alzheimers-diagnosis

Alzheimer's disease symptoms more subtle in people over 80

September, 2011

A new study shows that, among the very old, it’s harder to distinguish between normal brain atrophy and cognitive impairment and that indicative of Alzheimer’s.

A study involving 105 people with Alzheimer's disease and 125 healthy older adults has compared cognitive function and brain shrinkage in those aged 60-75 and those aged 80+.

It was found that the association between brain atrophy and cognitive impairment typically found in those with Alzheimer’s disease was less evident in the older group. This is partly because of the level of brain atrophy in healthy controls in that age group — there was less difference between the healthy controls and those with Alzheimer’s. Additionally, when compared to their healthy counterparts, executive function, immediate memory and attention/processing speed were less abnormal in the older group than they were in the younger group.

The finding suggests that mild Alzheimer’s in the very old may go undetected, and emphasize the importance of taking age into account when interpreting test performance and brain measures.

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Diagnosis and prevalence of dementia & MCI — recent reports

August, 2011

Several recent reports point to the need for GPs to be better informed about the initial symptoms of dementia and mild cognitive impairment.

Functional impairment good indicator of mild cognitive impairment

Evaluation of 816 older adults, of whom 229 had no cognitive problems, 394 had a diagnosis of amnestic mild cognitive impairment, and 193 had a diagnosis of mild Alzheimer’s, has revealed that most of those with aMCI (72%) or AD (97%) had trouble with at least one type of function on the Pfeffer Functional Activities Questionnaire. Only 8% of controls had any difficulty. In both impaired groups, those who had the most difficulty functioning also tended to score worse on cognition tests, have smaller hippocampal volumes, and carry the APOe4 gene.

Two of the ten items in the questionnaire were specific in differentiating the control group from the impaired groups. Those items concerned "remembering appointments, family occasions, holidays, and medications” and "assembling tax records, business affairs, or other papers." Only 34% of those with aMCI and 3.6% of those with AD had no difficulty with these items.

The findings suggest that even mild disruptions in daily functioning may be an important clinical indicator of disease.

Early-onset Alzheimer’s poorly diagnosed when initial symptoms aren’t memory related

Post-mortem analysis of 40 people diagnosed  with early-onset Alzheimer’s has revealed that about 38% experienced initial symptoms other than memory problems, such as behavior, vision or language problems and a decline in executive function, or the ability to carry out tasks. Of these, 53% were incorrectly diagnosed when first seen by a doctor, compared to 4% of those who had memory problems. Of those with unusual initial symptoms, 47% were still incorrectly diagnosed at the time of their death.

The mean age at onset was 54.5 years (range 46-60). The average duration of the disease was 11 years, with an average diagnostic delay of 3 years.

GPs misidentify and fail to identify early dementia and MCI

A review of 30 studies involving 15,277 people seen in primary care for cognitive disorders, has found that while GPs managed to identify eight out of ten people with moderate to severe dementia, they only identified 45% of those with early dementia and mild cognitive impairment. Moreover, they were very poor at recording such diagnoses. Thus, though they recognized 45% of the MCI cases, they only recorded 11% of these cases in their medical notes. Although they identified 73% of people with dementia, they made correct annotations in medical records in only 38% of cases.

But the problem is not simply one of failing to diagnose — they were even more likely to misidentify dementia, and this was particularly true for those with depression or hearing problems.

The findings point to the need for more widespread use of simple cognitive screening tests.

Prevalence of dementia & MCI in 'oldest old' women

Data from 1,299 women enrolled in the Women Cognitive Impairment Study of Exceptional Aging suggests that the incidence of dementia almost doubles with every 5 years of age and prevalence rises from approximately 2-3% in those 65 to 75 years to 35% in those 85+.

Among those with mild cognitive impairment, amnestic multiple domain was most common (34%), followed by non-amnestic single domain (29%). Amnestic single domain (affecting only one type of cognitive function, including memory difficulty) affected 22%.

Alzheimer's disease and mixed dementia accounted for nearly 80% of dementia cases, and vascular dementia for 12.1%.

Those with dementia tended to be older, less likely to have completed high school, more likely to have reported depression, a history of stroke, and to have the APOEe4 gene.

The women in the study had an average age of 88.2 years and 27% were older than 90. 41% had clinical cognitive impairment (17.8% with dementia and 23.2% with mild cognitive impairment).

The high prevalence of cognitive impairment in this age group points to the importance of screening for cognitive disorders, particularly among high-risk groups.

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Alzheimer's diagnostic guidelines updated

June, 2011

Updated clinical guidelines now cover three distinct stages of Alzheimer's disease.

For the first time in 27 years, clinical diagnostic criteria for Alzheimer's disease dementia have been revised, and research guidelines updated. They mark a major change in how experts think about and study Alzheimer's disease.

The updated guidelines now cover three distinct stages of Alzheimer's disease:

  • Preclinical – is currently relevant only for research. It describes the use of biomarkers that may precede the development of Alzheimer’s.
  • Mild Cognitive Impairment– Current biomarkers include elevated levels of tau or decreased levels of beta-amyloid in the cerebrospinal fluid, reduced glucose uptake in the brain, and atrophy of certain brain regions. Primarily for researchers, these may be used in specialized clinical settings.
  • Alzheimer's Dementia – Criteria outline ways clinicians should approach evaluating causes and progression of cognitive decline, and expand the concept of Alzheimer's dementia beyond memory loss to other aspects of cognition, such as word-finding, vision/spatial issues, and impaired reasoning or judgment.

The criteria are available at http://www.alzheimersanddementia.org/content/ncg

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Review confirms early diagnosis tool

February, 2010

A comprehensive survey confirms the value of an early diagnostic tool, and provides strong evidence for the central importance of amyloid-beta protein plaques in the development of Alzheimer’s.

A survey of more than 100 studies involving PIB-PET, a diagnostic tool that involves injecting a radiotracer called Pittsburgh compound B into the brain via the bloodstream, and imaging the brain with positron emission tomography (PET), has confirmed its sensitivity in detecting amyloid-beta protein plaques. The tool is not yet commercially available. The study also provides strong evidence supporting the theory that accumulation of amyloid-beta protein plaques in the brain is central to the development of Alzheimer’s. The findings, that amyloid deposits appear to reach a plateau early in the disease course, may explain why Alzheimer's patients have not responded to promising experimental drugs that target amyloid. It may be that they are being administered too late.

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New test to diagnose early stage Alzheimer's disease

March, 2010

A new test has been developed that measures amyloid-beta oligomers in the cerebrospinal fluid, promising a reliable means of early diagnosis.

A new test has been developed that measures amyloid-beta oligomers in the cerebrospinal fluid, promising a reliable means of early diagnosis. In a comparison of patients with Alzheimer’s, patients with MCI that later developed into Alzheimer’s, and controls, levels of these protein fragments directly correlated with Alzheimer’s, and was more accurate than levels of the more usual amyloid plaques.

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