I've always struggled learning foreign languages. 

At school, I just about scraped through my German GCSE, with my teacher kindly switching off the tape recorder to coach me on what to say between each exam question.

In my 20s, I picked up a reasonable amount of Afrikaans; enough to follow some conversations and share friendly greetings whilst in South Africa, but that's about it.

This new research from San Raffaele Hospital in Italy suggests that being bilingual can prevent cognitive decline and delay the onset of Alzheimer's disease. 

When I interviewed dementia expert Professor Jennifer Rusted as part of my documentary about retirement planning, she introduced me to this concept of cognitive reserve.

It's an interesting idea. By working your brain a bit harder - for example, by learning a second language - you create greater capacity within your brain so the same amount of damage results in fewer symptoms.

Professor Rusted described it to me as being like a window; you exercise your brain to create a bigger window, so the damage caused by dementia doesn't completely close this cognitive window.