The debate on whether humans are the only species capable of developing Alzheimer’s has been reopened after the latest find in the area: a group of researchers has discovered telltale signs of Alzheimer’s disease in the brains of 20 elderly chimpanzees, once dead.
Despite the observed brain abnormalities, it is still unclear whether chimpanzees actually succumb to the disease or are immune to symptoms.
However, the results of the study could help scientists better understand the disease and how to combat it , although more research would be necessary, with the disadvantage that these animals are in danger of extinction.
While it is true that the brain abnormalities associated with Alzheimer’s disease had previously been observed in other ape species , including rhesus monkeys, baboons, and gorillas, they did not fully resemble the neuronal characteristics found in the brain of the humans with this type of dementia.
In the new study, led by biological anthropologist Mary Ann Raghanti, the brains of 20 chimpanzees aged 37 to 62 years were analyzed, which is equivalent to an age of 120 years in humans ; of these, 13 chimpanzees were found to have amyloid plaques, and another 4 also had the neurofibrillary tangles typical of the later stages of Alzheimer’s disease in humans, as published in the journal Neurobiology of Aging .
It must be remembered that the diagnosis of Alzheimer’s disease has three requirements : dementia and two distortions in the brain, namely amyloid plaques , sticky accumulations of misfolded pieces of proteins known as amyloid beta peptides; and neurofibrillary tangles , which form when proteins called tau are grouped together in long filaments that twist around each other like ribbons.
The study has been carried out thanks to a newly founded center that collects the brains of chimpanzees that die in zoos or research centers , since American chimpanzees have been in danger of extinction since 2015, when all invasive research on them.
Despite the evidence, so far only humans are known to display the triple combination of characteristics of Alzheimer’s disease: plaques, tangles, and dementia. Neither cognitive nor behavioral changes were analyzed in the 20 chimpanzees, so, according to the director of the study, ” we cannot say that these chimpanzees had Alzheimer’s , although we can say with certainty that they are the only other species that has its pathological characteristics. “.
The next step for Raghanti and his colleagues will be to go back to the analyzed chimpanzee brains to calculate the death rate of neurons , but proving that chimpanzees develop dementia will require research on live animals.
Few studies have tested how cognition changes in aging chimps. However, studies investigating memory loss, disorientation, sleep disturbances, and socially inappropriate behavior in chimpanzees may be tantamount to the cognitive deficits that accompany Alzheimer’s disease in people.
