In Japan, during a recent business trip, I was invited by my host to taste something from a selection of the finest ‘sashimi’, which discerning HR gourmands will know is basically pieces of raw meat – usually fish – that have been intricately sliced and crafted into bite-sized morsels.

Now when I was growing up in Wigan, our idea of an exotic fish dish was when mum put our cod and chips on a proper plate and garnished it with a slice of lemon; so eating fish unbattered, let alone uncooked, is taking things very many steps too far for me.

I politely declined my host's offer.

One of the other guests, however, was keen to convert me to the wonders of this traditional Japanese delicacy. "Eating sashimi," he told me, "is one of the reasons that life expectancy in Japan is the highest in the world."

Now that statement resonated with an important HR issue I've been thinking about a great deal recently. Because, regardless of whether sashimi has a role to play or not, if Japan is the 'greyest' nation in the world, maybe Japanese people practices could provide us with some clues about the future shape of the UK workforce as our own population grows ever older.

So I started by checking the facts. And, indeed, Japan does have the highest proportion of older people in its population. It tops the US Census Bureau's list of the world's 'oldest countries', with almost a quarter of its population being over 65. The UK, on the other hand, scrapes in at 19th, with just one in six of our citizens having hit this milestone.

The most striking difference comes when you dig deeper. Although the official retirement age in Japan is 64 - and until 2002 it was just 60 - a much higher proportion of its people work past retirement age, with OECD figures for 2010 showing more than one in five over-65s are in employment. That is almost three times higher than the UK figure.

So, with the proportion of older workers in the UK expected to reach similar levels within the next decade or so to those currently found in Japan, how should HR here start preparing itself for a significantly older workforce?

This is a question the marketing profession is already beginning to address. This June, Andy Fennell, Diageo's chief marketing officer, warned marketers to stop being obsessed with targeting young people, as they risked neglecting a "valuable and influential" older audience.

I wondered if a similar accusation could be levelled at HR? Like the marketers, we would be crazy to turn our backs on the young - but it is also clear we can no longer afford to be blind to the skills and experience older workers can bring.

But will people want to continue working into older age? Well, market research in the UK has shown that three-quarters of today's fiftysomethings feel no more than 75% of their chronological age. So a 50-year-old feels a little over 35 and someone approaching 60 feels about 45.

If that trend is sustained, there are three key implications for HR.

First, wanting to work into our 70s will become increasingly common. Indeed, given the worsening pensions crisis, for many, working into later life may become an economic necessity.

Second, we may consequently have to reconsider the traditional 'linear' career path where an individual retires at the highest point of seniority and responsibility; and look towards a more 'parabolic' trajectory, which allows older employees to slowly reduce their workload - and their accountabilities - over a number of years.

And finally, the concept of the 'older worker campaign' will need to be pensioned off altogether because, quite simply, older workers won't feel… well, old. A sentiment of youthful joie de vivre, I hope, is shared by Chiyono Hasegawa, who celebrates her 115th birthday this month, making her Japan's oldest citizen and the world's second oldest.

Her secret for a long life? Well, believe it or not, it's hard work… and sashimi.

Smoked salmon sandwich, anyone?

David Fairhurst (pictured) is chief people officer, Europe at McDonald’s