It takes four to five years, costs tens of thousands of pounds, involves writing up hundreds of pages of research, and you don't even get to give up the day job. Why do people take a doctorate of business administration?

There is no single answer to this question. Motives range from the desire to move from business into academia, to hopes of career advancement within the business world, to sheer love of learning.

Chris Easingwood, professor of marketing and director of the DBA at Manchester Business School, says that his school usually has a small but significant group of DBA students in their late forties, who have had successful business careers but for various reasons want to get out of senior management and teach in business schools – and want to do it properly. By doing a DBA, "they can publish and become respectable members of faculty," he says.

While a PhD remains a more widely recognised doctoral qualification for academics in the UK, DBAs are a common route to tenure in the United States – indeed students studying business at doctorate level at Harvard graduate with a DBA – so it is particularly popular with American business people with ambitions to move into academia.

But Ken Starkey, professor of management at Nottingham University, suggests that the DBA is gaining greater recognition outside the US because of the increasing value placed on doctoral-level qualifications of any kind, and because of the shortage of business faculty with doctorates.

Six years ago the Association to Advance Collegiate Schools of Business International, which accredits business schools, issued a warning that unless decisive action was taken to reverse decline in doctoral business education, the quality of business education and research generally was at risk.

At the time, the number of doctorates produced by accredited schools was at its lowest level since 1987 and local demand outstripped supply in nearly all countries. A combination of low PhD enrolments and faculty retirements alongside rising student enrolments in management education means that AACSB International continues to forecast a shortage in the US alone of around 2,500 PhDs by 2012.

The accrediting body is so worried by the steep decline in doctoral-level business education that last September it launched a number of two-year training programmes for experienced doctoral faculty from academic disciplines outside business for faculty positions in management education.

But while the DBA offers business schools an alternative source of faculty recruits, it does much more than simply train for an academic career. It involves in-depth research, usually incorporating a year of study skills and a final thesis, carried out alongside students' regular employment. It attracts both people who are eager to understand a particular issue in their working lives, and those who get a thrill out of studying for its own sake. Other students are consultants who want to become world experts in a particular subject and for whom four years spent studying that subject in depth provides a career boost.

An increasing desire for self-development and people's perception of being personally responsible for their own career development has boosted numbers of students in recent years, says Naomi Brookes, DBA programme director at Aston, which is relaunching its DBA programme next month to emphasise its value to organisations as well as individuals.

Commander Mike Young, head of leadership and management at the Royal Navy, is a good example of this. He enrolled on a DBA course at Henley Business School after being asked to improve the way the Navy recruited and developed leaders. His DBA research has formed the basis for all future Royal Navy leadership training and has also influenced the police. His findings have earned him not only a promotion but an MBE.

Yet Starkey says some academics and organisations remain suspicious of the DBA because of its greater emphasis on applying theory, and the fear that it might challenge the more traditional PhD qualification.

It's certainly true that students need to be careful about where they take their DBA, advises Brookes. She says that Aston worked hard to be one of only five programmes worldwide that is accredited by the Association of MBAs in order to distinguish itself in a crowded market, where quality can vary considerably.

Grenoble Ecole de Management, another business school to have been recently granted the AMBA seal of approval, sees the accreditation as "a response to market concerns over issues of quality in an increasing international market for DBA programmes, and clarity over the nature of various postgraduate degrees in general management".

Starkey says that it is an interesting time for business education. For all their MBAs and continuing professional development qualifications, business leaders have not exactly proved themselves to be on top of their game in recent months, which has raised questions about the effectiveness of traditional business school models. As a result, he suggests, the alternative offered by the DBA, with its emphasis on the practical application of management theory, "could be very well placed".

'I'm not an academic or a practitioner. I'm a practical academic'

It was the gap between medics' approach to life and death situations, and the behaviour of business managers that inspired Colin Gruar to take a DBA.

The British Heart Foundation, where he worked as director of marketing, handled £100m worth of medical research a year. He was struck by how little the business world seemed to value theoretical knowledge by comparison.

"You wouldn't trust a heart surgeon who didn't know the latest research and how to apply it," he says. "Yet we trust the management of organisations with the corporate asset based on experience rather than the support of theoretical knowledge."

He continued to work for the medical charity during the four years of his DBA at Cranfield School of Management, where he looked at how an organisation develops a brand that speaks to a large and complex community of stakeholders.

After graduating in 2007 he drew on what he had learned to set up his own management consultancy, Repubrand, designed to help managers "achieve greatness" through acquiring and applying knowledge from around the world.

"I'm not an academic, I'm not a practitioner. I'm an academic practitioner or a practical academic," he says.

With a degree in mechanical engineering from Liverpool University, and an MBA from Cranfield taken 20 years ago, he says he looked into doing a PhD but preferred the DBA for its practical application.