Rates unchanged in poorer countries of Africa, Asia, and South America.


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The number of people affected with dementia has fallen in each of the last two decades in North America and Europe. If this trend continues, 15 million fewer people in high-income countries will develop dementia by 2040, experts predict.

Figure. A new blood ... - Click to enlarge in new windowFigure. A new blood test for Alzheimer's disease measures tau protein, which forms tangles (the green areas on this slide of a brain cell) in the brains of Alzheimer's patients. Image by Thomas Deerinck / NCMIR / Science Source.

Researchers examined data from seven studies in six countries that involved nearly 50,000 men and women 65 years of age or older. They were followed for up to 27 years. The researchers determined that since 1998, the incidence of dementia fell by 13% per decade in high-income countries. The cumulative five-year decrease in dementia was greater in men than women, with a decline of 24% in men compared with only 8% in women. Lifestyle and other health interventions could further lower the number of dementia cases.


The decline in dementia incidence was not seen in Africa, Asia, or South America. Among potential influences on dementia rates are lifestyle choices such as smoking; variations in blood pressure, cholesterol, and diabetes management; and racial and ethnic factors. The researchers noted as a limitation of the study that it was based primarily on people of European ancestry living in Europe or the United States.


In other dementia news, a phospho-tau217 blood test is in development that can differentiate patients with Alzheimer's disease from those with other neurodegenerative diseases. Phospho-tau217 is a main component of brain tangles in Alzheimer's disease patients.


The test was given to 1,402 patients in three cohorts, two made up of people over 70 years of age with various neurodegenerative diseases, and the third consisting of younger people from families carrying the gene mutation associated with early-onset Alzheimer's disease. In the first two cohorts, the test correctly identified patients with an intermediate likelihood of Alzheimer's disease with 89% accuracy and those with a high likelihood of Alzheimer's disease with 98% accuracy. In the younger cohort, which included mutation carriers and noncarriers, the test was able to detect elevated levels of plasma phospho-tau217 as early as 25 years of age-20 years before the expected onset of mild cognitive impairment.-Carol Potera


Wolters FJ, et al Neurology 2020;95(5):e519-e531; Palmqvist S, et al. JAMA 2020;324(8):772-81.