DEMENTIA: AUSTRALIA'S FUTURE LEADING CAUSE OF DEATH?

Dementia deaths in Australia have steadily increased over recent years. In 2013, dementia became Australia's second leading cause of death, overtaking cerebrovascular diseases (strokes) for the first time. In 2014 and 2015 the number of dementia deaths have continued to rise. Ischaemic heart disease has been the leading cause of death in Australia since early in the 20th century, but while the rate of death from heart disease was at its worst around 1970, it has steadily declined since then. This article explores how and why our leading causes are changing, and questions whether dementia will soon become Australia's leading cause of death.


WHAT IS DEMENTIA AND HOW DOES IT LEAD TO DEATH?

Dementia (including Alzheimer's disease) is a collection of numerous symptoms caused by disorders affecting the brain, not one specific disease (Alzheimer's Australia, 2016). It can have severe effects on thinking, behaviour and quality of life. In 2012, Dementia was recognised as a National Health Priority Area in Australia due to its significant contribution to burden of illness and injury in the Australian community. According to the Australian Institute of Health and Welfare, approximately 342,800 Australians had dementia in 2015, with projections based on population ageing and growth estimating that this number will reach almost 400,000 by 2020 (see Australian Institute of Health and Welfare).

Deaths from dementia mostly occur because of complicating factors. These factors are often associated with issues such as immobility, incontinence, instability, malnutrition and impaired immune function. Sufferers can become frail, have breathing difficulties, and develop infections, all of which can lead to death. In cause of death terms, dementia is the condition that initiates these symptoms and therefore dementia is considered to be the underlying cause of death.


CHANGING DEATH RATES AMONG LEADING CAUSES

The graph below shows the standardised death rates for the past 10 years for Australia's top three leading causes of death. Over this period the death rate from dementia has increased from 28.6 to 40.1 deaths per 100,000 people. Death rates from both heart disease and strokes have decreased over the same time. The death rate from heart disease has decreased from 103.5 to 66.1, while the death rate from strokes decreased from 51.0 to 35.7.




AUSTRALIA'S AGEING POPULATION

The fact that Australia has an ageing population is well established. Over the 20 years from 1995 to 2014, life expectancy at birth for males increased from 75.0 to 80.3 years, while for females it increased from 80.8 to 84.4 years. As people live longer, the number of people surviving into older ages also increases. The graph below shows the changes in the age structure of the Australian population from 1994 to 2014, highlighting how the proportion of Australians in younger age groups has declined while the proportion in older age groups has increased.


Source: Population by age and sex, Australia, states and territories, Australian Demographic Statistics, Jun 2014 (cat. no. 3101.0)

Australia's top three causes of death are all diseases that most commonly affect the elderly. The median age of those who died from dementia in 2015 was 88.6 years of age (86.8 for males, 89.6 for females), while the median age at death from heart disease was 85.1 and stroke 86.6. Over the next 20 years, the number of Australians aged 80 and over is projected to more than double (see graph below). This will significantly expand the number of people most susceptible to heart disease, dementia and stroke, which in turn will put pressure on health services and will almost certainly increase the number of deaths from these conditions.




WILL DEMENTIA BECOME AUSTRALIA'S LEADING CAUSE OF DEATH?

Leading causes of death are determined simply by the number of deaths that occur from particular conditions each year. The below graph shows that in the 10 years from 2006 to 2015, the number of deaths due to dementia almost doubled, from 6,550 to 12,625. Over the same period, the number of deaths from heart disease decreased from 23,132 to 19,777 and deaths from strokes decreased from 11,479 to 10,869. Dementia is the only one of these three causes for which the death rate is increasing, in part due to the changing population structure, but also because medical treatments are not yet able to prevent or cure this disease. These factors mean it is highly likely dementia will soon overtake heart disease as Australia's leading cause of death. In fact, a simple mathematical projection based on counts over the past 10 years indicates dementia deaths will outnumber those from heart disease as soon as 2021. However, there are many factors which may yet influence patterns of mortality relating to our current leading causes, and only time will tell if current trends will continue or change. Regardless of the future ranking of Australia's leading causes of death, it is clear that as Australia's population ages, managing diseases of the elderly will be a critical issue as we seek to live longer, healthier lives. Footnote(s): (a) Dementia, including Alzheimer's disease (F01, F03, G30); Ischaemic heart disease (I20-I25); Cerebrovascular diseases (I60-I69) (b) All causes of death data from 2006 onward are subject to a revisions process - once data for a reference year are 'final', they are no longer revised. Affected data in this table are: 2006-2012 (final), 2013 (revised), 2014-2015 (preliminary). See Explanatory Notes 52-55 and A More Timely Annual Collection: Changes to ABS Processes (Technical Note) in this publication. See also Causes of Death Revisions, 2012 and 2013 (Technical Note) in Causes of Death, Australia, 2014 (cat. no. 3303.0). Source(s): Dementia, IHD, and CVD number of deaths, 2006-2015