RESISTANCE isn’t futile, especially when it comes to Alzheimer’s. Some people’s brains can withstand the ravages of the disease by elongating the connections between brain cells – a process that seems to counter mental decline.
Now we need to understand why some brains can respond to the disease in this way and to see if the effect can be enhanced with medicines or lifestyle changes.
Alzheimer’s disease, which causes memory loss and confusion, is the most common form of dementia. The condition is characterised by a build-up of a protein called beta-amyloid, which forms plaques between brain cells, and tangles of another protein called tau inside the cells.
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A long-standing mystery is why some people have plaques and tangles in their brain at autopsy, yet were mentally sharp when they were alive. This resistance to Alzheimer’s, seen in about a third of people who die without cognitive problems, is more common in those who stayed longer in education and had mentally demanding jobs. One idea is that intellectual stimulation builds a “cognitive reserve” – but it is unclear what physical form this takes.
To investigate further, at the University of Alabama at Birmingham and his colleagues studied brain samples from 41 people. They had either beta-amyloid plaques but no symptoms, plaques and symptoms, or no plaques or symptoms.
“It’s possible that the spines are reaching out to maintain the synaptic connections”
The team took close-up pictures of the samples, then used software to trace the physical shape of the brain cells and their connections, or synapses.
This technique allowed the team to visualise the first neuron of a pair that make up a synapse. This neuron sends out small buds known as spines, which connect with projections from other neurons – each synapse exists where a spine links to a projection. The spines of people who were Alzheimer’s-resistant were longer than those from the other groups (Annals of Neurology, ).
Synapses are where signals pass from one neuron to another. The longer spines might make the synapse more effective in this role, says Herskowitz. Or new spines might be growing outwards to generate more synapses to replace those destroyed by plaques and tangles. “It’s possible that the spines are reaching out to maintain the synaptic connections. They are putting themselves out there to catch a new one,” says Herskowitz.
While striking, the finding may not be the only explanation, says at the University of Sydney. Brain-imaging studies suggest that people who are resistant to Alzheimer’s may compensate for damage by using different parts of their brain.
Nor, by itself, does it tell us whether there is anything we can do to reduce our risk. “What this work does not address is whether the unique properties of those who evaded dementia are genetically endowed, determined early in life, or malleable throughout life,” says Valenzuela.
Animal research, on the other hand, hints that lifetime experiences can indeed ward off dementia. For instance, in mice genetically altered to develop a version of Alzheimer’s, mental , with play tubes and boxes.
For now, standard advice to reduce dementia risk is to do things like talking with friends, learning a second language – or even just doing crosswords, as well as staying in good physical shape.
Keep healthy with a mental workout
Could a brain-training game help prevent dementia?
Researchers at the University of South Florida gave 2800 people 10 training sessions across six weeks. Some people were taught memory tricks, others practised reasoning skills or received processing-speed training. A final group weren’t given any intervention.
Of the 1200 participants assessed up to a decade later, those who did the processing-speed training were less likely to have dementia than those in the control group. The other kinds of training made no difference to dementia risk.
The jury is still out, however, since the correlation was judged as statistically very weak.
This article appeared in print under the headline “You can defeat Alzheimer’s”
