Prime Minister Dr Mahathir Mohamad, who celebrated his 93rd birthday today, is currently the oldest head of government in the world.

However, Mahathir said he would have died when he had his first heart attack at the age of 64 were it not for medical advancements.

"Before there were heart surgeons, I wouldn't last. I would have gone down with the first heart attack.

"Before, if you open up the chest, you'll die because the lungs will collapse," Mahathir said in an Astro Awani programme that also featured Dr Yahya Awang, who led the team of surgeons who performed the procedure in 1989.

The nonagenarian said it was thanks to advancements such as the heart-lung machine that he was able to survive.

Yahya joked that on the morning of the surgery that he was offered asylum in the US.

"I still remember, the American cardiologist shook my hand on the morning of the surgery and said 'Yahya, if you need medical asylum you can come to America'," he said with a laugh.

Mahathir had two more heart attacks in 2006, and a year later underwent a quadruple bypass surgery.

All his heart treatments and subsequent chest infections have been treated at the National Heart Institute.

On the programme, Mahathir and Yahya also attributed the former's longevity to a mix of genetics and discipline.

Yahya said Mahathir listens to his doctors, takes his medicine, and exercises regularly.

Mahathir also repeated his mother's advice not to eat too much.