But the Australian Bureau of Statistics report shows the number of people dying from the illness has fallen since 2003, while Australian deaths from dementia and Alzheimer's disease are on the rise.

In 2012, coronary heart disease caused more than 20,040 deaths in Australia, almost double the number of deaths from the next most common cause, cerebrovascular diseases, which included haemorrhages, strokes and blocked brain arteries.

Heart disease accounted for 14 per cent of all deaths in 2012 compared with 19 per cent in 2003.

Dementia and Alzheimer's disease were the sixth most common cause of death in Australia in 2003, but moved to third in 2012, rising from 4270 to 10,370 deaths a year.

Heart disease was also the most common cause of death in the ACT, where it was responsible for 221 of 1700 deaths in 2012.

Alzheimer's Australia national research manager Chris Hatherly said it was not surprising more people were dying of dementia as Australia's population aged, because older people were more likely to develop the condition.

Dr Hatherly said there were 332,000 people in Australia with dementia and, unless new ways to prevent or treat the condition were found, another 3 million would develop it by 2050.

"Given it's a terminal disease and people generally don't live more than five or 10 years with the condition, most of those 3 million people, all of whom are alive today, will … die with it," he said.

The bureau warned changes to the way conditions were classified could have contributed to the number of deaths from dementia.

The Heart Foundation's director of cardiovascular health Rob Grenfell welcomed the drop in heart disease deaths, which he attributed to improved medication and patient care, tobacco control and campaigns on recognising signs of heart attack.

But Dr Grenfell warned against complacency, because high rates of obesity put many at risk of heart attack. "Unless we have concerted efforts to find [obese people] and to decrease their risk, heart attack is not going to go away as the leading cause of death," he said.

High survival rates meant more people were living with heart damage and were disabled by it, he said.

The bureau's data revealed suicide was the leading cause of death for men and women aged 15 to 44 and accounted for more than 2530 deaths across all age groups.

Trachea, bronchus and lung cancer was the fourth most common killer in 2012 and chronic lower respiratory disease was the fifth.

Diabetes was the sixth most common cause of death in 2012; in 2003 it was ninth.

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