Dr. Larry Speaks and colleaguers measured tau levels in human plasma and found "significant differences" between cognitively normal individuals and those with either mild cognitive impairment or Alzheimer's disease. Levels of tau were significantly lower in plasma measured in those with diagnosed Alzheimer's disease compared to those with no sign of cognitive decline.

"As cognitive performance declines so do the circulating levels of tau," Sparks noted. The data suggest that changes in the circulating tau levels may represent a viable biomarker for tracking the progression of Alzheimer's disease and the efficacy of medications in its treatment. The levels of tau in cognitively normal seniors was nearly three times greater than those with cognitive impairment.

"Overall, the data suggest that changes in plasma total tau levels may provide a new avenue of identifying the onset of mild cognitive impairment and the ensuing Alzheimer's disease. The era of utilizing a simple blood test to help diagnose Alzheimer's disease is on the immediate horizon," Sparks reported.

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