ISCHAEMIC HEART DISEASE

Ischemic heart disease is the leading cause of death in Australia for both males and females. It is also the leading cause of death on a global scale. In 2015, heart disease caused 12.4% (19,777) of the 159,052 deaths in Australia, and 8.76 million deaths (15.5%) worldwide (Endnote 8).

What is ischaemic heart disease (I20-I25)?

Ischaemic heart disease, also called coronary artery disease, is a common term for the build-up of plaque (fatty material) in the heart’s arteries, causing them to narrow. This build-up is known as atherosclerosis, and results in reduced flow of blood and oxygen to the heart (ischaemia), which can lead to many serious acute and chronic health problems (Endnote 5). Acute manifestations of atherosclerosis include angina (discomfort and chest pains) and heart attack. Heart attack (or acute myocardial infarction), is a life-threatening event that occurs when there is a complete blockage of the blood vessel, starving the heart of oxygen and causing cell death and permanent damage. It is possible for people who have chronic ischaemic heart disease not to be aware they suffer from this condition until they experience angina or a heart attack.

In 2015, the vast majority of heart disease deaths were due to chronic ischaemic heart disease (55.3%, or 10,933 deaths) or heart attack (42.7% or 8,443 deaths).

Age and sex differences in heart disease deaths

In Australia, men die from heart disease at a rate around twice that of women, with this sex bias being consistent over time. The mortality rate for heart disease peaked in 1968. Since then, the decline in death rates has been dramatic for both sexes (see Graph 1, below). For males, the rate has dropped from 589.3 deaths per 100,000 persons in 1968, to 88.0 deaths per 100,000 persons today. For females, the decrease has been similar – from 304.3 to 47.4 deaths per 100,000 persons, when comparing 1968 to 2015.



Ischaemic heart disease deaths have a markedly different age profile for males and females. Graph 2 (see below) shows heart disease deaths as a proportion of all deaths, by age and sex. For women, the proportion of deaths due to heart disease increases steadily with age, peaking at 14.8% of all deaths among those 85 years of age and over. For males however, the proportion is higher from a much younger age. Heart disease causes more than one in ten deaths in males 45 years of age and over, accounting for similar proportions of deaths across age groups within that cohort.




Risk factors and presentation with other chronic illnesses

There are a number of risk factors for developing ischaemic heart disease. Some of these are not preventable, and include older age and a family history of the disease. However, most risk factors are modifiable, such as smoking, high blood pressure and cholesterol, diabetes, physical inactivity, being overweight, excessive alcohol consumption and poor diet (particularly through its negative impact on weight, cholesterol and blood pressure) (Endnotes 3, 6 and 7). Modifying these controllable risk factors reaps benefits both in terms of reducing the likelihood of developing heart disease, and also in limiting the progression of the disease, once it is acquired (Endnote 4).

Although ischaemic heart disease can cause death from early adulthood onwards, the majority of deaths occur in the elderly. As such, the median age for heart disease deaths is 85.1 years. With increased age comes an increased risk of developing multiple chronic health conditions, and in 90% of ischaemic heart disease deaths, it is reported along with other conditions on a Medical Certificate of Cause of Death. Hypertensive diseases and diabetes are known risk factors for heart disease, and commonly co-occur with these deaths.

In addition to the 19,777 deaths where heart disease is the underlying cause, another 16,675 deaths have heart disease reported as a contributing factor to a death from another cause. Deaths due to cancers, diabetes and Chronic Obstructive Pulmonary Disease (COPD) most commonly have coronary heart disease listed as an associated cause on the death certificate. In 2015, over one in five (22.9%, 36,452 deaths) Australians died either from heart disease, or with heart disease identified as a contributing factor to the death.

Ischaemic heart disease in Aboriginal and Torres Strait Islander Australians

Ischaemic heart disease is the leading cause of death among Aboriginal and Torres Strait Islander people¹. Aboriginal and Torres Strait Islander people suffer from a number of heart disease risk factors at higher rates than non-Indigenous people. The Australian Aboriginal and Torres Strait Islander Health Survey (Endnote 1) reports that rates of diabetes/high sugar levels, tobacco smoking, obesity and high blood pressure are all higher among Indigenous Australians compared to those who are non-Indigenous. From 2011-2015, the Aboriginal and Torres Strait Islander death rate from heart disease was 1.8 times higher than for non-Indigenous people (138.1 compared with 78.7 deaths per 100,000 persons, respectively).
Heart disease deaths account for a greater proportion of deaths of younger Aboriginal and Torres Strait Islander people than non-Indigenous Australians. From 2011-2015, more than one in ten (12.0%) deaths among 30-39 year old Aboriginal and Torres Strait Islander people were from heart disease, compared to 3.8% for the same age group in the non-Indigenous population.

Changes over time

The death rate for heart disease has been in steady decline over several decades. In 1968, the rate of death was more than six times greater than what it is today (428.3 deaths per 100,000 persons in 1968 compared to 66.1 in 2015). This decrease has been attributed to a number of factors, including improved diagnosis, improved treatment (including an increase in the use of medication to treat high cholesterol and blood pressure) and behavioural changes that have placed people at lower risk of developing or dying from the disease (for example, a reduction in smoking rates over time) (Endnote 4). For those with established ischaemic heart disease, advances in treatment have meant a reduction in coronary events such as heart attacks, and better survival rates after these events occur (Endnote 4).

Although great declines in heart disease deaths have been achieved over time, new challenges may be faced with an aging population and an increase in the prevalence of some risk factors for heart disease in Australian society. For example, the National Health Survey (Endnote 2) has reported increases in diabetes and a greater proportion of people who are overweight or obese. This may influence whether mortality rates from heart disease can continue to decrease in coming years.


Footnotes:
1. Data on Indigenous status are reported by jurisdiction of usual residence for New South Wales, Queensland, South Australia, Western Australia and the Northern Territory only. Data for Victoria, Tasmania and the Australian Capital Territory have been excluded in line with national reporting guidelines.

Bibliography

1. ABS (Australian Bureau of Statistics) 2013, Australian Aboriginal and Torres Strait Islander Health Survey: First Results, Australia, 2012-13, cat. no. 4727.0.55.001, ABS, Canberra.

2. ABS (Australian Bureau of Statistics) 2015, National Health Survey: First Results, 2014-15, cat. no. 4364.0.55.001, ABS, Canberra.

3. AIHW 2009. Prevention of cardiovascular disease, diabetes and chronic kidney disease: targeting risk factors. Cat. no. PHE 118. Canberra: AIHW.

4. AIHW 2014, Trends in coronary heart disease mortality: age groups and populations. Cardiovascular disease series no. 38. Cat. no. CVD 67. Canberra: AIHW.

5. Heart Foundation 2016, Coronary Heart Disease, viewed 15th June 2017 <https://www.heartfoundation.org.au/your-heart/heart-conditions/coronary-heart-disease-CHD>

6. Heart Foundation, Heart attack risk factors, viewed 15th June 2017 <https://www.heartfoundation.org.au/your-heart/know-your-risks/heart-attack-risk-factors>

7. Heart Research Institute, General Heart Disease: Know the facts, viewed on 15th June 2017 <http://go.hri.org.au/wp-content/uploads/2016/07/hri_general_heart_disease_ebrochure.pdf>

8. World Health Organisation 2017, The Top 10 Causes of Death, viewed 15th June 2017 <http://www.who.int/mediacentre/factsheets/fs310/en/>