When does "middle age" begin?

BBC reports: "Middle age starts much later than previously thought - at the age of 55, research suggests."

But the "research" is just a survey of what people think. If "middle age" begins at 55, the term is pure fluff, like saying some geezer is "95 years young!"

Although seven out of 10 early 50-somethings quizzed for the survey defined themselves as middle-aged, the average age at which the period of life was perceived to start was 54 years and 347 days old.

However, a sizeable minority, nearly one in five, thought middle age did not begin until after the age of 60.

One of the stupidest arguments I've gotten into in my entire life was with a 60ish female family member who insisted that "middle age" began at 60 (or something like that). I was in my 20s at the time and tried to be reasonable and accurate about what "middle" means in relation to the average human life span. And when I say the argument was stupid, I mean that I was stupid not to see the nature of the argument and bow out quickly.