A hormone released during exercise may protect the brain against Alzheimer’s disease. It may also explain the known positive effects of exercise on mental performance.

Irisin is a hormone generated by muscle tissue that is carried around the body in the bloodstream. Fernana de Felice at the Federal University of Rio de Janerio and colleagues found that people with Alzheimer’s had lower levels of the hormone compared with healthy individuals.

In tests with mice, the team could induce learning and memory deficits by cutting out irisin and could reverse the effects by restoring the hormone. When irisin signalling was blocked in mice with a rodent version of Alzheimer’s, the brain benefits of physical exercise were lost.


“We know that physical activity is linked to better brain health as we age, and this research highlights a biological mechanism that may contribute to this beneficial effect,” says Rosa Sancho at the charity Alzheimer’s Research UK.

Some people who are unable to regularly exercise but have dementia or are at high risk of dementia could one day be given drugs to target irisin. “Drugs designed to target the hormone identified in this research could potentially bring some of the benefits of physical activity to people who may be less able to exercise.”

“Although this study was only in mice, it adds to mounting evidence of the relationship between lifestyle factors, like physical fitness, and dementia,” says James Pickett at the Alzheimer’s Society charity.

Journal reference: Nature Medicine, DOI: 10.1038/s41591-018-0275-4