It was during an evening stroll in January last year when his heart rate suddenly shot up and he struggled to breathe.

John (not his real name), a white-collar professional in his 40s who wanted to keep his personal details private, was rushed to hospital for emergency heart surgery. There, doctors discovered he had blocked arteries and deformed heart valves.

"Doctors were shocked... They didn't know whether I was born with it (the condition) or it was caused by a bacterial infection," said John.

Cardiovascular disease, which encompasses a range of problems from heart failure to congested blood vessels and stroke, has recently been found to kill more men than women for a variety of reasons.

And the Cardiac Rehab Programme at the National Heart Centre Singapore (NHCS), of which John is one of the 160 participants, has three times as many male as female participants.

The programme offers exercise therapy monitored closely by cardiac specialists, as well as health education and behavioural counselling.

A 2015 United States study published in the journal Proceedings Of The National Academy Of Sciences found that cardiovascular disease was mainly responsible for men having a shorter life expectancy than women.

According to government figures, life expectancy here last year was 80.6 years for men and 85.1 for women, and 3,395 men died of cardiovascular disease, compared with 2,498 women.

There are 963 men for every 1,000 women in the general population, according to Department of Statistics numbers.

Dr Calvin Chin, a consultant at NHCS, said that not only do more men develop cardiovascular diseases than women, but women here also develop the diseases about 10 years later than men.

The reasons for the difference are complex, he said.

The female hormone oestrogen facilitates the removal of bad cholesterol and therefore offers some protection against heart disease. In contrast, the male hormone testosterone, which stimulates high-risk behaviour and aggressiveness, has been linked to increased risk of heart disease.

There are also differences in lifestyle. "Male smokers tend to smoke a lot more (than female smokers), and men tend to deal with stress less well than women, being more prone to internalising stress instead of letting go," said Dr Chin.

"And because of their more forceful personality and egos, men are more hesitant than women to seek medical help when there's a problem."

A side effect of this well-known disparity is that women may be undertreated for heart problems.

Associate Professor Roger Foo, a senior consultant at the National University Heart Centre, Singapore, said his institution works to ensure that women are not neglected.

For John, the close call changed his life.

"It takes time to recover, and a lot depends on one's body and mindset," he said.

"It's not like a car, where we can just change the filter or the wheels when it breaks down."