Physical exercise can help counter the loss of memory caused by Alzheimer's as well as delay the onset of the most common type of dementia, according to a study.

Researchers at the Federal University of Rio de Janeiro (UFRJ), established a link between levels of irisin, a hormone produced by the body during exercise, and the development of the progressive disease, Xinhua news agency reported. The tests, carried out on rats with Alzheimer's, showed low levels of irisin in the brains of Alzheimer's sufferers, and a reversal in memory loss when irisin levels were boosted through physical exercise.

The study showed that "the levels of this hormone are in fact decreased in the brains of patients with Alzheimer's", said Sergio Ferreira, Professor at the UFRJ. In addition, the team showed that by boosting the levels of the hormone, "memory improves".

By showing that "irisin is an important mediator of the beneficial effects of exercise," the findings indicate the hormone can be "a novel agent capable of opposing synapse failure and memory impairment", said the study published in the journal Nature Medicine.

The research also reinforces the importance of physical activity in preventing memory loss and brain diseases, including Alzheimer's, the report said. Alzheimer's is a degenerative disease that erodes memory, eventually impairing language, reasoning and other mental functions.