March was, as you may have been reminded by those cheerful fliers in M&S, Prostate Cancer Awareness Month. As W.H. Auden wrote, “cancer's a funny thing” and none funnier than the prostate variety. It kills someone in this country every quarter of an hour. They are all men, and virtually all - how shall we put it? - old geezers. Prostateland is very much a country for old men.

At the end of his fine memoir, Miracles of Life, J.G. Ballard announced almost casually that he had terminal prostate cancer. So his death this week prompted much sadness, but little shock.

At the end of The Smoking Diaries, Simon Gray dropped a similar prostatic bombshell. Whether he died of it, or just with it, a few months ago was not revealed. No matter. Men of a certain age will have closed Gray's volume with a twinge in the groin - and not lust. Books such as Ballard's and Gray's remind us that the cultural demography of Britain is shifting. There are more men over 55 (those damn prostate years) than there are young women in Jade Goody's cervical cancer danger zone. A government survey informs us (what every post office queue confirms) that between 1971 and 2004 the fastest-growing sector of the British population was “the oldest old”. The fastest-shrinking sector was the youngest young.

This, the report concluded, will have “significant implications in terms of welfare”. And, one might add, art, literature, film, theatre and music. Whom shall we follow into this new country of the “oldest old”?

Bob Dylan (b 1941) - always glad to play Moses to us benighted Israelites - is one candidate. Dylan's last album of new material was called, teasingly, Modern Times. “Old Timer” would have been more appropriate. The croaking voice of the 65-year-old singer was the audio equivalent of Walt Kowalski's face in the recent Clint Eastwood (b 1930) film, Gran Torino. The tracks were apocalyptic (Thunder on the Mountain, The Levee's Gonna Break), the whole album done with that chewed-to-the-bone country chickaboom accompaniment. The older, the simpler.

Philip Roth (b 1933) is another candidate. The enfant terrible of American fiction shocked the reading world 40 years ago with Portnoy's Complaint. Its comedy took off from the previously unmentionable fact that young guys jack off an awful lot more often than they strike lucky. Still do, probably. Flash forward to Exit Ghost (2007), the last of Roth's Nathan Zuckerman novels. The hero-narrator has undergone a prostatectomy gone wrong. He's an over-the-hill eunuch in diapers.

Paradoxically (like T. S. Eliot's withered, sexless Tiresias in The Waste Land) this endows him with clearer understanding of the human condition. The arc of life is complete, one feels, in Roth's late-life fiction: although the laughs are now few and far between.

“You're not getting older,” the TV ad used to assure middle-aged women, “you're getting better.” Do artists get better with age? It depends. One would happily chop 30 useless years off Wordsworth's late, largely unproductive life, and give it to Keats. John Lennon wasn't going anywhere when he died. Nick Drake (younger even than Keats) was. A life swap would be very much in order.

Some artists, such as Beethoven, with his late quartets, need many years to arrive at where they have to get to. One would be happy had Miles Davis never gone beyond Kind of Blue, and spared us all that pointless late-life tootling.

Others shoot their bolt early. Poetry, as he jested, had given up Philip Larkin in his fifties. Another ten years beyond the 63 he was granted would have been wasted. Give them to Keats. Or Sylvia Plath.

The prime purpose of older actors is to portray age convincingly. Robert De Niro (b 1943 and what Americans, rather alarmingly, call a “celebrity prostate cancer survivor”) was infinitely more persuasive as the evil old Bill Sullivan in The Good Shepherd than as the young, but cosmetically antiqued-up, Noodles Aaronson in Once Upon a Time in America. At sixtysomething (and post-prostate), De Niro could play it for real. I don't know if Gran Torino is a better movie than A Fistful of Dollars. What one can say is that Eastwood, its director-star, was not afraid to look what he is, a not terribly well preserved 78. It is also, correct me if I'm wrong, the first Eastwood film in which the star dies.

This, “the distinguished thing”, as Henry James called it, is where the artist of mature years comes into his own. When, in The Tempest, Prospero breaks his staff and goes off to live in a monastic cave, his every third thought, he says, will be of death. As the 90-year-old Diana Athill puts it in her memoir, Somewhere Towards the End, it only really makes sense when you are somewhere towards the end.

Dylan has another new album out this week, Together Through Life. Only a fool will ask: “Is it as good as The Times They Are a-Changin'?” The right question is: “Has he got there?” Is the arc complete? The lyrics of the lead track, Life is Hard, tease us with the hint that the man himself feels his end is nigh: “The sun is sinking low/I guess it's time to go/I feel a chilly breeze/In place of memories.” What do you make of that, Ricks?

W.B. Yeats wrote the line “That is no country for old men” in Sailing to Byzantium. It was popularised by the movie that scooped the 2008 Oscars. It is never easy to know what exactly those Coen Brothers are getting at. Nor precisely what Cormac McCarthy (b. 1933) meant in his 2005 novel. But it's clear what the 63-year-old Yeats meant. The old must leave sex to the young, who do it best, and embrace art. It's all they have, the only way that they can fight the years. Otherwise, “An aged man is but a paltry thing/A tattered coat upon a stick”.

There is a lot of debate about whether working people should retire at 65. God help us if writers, singers, film-makers, actors, musicians and artists do. Our old (and getting older all the time) country is going to need the wisdom and insight that only the old have about their “country”.

John Sutherland is Emeritus Lord Northcliffe Professor of English Literature at University College London

Times Recommends

• The ghost of Robin Cook haunts Chilcot’s feast
• The truth shouldn’t need oaths
• Violence: let’s separate the men from the boys