AS of March 27, 2011, there were 36,000 more people in Scotland aged 65 and over than there were people aged under 15.

This is new, and therefore interesting.

It is especially interesting, I'd have thought, for the now-outnumbered young. Still more pairs of slightly failing eyes to keep you under surveillance. Still more unfeasibly old sorts to share their wisdom amid the ruins – nice job, that – of a crashed economy. Better get used to it.

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Self-evidently, we had all better get used to new demographic realities. We could start, perhaps, by minding our language. One TV report I saw on the first release of census population estimates moved smoothly from a mention of "65 and over" to a discussion of "the elderly". These are not, surely, still one and the same thing?

True, on modern measures of healthy life expectancy – as opposed to mere survival – 65 is still the mark of what it means to be old for too many Scots. Sadly, though, that fact has more to do with health inequalities in parts of Glasgow and their effect on averages than with common experience. Outside pockets of deprivation and hellishness, 65 no longer means elderly.

We are living longer: so much is obvious. Equally, the frailties and ailments associated traditionally with age are being postponed. Tens of thousands of those "65 and over" are in disgustingly rude health. Meanwhile, the Office for National Statistics (ONS), using figures for England Wales, reports that even existing life expectancy projections are misleading, and out by roughly six years.

In other words, instead of living to 79 – 76 if Scottish, on the last estimate – a boy born in 2010 can expect to live to the age of 85. Girls will push on to 89. Recent figures for the most common age of death in England and Wales tell their own story, apparently, and there is no obvious reason for them not to be replicated in Scotland.

More interestingly, the ONS can see no reason why the process should not continue indefinitely. The biblical three-score-and-ten is patently out of date. But so too, say the statisticians, is the old assumption that there must be a natural upper limit – 90 was once the best guess – to age. We will, it seems, go on and on. And where does that leave us?

The first fear, obviously enough, is economic. Even by this week's estimate, 854,000 (under 15) into 890,000 (65-plus) won't go. A lot of pensions are at stake. If we are not to disgrace ourselves, a great deal of health and social care will have to be paid for. The austerity propaganda of a Coalition Government busy ruining young lives meanwhile holds that it would be wrong to saddle those under-15s with our historic debts. Put aside excuses for wealth inequality and that fact remains.

So we work longer. Few like it, most accept it. Not many years ago we were awash in articles – I wrote a couple myself – on the impending "problem of leisure" and the coming age of mass early retirement when we would each have decades to kill. The notion seems almost funny now.

If increasing longevity is to be managed, unemployment is, as that favourite Coalition word runs, unsustainable. Yet what do we see? Too many people are out of work while too many of those in work are crying out for more hours. As dismal GDP figures continue to prove, a lot of employment is simply unproductive. The low-paid zero-hours non-job will not see us through the new era.

Worse than all of that is joblessness among the young. Little is promised to the 854,000 on their way to adulthood, and less is being done. The chances of them being able to provide for themselves, whether thanks to student debt, cuts, the housing market, or older workers refusing to budge, diminishes monthly. Yet we blithely presume that they will work until 70 to keep the entire system going.

In all of this, one big, disturbing question goes unasked. It is not posed by the ONS. Politicians, most of them, would not touch it with a barge-pole. The medical profession gets itself into all sorts of ethical tangles if the inquiry intrudes into arguments over geriatric care. How old is too old? If the statisticians are right, if there is no upper limit to life, the problems of longevity will accumulate. Must we accept them as inevitable?

Doctors work hard and long to extend life: they could hardly do otherwise. Each census demonstrates that they have been remarkably successful. Working people fret more over pensions than once they did precisely because medicine all but promises that 65 is no longer death's door. But perpetually increasing longevity, aside from being unprecedented in human history, threatens to redefine the meaning of life itself. And we refuse even to think about it.

Scotland's population estimates contain one interesting nugget, for all that. The number of those under five has gone up by 6%, from 277,000 to 293,000. Those who have a problem with immigration and immigrants might care to suck on that fact. If anything is likely to bring Scotland's population back into a manageable balance it is the phenomenon of the new Scot.

The alternatives are social as well as economic. Far be it from me, with one eye on the clock, to claim that older people tend to be a little conservative, or less likely to innovate, or reluctant to challenge long-held received opinions. Let's just say they become a little settled in their ways.

This isn't necessarily a bad thing, but inevitably it alters the nature of a society. It also leaves that society vulnerable to competition from countries with a more youthful, more eager and energetic, demographic mix. If Scotland has to adjust to increasing longevity, it had better also adjust its attitudes to the very notion of age.

Refusing to age physically, we must – for there is no choice in the matter – refuse to age mentally. Rowdy Septuagenarians for Scotland: not much of a slogan, but a start.