Heart patients with obstructive sleep apnoea (OSA) are 50 per cent more likely to die from heart disease, or suffer from stroke and heart attack, within three years of undergoing surgery to treat heart artery blockage, a study here has found.

Of the more than 1,300 heart patients with successful stent implantations in the study, 2.7 per cent of those with OSA died from heart disease, compared with 1.1 per cent of those who did not have OSA.

The study, a collaboration between researchers from the National University Heart Centre Singapore (NUHCS) and China, India, Myanmar and Brazil, also found that 45 per cent of the participants suffered from OSA.

Obstructive sleep apnoea occurs when the upper airway closes partially or fully, causing breathing to be disrupted during sleep.

Symptoms include snoring and not feeling refreshed after sleeping the required eight hours.

Globally, people who have OSA are more likely to be male, elderly and obese, making them more prone to diabetes and hypertension due to their unhealthy body mass index (BMI).

However, researchers say that OSA is under-diagnosed and not part of the standard check-up for most cardiologists.

"Snoring is very common but there are medical implications - you don't really get enough oxygen. This causes the patient to be in a so-called 'stress state' and increases his or her blood pressure," said Associate Professor Ronald Lee, senior consultant at the department of cardiology at NUHCS.

For cardiologists inserting stents to treat coronary artery disease, it is important to screen the patients for OSA, he added.

The screening can be done through an overnight sleep study in the patient's home.

People with obstructive sleep apnoea who experience excessive daytime sleepiness can wear a mask which facilitates their breathing when they sleep, called continuous positive airway pressure. It is recommended that they wear the mask for at least four hours of their sleep.

They are also advised to lose weight. For Asians, they should aim to have a healthy BMI of between 18.5 and 22.9.

The NUHCS study was conducted from 2011 to 2015.

In a separate study conducted by Prof Lee and other researchers here in 2014, it was found that one-third of Singaporeans suffer from OSA, with Chinese and Malays more prone to it than Indians.