Which are More Important In Alzheimer’s, Plaques or Tangles?

The brains of Alzheimer’s patients are characterized by the presence of microscopic changes that are descriptively called plaques and tangles. They were described by Dr Alois Alzheimer in 1906 when he first reported the disease bearing his name. Recent approaches in drug development have focused on preventing the development of one or other of these pathological changes. Attention has been chiefly on anti-plaque formation mechanisms, but a new finding reported at the Society for Neuroscience meeting suggests scientists may have been barking up the wrong tree.

Dr Chanzig Guela, of Northwestern University in Chicago, described the results of brain pathology exams in older people (80-year-olds) who had high-quality mental functioning. The subjects had to have a cognitive performance test result equivalent to that of a 50-year-old, be fully involved in personal and social activities, and have a major accomplishment, such as writing a book, after age 80.

On autopsy, the brains of 5 such high-functioning elders had only 25% the amount of tangles as the brains of 6 elderly people who had shown cognitive decline (but no dementia). On the other hand, beta-amyloid plaques seemed to be more extensive in the 5 high-functioning 80-year-olds than in the 6 controls.

Obviously, the numbers in this study are extremely small – the differences were not enough to reach statistical significance, and certainly not enough to draw definite conclusions. However, they suggest that there is a possible roll for accumulation of tangles in the causation of cognitive impairment and dementia. This may be sufficient for pharmacological researchers to switch their research direction to give tangles more attention than they have in the past . . .