Losing a loved one really can cause someone to die from a broken heart, scientists claim.

They say that intense grief weakens the body's immune system leaving it more vulnerable to infections.

Academics from the University of Birmingham have found that increased stress levels and depression brought on by bereavement interferes with a type of white blood cell called neutrophils.

These are key to fighting certain bacterial infections such as pneumonia.

The researchers say the effects worsen with age as adults lose the ability to produce another hormone that can counteract the damage.

They believe this could in part explain why couples who have been married for years die months, weeks or even days apart.

Professor Janet Lord, who led the research, said: 'There are a lot of anecdotes about couples who were married for 40 years when one of them passes away and then the other dies a few days later. It seems there is a biological basis for this.

'Rather than dying of a broken heart, however, they are dying of a broken immune system. They usually get infections.

'We think that what is going on is that even in previously healthy people are becoming very depressed and this has a powerful effect on the immune system.'

Professor Lord and her colleagues looked at the immune systems and hormone levels of 48 healthy adults aged 65 and over.

Half of the group had suffered a major bereavement in the past 12 months.

They found that the ability of neutrophils to fight bacteria was lower in people who had suffered a bereavement.

They also had raised levels of the stress hormone cortisol, which is known to suppress the activity of neutrophils making them less active.

In 1995 former Prime Minister James Callaghan died of pneumonia aged 92, just ten days after his wife of 67 years Audrey.

And in 2003 musician Johnny Cash died of complications related to diabetes aged 71.

His 73-year-old wife June had died just four months earlier.