The leading theory in Alzheimer’s disease is that memory loss is the result of neuron death and nerve ending damage, which lead to memory loss, are caused by the formation of toxic protein clumps in the brain, called tau tangles and beta-amyloid plaques. But a new, small study challenges this theory, showing that the loss of neurons in brains of people with dementia is actually very small. What’s more, levels of neuron loss in patients did not indicate how far along the were in the disease, suggesting neuron death has little to do with the symptoms of dementia.
The team was led by scientists from Douglas Mental Health University Institute, Canada and Université Pierre et Marie Curie, France. They studied 171 brains at different stages of Alzheimer’s disease. Their findings of little neuronal loss suggest that neuron death is something that occurs very late in Alzheimer’s, and it doesn’t have much of an effect on the progression of the symptoms of the disease.
“Much to our surprise, in studying the fate of eight neuronal and synaptic markers in our subjects’ prefrontal cortices, we only observed very minor neuronal and synaptic losses. Our study therefore suggests that, contrary to what was believed, neuronal and synaptic loss is relatively limited in Alzheimer’s disease. This is a radical change in thinking,” said Salah El Mestikawy, an associate professor at McGill University.
Researchers who worked on the study said this points to dementia being a disease of synaptic dysfunction, rather than the result of the death of synapses, or nerve endings. If scientists could pinpoint how and when this dysfunction happens, a treatment to halt it could stop the progression of the disease.
“Until now, therapeutic interventions have been aimed at slowing synaptic destruction. Based on our study, we are going to have to change our therapeutic approach,” says El Mestikawy.
It’s estimated that almost 50 million people around the world live with dementia, with around 10 million new cases each year.
This study was published in the journal Scientific Reports.