A funny thing happened the other day when I was playing football. I went into a challenge with a player and he came out with a chipped tooth. Apparently my elbow was raised. He kindly suggested it was 50-50. The thing is he works with me. You could say he was a younger, fitter, better version of myself – a new Porsche with multi-media trimmings, compared to my battered Cortina.

When we arrived back at the office, I got a lot of funny looks from colleagues. "You broke Patrick's tooth!" "What could have possessed you?" There was even a rumour that I'd broken his jaw. My colleagues made the connection between our line of work, his relative youth etc.

I have always prided myself on my lack of competitiveness; my easy-going insouciance. Now as I approach my 50th year I am beginning to realise what a sadly misguided git I have been. Even this pride at my lack of competitiveness has been competitive.

American psychologists at the University of Oregon have just revealed that between the ages of 45 and 54, men are at their most competitive. Participants in its research were asked to solve maths equations, either on their own or head-to-head with a rival. Nearly 70% of those aged between 45 and 54 wanted an opponent, whereas only half of those between 25 and 34 did. It all makes a horrible kind of sense. The older, balder, fatter, stupider and more irrelevant we become, the more we feel we have to prove ourselves. So, I run obsessively, stare at my belly, imagining it morphing into a six-pack. When I go out with younger colleagues, there's a bit of me that wants to be able to drink more and vomit less than they do. Even my daughters have told me that these days I have to have the last word in arguments. I find myself going through homework, and saying appalling things such as, "What do teachers know? Listen to me", when I don't have a clue.

Still, at least I'm not as bad as my boss, who does a marine-style lunchtime workout. When he sees me going for a run, he smirks, calls me a sissy and says he's doing real exercise. Pathetic. I'd never do that. Well, not since the time I tried it out, found I was weaker in every respect, and vowed never to be seen in shorts with him again.

The less we can achieve it, the more we want it

Bald, hunched, paunchy, a stranger to buff, grimly aware that my sexual peak was 31 years ago, outpaced by my six-year-old daughter when we run for the bus, I know that, at 49, I'm on the down slope of the sagathon that's going to end in death. So it is good to know that that shows there is one area in which I haven't yet peaked. Previous research has shown that, as cortisol and testosterone decline, so do cognitive performance levels. But here's the twist.Older men want it more even if they can achieve it less - this explains why Ivan Lendl returned to tennis, and why I got embroiled in an incident at the pool last week. I was in the slow lane when I overtook an irritatingly lithe twentysomething swimmer who'd been lapping me. Breathless and smug, I lounged poolside on the edge of the pool - only to realise she'd stopped mid-length to chat to her personal trainer before resuming her implacable progress, damn her.

This incident confirms a gender split: : according to the report, men compete without regard for the likelihood of winning, whereas women don't compete if they can't win. I recognise this: women are more rational than men, though, because I'm competitive, I can't accept that truth.

Is this because men are happy only when asserting their dominance? Perhaps. There is something chilling - isn't there? - in Bernie Ecclestone's eyes when he appears in the shadow of his latest love, as if he's saying: don't you wish your girlfriend was hot like mine? To which the competitive male reply is to change the rules: don't you wish you were two feet taller like me? Nobody said male competitiveness was a beautiful thing.

If we can't win, but we can tilt the playing field until we do. That way we can be winners even as we mutate into the seven loser dwarfs of our declining years – wheezy, paunchy, hunchy, baldy, grumpy, squinty, and surly.

Stuart Jeffries