People born in the years 1905 – 1930 who became very old showed little difference in neurodegenerative pathologies at autopsy. An exception was the density of deposits of the tau protein (neurofibrillary tangles), which was significantly greater in the later years of birth. However, the frequency with which Alzheimer’s dementia was pathologically diagnosed remained the same during the study period at about 65%.
Background
The proportion of elderly people in the population is increasing worldwide, and so is the incidence of dementias and other neurodegenerative diseases.So far, statistical recording has essentially been limited to the number of diagnoses. Possible changes in the underlying neuropathologies, on the other hand, have hardly been systematically researched
Design
Analysis of the autopsy data of 1554 deceased cohorts born between 1905 and 1929 (67% women, median age 90 years) from 2 US long-term cohorts («Religious Order Study» and «Rush Memory and Aging Project»). They were won over the years and thus extend over 25 years. In addition to the global appearance, the complete neuropathological examination included characteristic molecules such as tau and Lewy bodies, vascular changes and infarctions, and was statistically evaluated according to 4 birth epochs.
Results
- The prevalence of pathological diagnoses of Alzheimer’s dementia showed no differences between birth cohorts and ranged from 62 to 68%.
- The average severity of global Alzheimer’s pathology also showed no differences.However, the density of deposits of the molecule tau (neurofibrillary tangles) was greater in the later birth cohorts, namely age-standardized 1.53 for the years 1905 – 1914 compared to 1.87 for the years 1925 – 1930 (P = 0.01).
- In other neurodegenerative pathologies, no changes were found over time.
- Evidence of calcification of both larger and smaller vessels has been found «dramatically less frequently» over time. Thus, moderate to severe atherosclerosis was found in 54% of those born between 1905 and 1914, while only 22% were found in those born between 1925 and 1930.
Clinical significance
In the discussion, the researchers point out that above-average healthy people may have been recorded in their cohorts, which could limit the generalizability of the findings. They emphasize: Age-standardized, the increase in neurofibrillary tangles is not offset by more frequent clinical dementia diagnoses.This is an indication of at least partially improved resilience to pathology. They interpret the clear decline in pathological vascular changes as evidence of the improvement of several vascular risk factors at the population level, but without explicitly naming them.
Funding: National Institute on Aging.
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Source — https://www.univadis.de/viewarticle/keine-zunahme-pathologischer-alzheimer-diagnosen-trotz-2023a10005fc