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MORTALITY TRENDS OF PEOPLE AGED 50 YEARS AND OVER
SELECTED CAUSES OF DEATH AND THEIR CONTRIBUTION TO GAINS IN LIFE EXPECTANCY AT AGE 50 YEARS
In 1970-72, six specific causes of death were responsible for 80% of all deaths of people aged 50 years and over. In 2002-04, these same selected causes of death were responsible for 75% of all deaths of people aged 50 years and over. However, the death rates in the latter period were generally much lower than in 1970-72 with the all-cause standardised death rate falling by around half for both males (down 51%) and females (down 48%).
As would be expected, the causes of death with the highest death rates have a greater potential to contribute to improved life expectancy through their reduction than the less significant causes.
Reductions in deaths from ischaemic heart disease and cerebrovascular disease (stroke) have been key to improvements in life expectancy at age 50 years in recent decades. Reductions in associated risk factors and improvements in treatment and care have been instrumental in reducing deaths from these causes. On the other hand, the small overall declines in cancer death rates for people aged 50 years and over have not translated into significant gains in life expectancy.
DEATH RATES AND AGE-STANDARDISING
Death rates in this article use averages of three years of deaths data for each period (i.e. 1970-72 and 2002-04) and the estimated resident population for the middle year of each period as the death rate denominator.
Death rates used for comparisons of particular causes of death over time have been age-standardised. Age-standardising adjusts death rates to remove the effect of differing age structures of populations when making comparisons of death rates. The standard population used was the 2001 estimated resident population.
Analysis in this article uses the concept of the underlying cause of death. Underlying causes of death are classified by the disease or injury which initiated the train of morbid events leading directly to death. Cause of death data are obtained from the ABS Causes of Deaths collection and are presented according to the International Classification of Diseases, 10th revision (ICD-10). ABS publish comparability factors to account for the introduction of the Automated Coding System in 1997 and these have been applied to the 1970-72 deaths. (End note 3)
Ischaemic heart disease
In 2002-04 ischaemic heart disease accounted for one-fifth (20%) of deaths of people aged 50 years and over. In 1970-72, over one-third (35%) of deaths were attributed to ischaemic heart disease. The male and female standardised death rates for ischaemic heart disease of those aged 50 years and over fell by around two-thirds (70% and 68% respectively) (graph 9.10). For males aged 50 years, the result of this decrease has been a gain of 4 years of life expectancy (just over half of the total gain in the period). Females gained 2.9 years (or 45% of the total female increase in life expectancy at age 50 years) from declines in ischaemic heart disease death rates (graph 9.11).
Cerebrovascular disease (stroke) was responsible for 10% of deaths of people aged 50 years and over in 2002-04 and 16% in 1970-72. Over the period, death rates also decreased dramatically with declines of 70% for males and 71% for females. These were estimated to have contributed 1.1 years to male and 1.8 years to female life expectancy at age 50 years in 2002-04.
Cancer was the cause of more deaths than any other selected cause for people aged 50 years and over in 2002-04 with 29% of all deaths. In 1970-72 the proportion was 17%.
Compared with the other major causes of death, cancer death rates have declined relatively slowly. In the 32 years to 2002-04, the standardised death rates for people aged 50 years and over declined by only 6% for males and 4% for females. This small reduction in death rates was reflected in a minor contribution to increased life expectancy at age 50 years - around five months for males and two months for females.
Males had an 18% decrease in the lung cancer death rate over the 1970-72 to 2002-04 period, contributing around three months to male life expectancy at 50 years of age. Females, on the other hand, had an increase of more than two and half times (163%) in their lung cancer death rate, equivalent to almost a three-month reduction in life expectancy for women aged 50 years. This reflects an increase in smoking rates among women in the latter third of the 20th century.
Female breast cancer and colorectal cancer death rates declined by 13% and 37% respectively. Together they added around three months to life expectancy. Males also had a (17%) decline in colorectal cancer death rates, although the impact on life expectancy was less than one month.
Diseases of the respiratory system
Deaths from diseases of the respiratory system (mainly pneumonia and other obstructive pulmonary disease) made up 9% of all deaths in 2002-04 and 7% in 1970-72.
For males aged 50 years and over, the standardised death rate for diseases of the respiratory system decreased by 46% and contributed around eight months to male life expectancy at age 50 years. Among females however, there has been no reduction in the death rate from this cause. As with lung cancer, this may also be attributed to the increase in womens' smoking prevalence in the latter part of the 20th century.
Endocrine, nutritional and metabolic diseases
Deaths from endocrine, nutritional and metabolic diseases (mostly diabetes mellitus) was the underlying cause of 4% of deaths for people aged 50 years and over in 2002-04 and 2% in 1970-72.
Between age 50 and 79 years, males experienced a decline in the death rates for endocrine, nutritional and metabolic diseases, but this was offset by an increase in the death rate from age 80 years. Females had a similar pattern except the increase in the age-specific death rate was seen at age 85 years and over only. The impact on life expectancy at age 50 years for males was negligible, and only around two months for females.
External cause of death (accidents, poisonings and violence) contributed 3% of all deaths of people aged 50 years and over in 2002-04, and 4% in 1970-72.
The standardised death rate for this cause has halved for both males and females. As a lower order cause of death, however, the effect on life expectancy at age 50 has been small - around four months for both males and females. Suicide deaths contributed one-quarter (26%) of male external causes of death, although the rate was 39% less in 2002-04 than in 1970-72.
ABS has produced population projections from 2005 to 2101 that are underpinned by assumptions of future mortality in addition to fertility and overseas migration. The medium series projection assumes life expectancy will continue to increase until 2051 where males aged 50 years could expect to live to 86.6 years, while females aged 50 years could expect to live to 89.1 years (see Population projections in the Population chapter). These projections represent increases of 6.0 years for males and 4.5 years for females over the 47 years from 2002-04 to 2051 (graph 9.12). They also point to a halving of the rate of increase in life expectancy experienced over the last three decades. While the average rate of increase in life expectancy at age 50 years for males was 3.1 months per year between 1972 and 2002, between 2004 and 2051 it is assumed to increase by an average of around 1.5 months per year. For females the rate of increase in life expectancy at age 50 years averaged 2.6 months per year between 1972 and 2002, while the assumption over the 2004 and 2051 period is for an increase of 1.1 months per year.
1. Australian Bureau of Statistics 1998, Deaths, Australia, 1997, (3302.0), ABS, Canberra.
2. Pollard, JH, 1989, 'Mortality changes and their economic consequences, with particular reference to cause of death', in Studies in Contemporary Economies, Wenig, A & Zimmerman, KF (eds), Demographic Change and Economic Development, Sprigen-Verlag, Berlin, Heidelberg.
3. Australian Bureau of Statistics 2006, Causes of Death, Australia, 2004, (3303.0), ABS, Canberra.