The Baby Boomers weren't the first teenagers but they were arguably the best. They took drugs, sex and rebellion to new levels and created a lucrative youth market in the process. My prediction for 2013 is that this generation of erstwhile rebels, now in their fifties and sixties, will transform the mainstream understanding of what it means to age.

The signs of change are already here. In the cultural sphere there are increasing numbers of unexpected successes about people over fifty. A film about older Brits in India - The Best Exotic Marigold Hotel - confounded expectations by becoming one of the UK's highest grossing films in 2012. While success of a book about a grandmother finding new love, Thursdays in the Park, was driven by Baby Boomer e-book purchases. We can expect many more like these in the year ahead.

And there are plenty of other indications that this generation doesn't conform to the usual expectations of 'older people'. They are more likely to set up successful new businesses and to be happier and better off than their younger counterparts. And, in a mirror of their younger reputation, the over fifties have the fastest growing rates of sexually transmitted diseases.

So it feels like the Baby Boom generation is on the cusp of a shake-up of ageing equivalent to the post-war explosion of youth culture. This generation is reaching the so-called retirement age but few of them call themselves 'old'. They are challenging our assumptions about being fifty to seventy and creating an equivalently lucrative market in the process.

But despite these shifts, it seems that we lack the right words to describe this age group. It is neither old nor young; it's somewhere inbetween. In fact, this age group has more in common with another transitional stage - the teenager.

So perhaps we need an equivalent term to 'teenager' to describe this stage between mid-life and old age. And along with a new language we should re-evaluate what it means to reach this point in our lives. This transition could be a real moment of opportunity - to reflect on what matters most to us, to give back to society, to plan ahead for our later years, and to make important changes to our lifestyles which will help us to age as healthily as possible.

Whatever we call them, the Baby Boomers are set to redefine ageing - hold on tight...this should be interesting.