Figure 5

Histopathological differences in microglial aging between laboratory rodents and humans provide a foundation for normal and pathological aging. Mice and rats experience only normal aging due to their short life spans and controlled environment, whereas humans who live much longer lives are exposed to diverse environmental influences and lifestyles, including diets, physical and mental activities, drugs, pollutants, comorbidities and infections, all of which may affect the rates at which microglial senescence (dystrophy) occurs, indicated by different trajectories of dashed red lines. As dystrophy occurs to varying degrees there is a decline in microglial neuroprotection and with that neurofibrillary degeneration (NFD) increases at variable rates in different individuals.