November 23, 2009
Problems with thinking and visual perception may occur years before the memory loss of Alzheimer's disease becomes apparent, a new study finds. The findings may add new clues to identifying Alzheimer's at an earlier stage, when treatment may be most effective.
"Recent studies have focused on identifying the beginning of the transition from healthy aging to dementia," the authors write as background information in the article, which appeared in the Archives of Neurology, a medical journal from the American Medical Association. "As new interventions become available, it will become important to identify the disease as early as possible."
Current Alzheimer's medications may help ease symptoms for a time, but they do not stop the downward progression of memory loss and thinking problems. It is hoped that new drugs may be developed that will stem the losses of Alzheimer's, and that they could be given at the very earliest stages of the disease so that damage is limited.
Loss of memory and an inability to remember recent and past events are hallmarks of Alzheimer's disease. But problems with thinking and changes in personality also occur. This study examined a range of cognitive abilities to look for early clues to Alzheimer's onset.
Researchers at the University of Kansas in Lawrence assessed 444 individuals. None had serious memory problems or Alzheimer's at the start of the study, in 1979, when they underwent a thorough medical examination as well as tests of overall cognition, verbal memory, visual and spatial skills, and working memory. They were followed for up to 25 years (an average of 6 years), with additional tests.
On follow-up, 134 of the study participants developed dementia, and 310 did not. Forty-four of those with dementia underwent brain autopsies that confirmed a diagnosis of Alzheimer's disease.
Using data from the earlier memory and thinking tests, the researchers constructed models to see which memory or thinking problems might presage Alzheimer's. They found that problems with visuospatial skills were among the earliest signs of Alzheimer's, preceded a diagnosis by an average of three years.
"A novel finding was that visuospatial abilities demonstrated an inflection point [sudden change to a steeper slope of decline] three years before clinical diagnosis," the authors write.
Visuospatial skills encompass a range of abilities, many of which are essential for living independently. Completing a jigsaw puzzle, gluing the pieces of a broken vase together, reading a map or giving directions, or navigating from one room of the house to another all depend on visuospatial abilities. Intact visuospatial areas of the brain also allow you to judge the time needed to cross a street before the light turns red or traffic approaches.
Declines in overall cognitive abilities occurred on average two years before before diagnosis of Alzheimer's whereas inflection points for verbal memory (the ability to recall words) and working memory (remembering things in the short term) were not seen until one year before clinical diagnosis. Such declines were not seen in individuals who remained cognitively healthy.
The findings shed new light on symptoms that may be early harbinger's of Alzheimer's disease. If an older person is going about their life in a relatively steady course for many years but then begins to have problems navigating, it may be an early sign of Alzheimer's. Problems remembering people or words or recent events, may be the first signs of Alzheimer's, but many healthy individuals experience these problems also. Nevertheless, such problems in the elderly, if troublesome, should be evaluated by a physician.
David K. Johnson, Ph.D.; Martha Storandt, Ph.D.; John C. Morris, M.D.; James E. Galvin, M.D., "Longitudinal Study of the Transition From Healthy Aging to Alzheimer Disease." Archives of Neurology, October 2009 (Volume 66, No. 10); pages 1254-1259.