Devoted football fans experience such intense levels of physical stress while watching their team they could be putting themselves at risk of a heart attack, research suggests.

Axar.az reports citing foreign media.

The Oxford study tested saliva from Brazilian fans during their historic loss to Germany at the 2014 World Cup.

It found levels of the hormone cortisol rocketed during the 7-1 home defeat in the semi-final.

This can be dangerous, increasing blood pressure and strain on the heart.

The researchers found no difference in stress levels between men and women during the game, despite preconceptions men are more "bonded to their football teams".