Yesterday I struggled to complete a Times 2 crossword and this morning, I couldn't find my car keys. Plus I left my sunglasses in a café. The reason? Old age.

At 26 (27 next month) I hadn’t really considered myself over-the-hill. In fact, I had liked to think that I had not quite yet reached my prime – if I wasn’t already in it. But according to newly released research, published in the journal Neurobiology of Aging, our mental abilities begin to decline from around the age of 27.

The paper, When does age-related cognitive decline begin? says age-related cognitive decline begins in healthy educated adults when they are in their 20s and 30s. Researchers studied 2,000 men and women, aged 18-60, who had to solve visual puzzles, recall words and details, and spot letter and symbols. They found that the average top performing age was 22 and the first age which performance was considerably lower than the peak scores was 27.

But fear not fellow pensioners. Apparently there are special brain exercises we can do to boost our mental ability, involving a specific combination of mental arithmetic and word games. I just can’t for the life of me remember what they are.