I used to live my life in fear of cancer – now it's dementia that worries me most

In my forties and fifties, not a day passed without the fear of cancer present at the back of my mind. Friends died, others went through long and painful chemotherapy. My sister passed away after suffering from brain and lung cancer.

The disease operated like a lottery, not differentiating between those who led healthy lives and wore sun block, and those who smoked and drank too much. One friend died from skin cancer less than a month after diagnosis.

What can you do? Have regular check-ups and cross your fingers. I refuse to get dragged into negative thinking.

But now that deep-seated, ever-present fear of cancer has been replaced by another big black cloud, equally impossible to ignore: dementia.

Every day we hear how many people are going to suffer from the disease – up to one in three – and it is already the leading cause of death, according to research published this week. Over a certain age, you wake up and do memory tests to check your brain is still OK. You reconstruct what you did the previous day, trying to remember phone numbers and names, anything to offer reassurance that the dreaded D isn’t taking hold.

A cure for dementia remains a long way off, although scientists have made a breakthrough, editing the DNA of rats to partially restore their sight. Genome editing, fixing “broken genes in the brain”, may eventually offer a cure for dementia. But how do you live with the diagnosis? Researchers also claim that computer games can be used to spot dementia earlier, by testing our map reading skills. I’m not sure I want to play the game without a cure on the horizon.

Researchers at Kings College in London reckon there’s a “genetic signature” they can identify in people who are ageing well, which must surely include the ability to shun a sat nav. In the meantime I shall still wake up every day, do my memory tests, and try to ignore that big black cloud. Nothing ages us more than negative thinking.