Since Duke-NUS Graduate Medical School is modelled on the American system, it is not surprising that some students come from a non-traditional background, said Dr Craig Stenberg, associate dean of student affairs and admissions.

"Those interested in medical science have to do well in MCAT. Their skills are also enhanced by the additional knowledge of social sciences," he said.

Students are admitted only after the admissions committee is convinced they have the background and ability to handle a rigorous curriculum, he added.

They take about four years to complete the Doctor of Medicine (MD) degree.

Those opting for a more research-intensive career take about seven years to complete the MD/PhD programme.

Dr Peter Loke, adjunct senior lecturer at the National University of Singapore's Centre for Biomedical Ethics, said mature students are generally steadier and take challenges in their stride better.

"From my personal perspective, it also illustrates the person as a determined character (who) takes up such a challenge," he maintained.

As Singapore's population ages, the country has to grow its pool of doctors to meet rising health-care demands.

Last year, 279 new doctors graduated from Duke-NUS and the undergraduate NUS Yong Loo Lin School of Medicine, Health Minister Gan Kim Yong said.

The third medical school, Nanyang Technological University's Lee Kong Chian School of Medicine, takes in its first batch of undergraduates next year.

For mid-career entrants like Miss Tan, the biggest culture shock came from "being in an environment where everyone's talking in terms of what's good for the patient".

Previously attuned to a culture driven by dollars and cents, she found the new environment's empathy and concern for others refreshing, she added.

Any generation gap communicating with classmates, many of whom are about 10 years younger?

Amid laughter and good-natured protests, she said: "Their energy and enthusiasm are infectious.

And some of my younger colleagues are very idealistic, which I find heartwarming."

This article was first published in The New Paper.