I once made the mistake of using the word "elderly" in a news story to describe someone aged in their sixties. It's a mistake a journalist is only likely to make once, if the reaction to my use of the word is anything to go by: there was a deluge of mail slating me for the temerity of using "the E word" to describe someone of that age. I was in my early thirties when I wrote that ill-considered adjective - still in the throes of youth, when reaching one's seventh decade seemed simultaneously inconceivable and abhorrent. (Fifteen years later, I've adopted a rather more pragmatic view that growing old is much better than the alternative.)
I have no doubt these sprightly letter-writing sexagenarians would consider themselves to be, at worst, middle aged. But possibly not even then. Nobody, it seems, gets old any more. At the risk of incurring a new barrage of mail, it always seemed to me a matter of pure arithmetic: if youth, middle age and old age are of equal length, then you reach middle age one third of your way through your expected lifespan.
In the UAE, for example, the UN statistic for life expectancy is 78.7. The US expectation is a little lower, Australia and Britain a little higher. Based on that, middle age is from a little after your 26th birthday until about five months after you turn 52. In Swaziland, which has the grim notoriety of having the world's shortest life expectancy, 39.6 years according to the UN, middle age kicks in just after the 13th birthday. The CIA World Factbook calculates the nation's citizens' chances far more pessimistically, with 31.88 years as the allotted lifespan. That would make middle age kick in a little over six months after one's 10th birthday.
Have you ever heard of anyone in their late twenties describing themselves as middle aged? Me neither, although I haven't been to Swaziland. I've never even heard anyone in their thirties admit to it, when the only way you could statistically qualify to be still in the stage of youth is if you expect to live to 120. Of course, the truth is that youth, middle age and old age are not deemed to be equal parts. Much like vanity sizing in the fashion industry - and equally driven by denial - youth seems to have ballooned to include people who are 45 and possibly even older.
Maybe it's best defined relatively. As Oliver Wendell Holmes famously put it: "Old age is 15 years older than I am." So middle age could easily last up to the pension age. Even at that point, it seems that the E word could be used as an adjective. But anyone sensible will whisper it and not write it in a newspaper column.