The word retirement may be one that Dr George Khoo Swee Tuan never learnt.
Four months shy of his 90th birthday, the general practitioner, 89, still works full-time, running the Rochor Medical Centre 51/2 days each week.
And he has no plans to call it a day.
"It would be very hard to while away the time. I see some of my colleagues who retired too early and they became depressed or they suffer from dementia," he said.
"Many of my patients don't believe me when I tell them my age. I tell them I won't stop (working) as long as they come and see me."
The Singapore Medical Council (SMC) did not confirm if he is Singapore's oldest practising doctor, but he would have few challengers.
Dr Khoo, the youngest of four children, was born in Melaka in 1928. His father was the head of the post office and his mother was a school principal.
His childhood ambition was to teach as teachers were well respected and earned "quite good" salaries, he said.
Then came the Japanese Occupation, which changed the course of his life in Malaysia.
He saw how many teachers lost their jobs as many schools stayed shut during the Occupation. Schools that remained used Japanese as the language of instruction, so teachers who did not speak the language found it hard to find employment.
But, "during the war, even if people did not have money to pay the doctors, they paid in kind".
"They gave doctors chicken, vegetables, eggs, et cetera. It is the most recession-proof job."
After the war ended, he won the prestigious Federal Scholarship in Malaysia to study medicine at the King Edward VII College of Medicine in Singapore.
Former Malaysian prime minister Mahathir Mohamad was his classmate and the late Dr Toh Chin Chye, Singapore's former deputy prime minister, taught him physiology.
He described Tun Dr Mahathir as a close friend and they still try to catch up when they can, often discussing politics and other issues of the day.
Dr Toh, who was also the MP for Rochor, later roped Dr Khoo into grassroots work there.
In 1963, Dr Khoo joined his wife's uncle Ang Swee Hian at his clinic, Ang Clinic, in Rochor Road.
In 1977, after Dr Ang retired, Dr Khoo set up his own clinic, Rochor Medical Centre, at Rochor Centre.
"I'm known as the Rochor doctor as I have been here since 1963. I have treated three and even four generations of the same family," he said. "Some of my patients have moved away (from Rochor) but still come and see me."
During the war, even if people did not have money to pay the doctors, they paid in kind. They gave doctors chicken, vegetables, eggs, et cetera. It is the most recession-proof job.
DR GEORGE KHOO SWEE TUAN, on what he learnt during the Japanese Occupation.
Retired clerk Cheng Siew Choo, 79, said Dr Khoo has been her family's GP since the 1960s. "He's a very caring doctor who is very concerned about his patients. I'm thankful he is still seeing patients."
In the 1960s, Rochor was a "real rough town", said Dr Khoo. It teemed with brothels, gangsters, opium addicts and all kinds of patients, "honourable and not honourable".
For example, there were opium dens near his clinic and he was sometimes called there to treat his patients.
"The opium dens were very dark and smelly and I had to shout their names to find them. Some of my patients spent all their money on opium and they were too ill to come to my clinic," he said.
Gangsters were also a constant menace. Once, a gangster came to extort a princely sum of $200 in "protection money" from him. He had a knife tucked in his trousers but Dr Khoo kept his cool and bargained the sum down to $8.
Another time, just for the fun of it, Dr Khoo bought a parrot from a shop selling exotic animals near his clinic. Named Pepito, it would mimic his wife calling him, to the amusement of all. But it flew away one day and never returned.
Dr Khoo was also a long-time grassroots leader in Rochor, thanks to Dr Toh.
He would treat free of charge some of the poor patients sent to him by various groups, including a nearby church and fellow grassroots leaders.
Dr Khoo said: "After some time, I realised I enjoy the profession, curing and helping people. And I realised I'm doing some good."
He ran his clinic in Rochor until last year, when the Rochor Centre was closed, ahead of its demolition. He moved his clinic to Veerasamy Road in Little India, which is a 15-minute walk away.
Dr Khoo is married to retired radiographer Glory. They have two children. His daughter, Daphne, is trained in medicine and is currently the executive director of the Agency for Care Effectiveness, the national health technology assessment agency. His son Ian trained as a dentist and is now a regional director at Boston Scientific, which manufactures medical devices.
Hale and hearty, the grandfather of two is careful about his diet. He avoids rich food, red meat and tries to walk at least 5,000 steps a day.
He enjoys playing the piano, keeping up with the news and regularly attends medical seminars as part of the continuing medical education (CME) requirement for doctors to increase their medical knowledge and skills and be up to date in their practice.
A spokesman for the SMC says there is no age limit for doctors to practise here.
However, all doctors need to satisfy the current CME requirements by accumulating a certain number of points to renew their practising certificate. Doctors get points for attending medical seminars and lectures, among other educational activities.
Said Dr Khoo: "I will continue to work as long as I'm fit and I feel wanted and useful. If one day I feel I'm mentally and physically slowing down, I will retire."