Out of the blue, just when we need him most, Bill Clinton is in hospital having heart bypass surgery. A significant arterial blockage was discovered, possibly caused by too many cheeseburgers and fries in his earlier life. But why would the blockage start to play up now, when he has switched to the low-carb South Beach Diet, is jogging regularly, and has retired? That blockage must have been building up for some time. Could retirement have anything to do with it?

Not that Clinton has really retired. He has just written his memoirs and been on a grand book tour, but scribbling away at home, spending time with his family, must surely be less stressful than being the most powerful man in the world with women crawling beneath your desk, the extreme right out to get you and the Middle East about to blow.

Before you take your life in your hands and opt for retirement, it might be worth knowing that there are two types of stress: nice stress and nasty stress. Nice stress probably includes ruling the world, earning a fortune, having a tight schedule, knowing what you're doing for every minute of the day, having a purpose, and knowing where and what you are. This is the lovely, buzzy-type stress - the sort that produces a hormone called dehydroepiandro-sterone-S, or DHEA-S for short.

This leads to better brain and memory function, it strengthens the body's defences, boosts the immune system, improves the complexion and lengthens your life. You get it when taking exams and doing parachute jumps, giving wedding speeches, in fight-or-flight situations, running countries, being president, or earning enormous amounts of money. It's a form of mind over matter. You can even delay death if you think something thrilling is about to crop up.

Nasty stress is the sort that drudges on for ever with no end in sight: endless debt, bereavement, relationship breakdown or bullying can bring it on, and this stress will give you high blood pressure, despair, palpitations, headaches, bowel upsets, insomnia and an increase in minor infections. Making a fortune probably gets the DHEA-S flooding out. It's the people in low-grade, low-paid jobs and in endlessly powerless situations who are likely to suffer the more destructive type of stress.

Perhaps, in his own way, this is what Clinton has switched to. He has less power and more anxiety. The prospect of Bush in charge until heaven knows when can cause tremendous anxiety, and Clinton is in a better position than most to know just how terrifying that prospect might be. How stressed must that poor fellow be?

Have you ever worked like a lunatic for months on end without a day off, then taken a holiday and been poorly for the whole of your time off? It's called leisure sickness and has flu-like symptoms. Again, you have probably left a structured, activity-packed lifestyle for a relatively empty, flopping-on-the-beach-type life, with plenty of time to feel anxious. Peter Nathanson, a successful and tremendously busy location manager on grand films with gigantic budgets and mega-film stars, rises before dawn for months on end, works like a slave, barely sleeps, never takes a day off sick, but is always poorly the minute he goes on holiday.

"This year I was OK for a week of my holiday in America," says Nathanson. "I managed the social whirl because it was a bit like work, but on the plane home I caught something. Two days later I had a temperature of 100F which went on for the last three weeks of my holiday. Back at work, everyone looked sharp as a button and I felt pasty-faced and blurry and 20 years older."

Retirement can be like holidays on a grand scale. Aeons of time to think for the rest of your life. James Tiplady, a stunningly efficient and inspiring music teacher, used to work like a slave as the head of the music department in an inner city comprehensive. I was a newly qualified teacher and he was a living dynamo. And then he decided to make life easier for himself and work part-time in a junior school. He suddenly flipped while playing chess, threw the whole board and pieces into the air, and wandered around in his pyjamas. It was as if an elastic band had finally snapped after years of relentless stretching. And that was only a small step towards retirement.

My friend Mavis's Uncle George was defined completely by his job as an eminent lawyer. Shortly after he retired, on his 80th birthday, Alzheimer's kicked in. In a room crowded with 40 birthday guests, he kept asking, "When are the visitors arriving? I mean the real visitors." To Mavis, his sudden decline seemed like the felling of a beautiful tree. "It's the way you retire that does it," says Mavis. She herself was sacked ignominiously and unfairly and almost immediately caught pneumonia, ending up in hospital for weeks. And look at our own Lady Thatcher. The last time I saw her on telly, she looked an absolute fright. Since her retirement she seems to have crumpled and gone even battier. All those years of intensive working and bossing and barely any sleep. What was she going to do with all that energy once she had retired?

A drastic change is probably asking for trouble. "It's a great shock if you've been working and you go to nothing," says Joan Bakewell, still writing and broadcasting at the age of 71. "You go from a solid income to no credibility, no place to go to every day. All your responsibility is taken away, you lose a major role, you have no identity. As freelances, we avoid all this, but we need some sort of structure: charity work, book group, grandchildren."

It is perhaps not a good idea to go at retirement like a tank, roaring into fitness regimes, extreme sports, thrilling cruises and fierce diets. Bakewell would not advise fierce jogging, and remembers President Jimmy Carter, who jogged seriously, looked rather pasty and nearly fainted. "Discreet exercise on the quiet is quite a good idea," says Bakewell. "And anyway, a heart attack is not the worst deal. It's better than a slow and nasty exit." She rather fancies a heart attack in the middle of Verdi's Don Carlos. "Very sumptuous. Those gorgeous crescendos might send my heart over the edge."

I'd prefer to hang on a bit longer, and have managed to smooth the change from work to retirement by not really doing either properly. I did one year of solid five-day-a-week teaching, cut it down to four days a week, couldn't imagine how I had managed five, continued to decrease my days of work until they were two and a half day's teaching, plus one as a street trader, and now here I am, diddling along, not really retiring. If one can bear to live on gruel and dress in rags, I recommend this method. I am a cheat, of course. I have a secure home, no debts and few worries, and the gruel and rags are not compulsory. If they were, I too might well be having chest pains.

Hopefully Bill Clinton will recover and even get back on to the campaign trail again. So take it easy, Bill, but not too easy. We still need you.

Retire? Not even if you paid me

One observes two kinds of people moving into retirement. The first are those who regard the process as a liberation, enabling them to do all they have longed to do: climbing serious mountains, or watching every match that Yorkshire play through the cricket season; writing the book that has long lurked at the backs of their minds, or spending time with the grandchildren. Work is over and will not be resumed whatever the temptation.

Then there is a second class - of whom I am one - who are so addicted to work that they go on working on much the same lines as before. Peter Preston, editor of the Guardian for 19 years, still writes columns for the paper, to which he has added copious book reviews and a succession of novels. His friends predict he will begin to think of retirement when he is 91. At 69, I have bought my first backpack and am touring the country compiling a book called Great British Bus Journeys.

Or perhaps there is a third category: those who for years have been counting down to their day of retirement but who, when it comes, haven't the slightest idea what to do. They hang about the house, reading the newspapers, pottering in the garden, spending too long in the pub, and getting in the way of their friends and families. Such people are vulnerable. They are simply at a loose end, and loose ends can get tied up in undesirable ways.

There is a long tradition of people dying within a few weeks or months of retirement, as if their purpose had been cut away from them. On close inspection it sometimes transpires that the opposite has been true: that the purpose from work has somehow kept them going when the odds were stacked against them. I think in this context of another great Guardian editor, AP Wadsworth, who, in failing health for a year, wrote his last leader - rallying the Labour party after Hugh Gaitskell had wavered against Anthony Eden's Suez adventure - on September 20, accepted the title of editor emeritus in October, and died on November 4. There are times when one "stores up" an illness until some important event is over. Some people, in the same way, seem almost to store up their deaths.

Retirement is like the great other events of life, especially marriage. Perhaps you can choose your time to go, deciding whether to quit, as so many do nowadays (though often not voluntarily), on or around your 55th birthday while there's still time for a new life. If so, what are you quitting for ? It's dangerous to exchange one kind of tedium for another. Or if the date is fixed, are you ready to make the most of that treasure, discretionary time - and how do you make the transition? Some make a clean break, jetting off to Copacabana or Cotopaxi. When I retired (well, sort of) one Friday three years ago, we treated ourselves to a weekend in Abingdon, a move ingeniously designed by my wife to ensure that the office didn't ring me over the weekend.
DM