impaired than were mixed unipolar-bipolar; five of six studies mixing depression subtype were associated with the more negative mode. Samples containing younger depressed subjects (< 45 years) were significantly more impaired and were associated with the more negative mode. Significant group differences were found between studies matching their comparison groups reasonably well on years of education and those that did not. Thoroughness of dementia screening yielded no group differences. Although correlated observations precluded significance tests, larger effects were found for (1) figural (vs. verbal) memory; (2) delayed (vs. immediate) memory; and (3) recognition (vs. free recall and incidental or cued recall; incidental and cued recall effects were nearly identical). Similar effects were found for composite memory scores versus constituent and for various presentation paradigms (e.g., single presentation, selective reminding). Effect sizes for these categories were in the moderate range. Difficulties synthesizing this literature are discussed as are suggested remedies and directions for future research.

Neuropsychological and neuroimaging evidence for the involvement of the frontal lobes in depression

The onset and reversibility of major depression is likely to be explained by diffuse neuromodulatory mechanisms rather than permanent abnormalities of connectivity and neurotransmission. However, the expression of mood state appears to involve fronto-striatal mechanisms. Lesions of the ventral frontal cortex give rise to profound modification of affect and behaviour not explained by effects on current intellectual function. These may represent the most extreme possible disturbances of emotional experience. Neuropsychological testing in major depression shows evidence of slowing in motor and cognitive domains with additional prominent effects on mnemonic function most marked in the elderly. Structural imaging with X-ray computed tomography or magnetic resonance imaging in older patients with major depression shows evidence of structural abnormality compared with controls. These findings are not highly localizing but they tend to confirm the role of cognitive impairment as an important age-related risk factor for major depression. Perfusion or metabolic imaging reflects both reversible changes in function and permanent loss of active neurones. The usual finding has been reductions in anterior brain structures in major depression. Hypoperfusion tends to be greatest in frontal, temporal and parietal areas and most extensive in older (male) patients; high Hamilton scores tend to be associated with reduced uptake. There have also been correlations in the cingulate cortex between increased perfusion and other aspects of the mental state. In general, reductions in frontal areas may be more likely in patients with impoverished mental states. The more prominent impairments of memory are likely to be associated with the finding of impaired temporal function or with a more diffuse failure of neuromodulation.