Alzheimer's disease looks different in people over 80

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Medscape Today

Alzheimer's disease (AD) may be more difficult to detect in people older than 80 years, suggest results of a new study, because disease presentation may be different than that seen in the larger population of patients.

"The typical pattern of AD-related cognitive and morphometric changes seen in the young old appear to be less salient in the very old," first author Nikki H. Stricker, PhD, from the Veterans Affairs Boston Healthcare System and the Department of Psychiatry, Boston University School of Medicine, Boston, Massachusetts, and colleagues report.

"Thus, mild cases of AD in the very old may go undetected if one expects to see the prototypical pattern and severity of cognitive or brain changes that occur in the young old with AD," they conclude.

This study highlights "the importance of paying attention to age when reviewing cognitive test performances and in reviewing other possible biomarkers of Alzheimer's disease such as neuroimaging scans," coauthor Mark W. Bondi, PhD, from the Psychology Service, Veterans Affairs San Diego Healthcare System, San Diego, California, noted in comments to Medscape Medical News.

Their results are published online August 10 in Neurology.

Signs, Symptoms More Subtle in 80-Plus Group

The researchers compared hippocampal volume and cortical gray matter thickness in areas known to be affected by AD in 105 patients with AD and 125 healthy control participants. Participants between 60 and 75 years old made up the "young-old" group, whereas those 80 years and older made up the "very-old" group. Among the 105 participants with AD, 64 were young-old, and 41 were very-old.

Brain morphometric and cognitive scores of the patients with AD were standardized to their respective age-appropriate healthy control subgroup and then compared, the researchers explain.

In the very-old, compared with the young-old, there was less severe cortical thinning in the left posterior cingulate cortex, right lateral temporal cortex, and bilateral parietal cortex, as well as in overall cortical thickness.

This finding is, in part, because these brain areas decrease in thickness as a result of aging. Therefore, there are fewer differences between the healthy very-old brain and the very-old brain with AD, the researchers point out.

"Our results indicate that overlap between normal and AD-related brain changes seen on magnetic resonance imaging (MRI) scans is greater in the very-old than in the young-old," Dr. Bondi said. "For example, the typical pattern of brain changes seen in an 85-year-old person with AD is less salient than in a 70-year old person with AD."

Similarly, several cognitive domains, including executive function, immediate memory, and attention/processing speed, were less abnormal in the very-old patients with AD relative to their young-old peers.

Broad Clinical Implications

"Clarification of how the presentation of AD changes with age may enhance our ability to detect early AD in the very-old, one of the fastest growing segments of the population," Dr. Bondi commented.

"Enhanced detection will be crucial for early application of interventions that may slow the disease process, thus preserving cognitive status, functional independence, and quality of life," he added.

Reached for comment, Rhoda Au, PhD, from the Department of Neurology, Boston University School of Medicine in Boston, Massachusetts, said "the most important broader implications" of this study are "its recognition of the developmental continuum extending to the very last years of life (and) that the elderly population cannot be characterized as a single subset population."

Dr. Au was not involved in the study but authored a linked commentary in the journal.

"As more and more people live into the 8th and 9th decades and beyond, the diagnostic and treatment practices applied to the younger old may not apply or work as effectively with the oldest old," she told Medscape Medical News.

The study was supported primarily by the National Institutes of Health (NIH) and the Dana Foundation. Dr. Stricker receives or has received research support from the Rosalind and Arthur Gilbert Foundation/American Federation for Aging Research and the NIH. Dr. Bondi serves as an associate editor for the Journal of the International Neuropsychological Society and receives research support from the Alzheimer's Association and the NIH. A complete list of author disclosures is listed in the original article. Dr. Au receives research support from the National Institute on Aging, the National Institute of Neurological Disorders and Stroke, and the Fogarty International Center.