More Evidence Dementia Is Caused By Multiple Conditions

A long term study has put forward intriguing evidence that dementia is the consequence of a number of ailments and risk factors, not a single cause

The new data comes from an analysis on more than 1100 people, combining two groups consisting of Japanese-American men and Roman Catholic nuns. With hundreds of available aging brains and autopsy data, the analysis hoped to unravel exactly what was happening in individuals diagnosed with dementia. 

"The impact on clinical dementia and impairment is largely unrelated to the type of lesion, or type of lesion combination. Rather, the driving factor seems to be just the total burden of disease"

Alzheimer's is the consequence, not the cause

The autopsies revealed that there were predictable patterns of 5 different brain lesions that began to take their toll as many subjects aged. These included: Alzheimer's disease, hippocampal sclerosis, microinfarcts, Lewy bodies and low brain weight. Lesions are essentially brain abnormalities. While signs of Alzheimer's were discovered in around half of all cases, the majority of these also displayed signs of another issue too. Curiously, many people with no sign of Alzheimer's exhibited considerable cognitive decline - indicating that decline is driven by a complex variety of problems. When many people are first diagnosed with 'Alzheimer's', doctors often find additional lesions too. 

Credit: Matthew Purdy

"I believe it's because all of these lesion types seem to be broadly distributed around the brain, each involving different neuron types and fields. So the result of their summation reflects the wiping out of multiple different systems within the brain, each required for optimal cognition"

The plot thickens

What does this mean? It means that as we age, a number of processes can fail or begin to occur in the brain, linked to a number of risk factors and processes. Possessing more of these appeared to drive cognitive decline more than any one did alone. A combination of these lesions takes a toll on brain function, and this manifests as dementia symptoms. Although right now it's not clear whether some of these lesions can be prevented, high blood pressure was established as one risk factor in this particular study for more than one pathology.  The whole picture really reinforces the fact we have to start tackling the aging burden as a whole, rather than picking Alzheimer's and attempting to 'fix' it without fixing any of the many underlying factors. 

"The good news is that preventing any of the pathologies will be of benefit to the process of aging-related cognitive decline. We can prevent illnesses currently diagnosed as Alzheimer's disease by preventing any of the other four lesion types, even if we cannot directly prevent the Alzheimer's lesions"

Read more at ScienceDaily