August 29, 2005
Subtle signs of memory loss may appear in men and women up to 10 years before Alzheimer's disease is officially diagnosed, Swedish researchers report. The findings suggest that mental deficits are common in the years preceding the onset of Alzheimer's, an illness that afflicts some 4.5 million Americans. Doctors hope that the findings could one day lead to diagnostic tests that identify impending Alzheimer's at a very early stage and lead to effective treatments that stem the downward spiral of memory loss that characterizes the disease.
Psychologists at the Karolinska Institute in Stockholm and the Stockholm Gerontology Research Center combed through data from 47 scientific studies involving more than 1,200 older men and women who went on to develop Alzheimer's disease. Results on memory and other cognitive exams over a 10-year-plus period were compared with those from more than 9,000 seniors of similar age who remained mentally intact.
The researchers found that up to 10 years preceding a diagnosis of Alzheimer's disease, people tended to show lapses in recall and took a little longer to solve problems or puzzles. They also showed problems in "executive" brain functions, or the ability to plan ahead and multitask. The researchers noted more modest problems relating to verbal ability, visual and spatial skills, and paying attention.
These memory problems were very subtle, however, and many of those who later developed Alzheimer's disease could carry out their daily activities just fine. For example, they might forget what they had for breakfast that morning, but they were still able to keep appointments and balance checkbooks. Although memory lapses and "senior moments" are a normal part of growing older, the researchers found that the problems were more pronounced in those who ended up with Alzheimer's.
The study traced other interesting patterns as well. People who progressed to Alzheimer's quickly, in three years or less, tended to be more mentally impaired in the years before their diagnosis. Those who were diagnosed with Alzheimer's at a younger age also tended to have more severe symptoms, perhaps because of more serious defects in the brain, the researchers speculate. The findings appeared in the July issue of Neuropsychology, a research journal published by the American Psychological Association.
The data support an emerging consensus among doctors that most people show subtle mental and memory deficits years before Alzheimer's disease is diagnosed. It is important to recognize, however, that mental decline can be caused by many other conditions and circumstances unrelated to Alzheimer's.
The findings agree with recent studies showing that the brain begins to show signs of physical defects in the hippocampus and other areas years before Alzheimer's is diagnosed. The findings are also consistent with emerging research suggesting that various mental and physical symptoms may be early harbingers of Alzheimer's disease.
Earlier this year, for example, researchers from the Howard Hughes Medical Institute found that certain shape changes in the network of nerves that crisscross the brain may play a role very early in the course of Alzheimer's disease, contributing to progressive memory loss, confusion, and other telltale symptoms. This observation is not yet useful for predicting Alzheimer's risk, however, because the test is not likely to be performed on live patients.
Other studies indicate that physical symptoms, such as weight loss, may appear years before the severe memory loss of Alzheimer's becomes apparent. However, weight loss can be caused by many conditions unrelated to Alzheimer's.
Doctors hope that taken together, these factors, combined with numerous other observations, may allow them to predict who is most likely to get Alzheimer's disease. This information will be most useful when there are effective drugs available to treat and prevent Alzheimer's.
Scientists emphasize that further research is needed to confirm these findings and to learn more about what goes wrong in the brain during Alzheimer's disease. Still, doctors hope that early diagnosis could one day lead to new drugs and therapies that help preserve or restore memory and brain function. They may also lead to improved diagnostic tests that may detect Alzheimer's in its earliest stages.
The Fisher Center for Alzheimer's Research Foundation has played a leading role in funding research into Alzheimer's disease and the brain. Only through continued research can we learn more about what goes wrong in Alzheimer's disease, and what we can do to treat and cure it. To learn more, visit www.ALZinfo.org.
Lars Bäckman, PhD, Sari Jones, PhD, Anna-Karin Berger, PhD, and Erika Jonsson Laukka. PhD: "Cognitive impairment in preclinical Alzheimer's disease: A meta-analysis." Neuropsychology, Volume 19, No. 4m July 2005.