How exercise protects against Alzheimer's
Exercise could protect against Alzheimer's by triggering a hormone which helps regrow brain cells.
Scientists have known for some time exercise reduces the risk of developing dementia, but did not know if there was a direct link or whether ill people were simply unable to work out.
A new series of studies has shown a hormone released during exercise, irisin, is depleted in the brains of people with Alzheimer's, and can protect animals against memory loss and brain damage.
Mice who swam nearly every day for five weeks did not develop memory impairment despite getting infusions of beta amyloid - the brain-cell clogging protein implicated in Alzheimer's.
It suggests not only that exercise protects against dementia, but a drug which mimics irisin could prevent the disease.
"I would certainly encourage everyone to exercise, to promote brain function and overall health," said Dr Ottavio Arancio, professor of pathology and cell biology and of medicine at Columbia University.
"But that's not possible for many people, especially those with age-related conditions like heart disease, arthritis, or dementia.
"For those individuals, there's a particular need for drugs that can mimic the effects of irisin and protect synapses and prevent cognitive decline."
Recent research has shown that irisin promotes cell growth in the hippocampus, which is a region of the brain associated with memory and learning.
Only two areas of the brain are able to regrow brain cells in adulthood, and the hippocampus is one of the first to deteriorate when people are suffering from Alzheimer's disease.