She was still kicking her legs in a Highland Fling from her armchair when she passed 110. Jane "Jeannie" Gray - like so many of the world's super-centenarians - attributed her long life to good old-fashioned hard work and clean living. When she died,in Australia in 2014 at the age of 112, she was probably the oldest Scottish person ever.

After all, just a handful of Scots have ever passed 110, the super-centenarian milestone. The oldest to both be born and to die in the country were all 111.

Scots are not among the world's longest-livers. We do not even keep up with our neighbours in the British Isles or the rest of northern Europe. Nevertheless, in the course of just one - relatively short - lifetime something quite remarkable has happened: a twenty-fold rise in the number of Scottish centenarians.

READ MORE: New figures reveal over-50s are the fastest growing part of workforce

In centuries of record-keeping there was never as many as 50 people in Scotland aged more than 100. Then, in the 1970s, numbers started to rise. By 2004 there were 510. The last estimate, for 2014, put the figure at 910, most of them women. Expect further increases. In the early 1920s there was a mini baby boom in Scotland as life returned to normal after World War One. Some of those babies are about to come of age and get the now not quiet unusual telegram from the Queen, herself one of a growing cohort of British 90-somethings.

This is the sharp end of what politicians and policy-makers often describe as a 'problem': Scotland's ageing population. Over the next week The Herald will take a closer look at what ageing means for our society, and not just as a problem that needs solved. Our "Grey Matters" series will investigate many of the issues arising from the longer lives that so many of us are lucky enough to live. And they are far from all bad.

Take today: we are reporting on a monumental growth in the number of over-50s in the workforce. There are now 287,000 more grey workers contributing to our economy than there were at the turn of the century. Why? It is partly because a whole wave of working women getting older: more than half of the 50-plus workforce is female. And it is party because historic improvements in Scotland's once dire record on heart attacks and strokes mean more people. especially men, can keep working in to their 50s, 60s and 70s. This is no minor change in our labour market. These older workers, for example, outnumber all immigrants of any age from the EU by more than two to one.

The "active" old are not just in work: they are also doing the heavy lifting in the third sector, providing the lion's share of volunteers, including those helping with those older Scots who do need help.

Concerns about an ageing population are well rehearsed, but not, many demographers would suggest, well-heeded.

READ MORE: New figures reveal over-50s are the fastest growing part of workforce

For years experts have been warning of inescapable increases in the proportion of frail, elderly people putting huge strain on the public purse in general and social and health services in particular. Right now there are 75,000 people aged over 85 in Scotland. That number is predicted to reach 200,000 in 2037. With this comes a rise in the diseases of old age: there will be 20,000 living with dementia by the end of this decade. Cue more police wrapped up in missing persons cases involving elderly people with Alzheimers; more 999 calls for OAPs who have fallen in their homes; more social care; more home adaptations; and more and increasingly expensive geriatric medicine.

The growth of the 'very old' comes as the birth rate falls. Scottish women have not been producing an average of two children each, enough to maintain the population, since the early 1970s, back when somebody turning 100 was so rare it would make a news story. Thus the ageing population, even if not as acute in other countries or even the rest of the UK, is portrayed a demographic and fiscal impasse.

Other countries are further down this path. Life expectancy in Scotland is currently 77.1 for men and 81.1 for women. Those numbers are not particularly good, especially compared with those in our neighbourhood. Norwegian men can expect, on average, to see 80. So can Italians. English men are nearly there, with an average expectancy of 79.5. The differences between, say, England and Scotland pale in to insignificance when compared with the dramatic and well-documented chasm in health equality between the rich and poor in Scotland. Men in affluent East Renfrewshire have an average of seven more years on the planet than those in Glasgow.

There has been some evidence that the relentless rise in life expectancy in Scotland, albeit lagging behind our peer nations, has stalled. The effects of the financial crash and the subsequent policies of austerity may explain unusually high mortality in 2015 that in turn meant that average life expectancy over the last three years did not go up for the first time since the middle of the 19th century.

READ MORE: New figures reveal over-50s are the fastest growing part of workforce

Thus the pace of ageing is closely tied to major macroeconomic factors often beyond the control of any one generation of politicians or one party or movement. But, as recent events show, big demographic changes can be incredibly sensitive to constitutional politics. Scotland has mitigated against ageing in two ways in recent years that depend, to a large extent, on membership of the European Union. (So much so that some demographers joke that Scotland should pay extra pensions to older people who want to move to the Sun - stretching their lives and improving their health at low cost to the state). We have imported young workers to help pay for the old. And we have exported some of our pensioners to sunny countries, especially Spain. Will Scotland be able to keep attracting migrants after a Brexit vote that was mainly the result of anti-immigration sentiment in England? And will Spain be prepared to continue to provide services, especially health services, to non-EU Scottish migrants in the Canaries and Costa del Sol? With Scots again set to be asked if they want independence - once more throwing our demographic and pensions challenges in to stark relief - we should start to think smart about old age. Why? Because 'grey matters'.