Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

More sensitive test norms better predict who might develop Alzheimer’s disease

05.01.2004


Higher cutoffs led to more accurate identification of high-functioning



Diagnosticians would do well to raise the bar when testing high-functioning people for pre-clinical signs of Alzheimer’s disease, according to a new study. Higher test cutoffs, rather than the standard group average, more accurately predicted how many highly intelligent people would deteriorate over time. This finding is reported in the January issue of Neuropsychology, which is published by the American Psychological Association (APA).

Early diagnosis of Alzheimer’s has taken on growing importance, given new medical and psychological interventions that can slow (but not stop) the course of the disease. In addition, highly intelligent people have been found, on average, to show clinical signs of Alzheimer’s later than the general population. Once they do, they decline much faster. Thought to reflect their greater mental reserves, this different pattern may call for a different approach to diagnosis.


Says lead author Dorene Rentz, PsyD, "Highly intelligent elders are often told their memory changes are typical of normal aging when they are not. As a result, they would miss the advantages of disease-modifying medications when they become available."

Rentz, of Brigham and Women’s Hospital’s Department of Neurology and Harvard Medical School, led her co-authors in a study of 42 older people with IQ’s of 120 or more, drawn from a longitudinal study of aging and Alzheimer’s Disease. Rentz and her colleagues analyzed participant performance on measures of cognitive ability, such as word generation, memory and visuospatial processing, with scores gathered at the start of the study and three-and-a-half years later. Then, they asked which of two different test norms forecast problems: The standard norm, derived from a large cross-section of the population, or an adjusted high-IQ norm that measured changes against the individual’s higher ability level?

The raised cutoffs worked better. For memory scores obtained at baseline, raised cutoffs predicted that 11 of the 42 individuals were at risk for future decline – compared with standard cutoffs, which indicated they were normal. But, what’s normal for people of average IQ isn’t normal for people of higher IQ: True to the former prediction, three and a half years later, nine of those 11 people had declined. Six of those went on to develop mild cognitive impairment (MCI), a transitional illness from normal aging to a dementia (of which one type is Alzheimer’s). Five of these individuals have since received a diagnosis of Alzheimer’s disease, two years after this study was submitted.

"With standard norms, people with higher levels of ability would be classified as normal for up to three years before they began demonstrating a decline on standardized tests," says Rentz. "In this case, they could be at risk for not receiving early treatment intervention."

The statistical approach was simple. High-IQ people were scored against an average that was "normal" for them, proportionately higher than the cross-sectional average of 100. Scores were considered abnormal if, according to standard practice, they were 1.5 standard deviations or more below the (adjusted) norm.

Rentz and her co-authors believe that by the same reasoning, adjusted norms could help people at the other end of the scale. "People with below-average intelligence have the potential for being misdiagnosed as ’demented’ when they are not, because they score below the normative cutoffs," explains Rentz. Adjusting norms to match the ability level of the person being evaluated, she believes, could have the greatest predictive power in detecting the early signs of an incipient Alzheimer’s-type dementia.

Rentz points out that for women, adjusting for IQ may be particularly useful compared with traditional adjustments for education. "Education-based methods often underestimate ability in women who did not have the same educational advantages as men, particularly in this aged cohort," she says.

The authors also report that IQ-adjusted norms might help to control for some inaccuracies that have filtered into normative data, as these norms were derived from cross-sectional populations who might not have been adequately screened for preclinical Alzheimer’s disease. Because it could take a long time to develop new databases from longitudinal studies, the authors say that the "use of an IQ-adjusted method may provide a temporary solution for clinicians and research investigators evaluating older highly intelligent individuals at risk for Alzheimer’s disease."


Article: "Use of IQ-Adjusted Norms to Predict Progressive Cognitive Decline in Highly Intelligent Older Individuals," Dorene M. Rentz, PsyD, Brigham and Women’s Hospital and Harvard Medical School; Terri J. Huh, MA, University of Massachusetts at Boston; and Robert R. Faust, B.A., Andrew E. Budson, MD, Leonard F.M. Scinto, PhD, Reisa A. Sperling, MD, and Kirk R. Daffner, MD, all of Brigham and Women’s Hospital’s Department of Neurology and Harvard Medical School; Neuropsychology, Vol. 18, No. 1.

(Full text of the article is available from the APA Public Affairs Office)

Dorene Rentz can be reached by email at drentz@partners.org or by phone at 617-732-8235. She can also be reached through a publicist, Melanie Franco, 617-534-1605 or mfranco1@partners.org. The American Psychological Association (APA), in Washington, DC, is the largest scientific and professional organization representing psychology in the United States and is the world’s largest association of psychologists. APA’s membership includes more than 150,000 researchers, educators, clinicians, consultants and students. Through its divisions in 53 subfields of psychology and affiliations with 60 state, territorial and Canadian provincial associations, APA works to advance psychology as a science, as a profession and as a means of promoting human welfare.

Pam Willenz | EurekAlert!
Further information:
http://www.apa.org/

More articles from Health and Medicine:

nachricht Correct connections are crucial
26.06.2017 | Charité - Universitätsmedizin Berlin

nachricht One gene closer to regenerative therapy for muscular disorders
01.06.2017 | Cincinnati Children's Hospital Medical Center

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Touch Displays WAY-AX and WAY-DX by WayCon

27.06.2017 | Power and Electrical Engineering

Drones that drive

27.06.2017 | Information Technology

Ultra-compact phase modulators based on graphene plasmons

27.06.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>