If we can pin down how much it needs to be played, it would help a lot. Ms Winstone is conducting the research single-handed as part of her PhD studies. Mental decline is inevitable, just like physical decline. However just as keeping physically active helps ward off the signs of physiologically ageing, it may be that keeping mentally active helps to maintain mental alertness. She said people who played those games often used their mental skills in many other situations too.
People go and have a bit of fun.
It's good for people. It stops them becoming a couch potato.