BUNGEE-jumping in New Zealand, snow-boarding in the Andes, white-water rafting in Goa, mountain-climbing in Malaysia — you don’t have to be a youngster to enjoy a gap year break these days.

Changing career patterns and a growing acceptance of sabbaticals among employers are contributing to a boom in career break gap years that threatens to overtake the traditional student market.

Latest figures from gap year companies show that about half of the 200,000 Britons who take long overseas trips each year are on career breaks, with one in four people deciding to “do something constructive” such as wildlife conservation or teaching in a third world country.

The figures are provided by the Gap Year Show, which is being held for the first time, with more than 60 companies taking part, at the Wembley Exhibition Centre on Tuesday and Wednesday.

It estimates that the number of “gappers” has more than doubled in the past decade, with employers recognising that breaks can reinvigorate members of staff working in stressful environments.

The usual length of a trip is six months to a year, with many people letting their homes or selling cars to fund dream holidays. The average amount spent is £6,000 to £9,000. The fastest growing group of gap year travellers is aged 28-40, and there has also been a burst of interest among the empty-nester over-55s.

“Grown-up gappers are the big trend,” said Tom Griffiths, founder of www.gapyear.com. “Companies realise that if they want to hang on to their best members of staff, then they need to offer the chance of unpaid leave as often as every three to five years. You’ve also got people who are opting for ‘portfolio careers’ in which they change job every five years or so to move on. In between jobs, many are taking long-haul trips.”

Griffiths believes there is a strong envy factor among people in their early thirties who went straight from secondary school to university and on to jobs, unlike friends who took time to travel in the early 1990s. “People who’ve reached their thirties really feel that they should have seen a bit of the world. Jobs are so rarely for life these days that people reach their thirties and wonder ‘where am I going?’ More and more are taking long trips.”

Cheap air fares have combined with recent movements such as the Make Poverty History campaign to encourage people to become involved in projects in countries such as Bolivia, Ghana, India, Vietnam, Mongolia, Sri Lanka, China and the Australian Outback.

“Many of our clients take part in a voluntary project and then go on to see more of the country. We have had several bookings for African safaris following a four-week stint at an orphanage in South Africa,” said David Stitt, director of www.gapyearforgrownups.co.uk, launched in April.

Another website — www.thecareerbreaksite.com, pitched at “bored British professionals” — has since sprung up, while Lonely Planet has published The Career Break Book. Charlotte Hindle, co-ordinating author, said: “Many people decide not to give up on their travel dreams for a mortgage, kids and a dead-end job.”

Human resources departments are adapting — but will consider applications only on “an individual basis”, rather than guarantee the right to take breaks. Oliver Felstead, graduate recruitment manager at L’Oréal, the international beauty company, said: “When someone has something they really want to do, then we are supportive. But we wouldn’t say yes unless we felt there was a positive aspect to the trip.”

The policy at Deloitte, the business advisory firm, is “to accept applications individually for unpaid travel up to a period of two years”. Accenture, PricewaterhouseCoopers, BT and Sainsbury’s also offer career breaks and the Confederation of British Industry estimates that a quarter of UK firms now offer career breaks.

Times recommends

• New York's top 10 new hotels
• A Scottish monastery retreat
• Welcome back to Rwanda