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LONG-TERM MORTALITY TRENDS
Causes of death from 1908 to 1998
The overall death rate in Australia declined substantially throughout the 20th century. This period was characterised by a shift in disease patterns and the age at which people were dying. In the first half of the century, cause of death statistics were dominated by infectious diseases which tended to impact on the very young and the very old. This pattern changed during the second half of the century as degenerative diseases in the middle and older age groups replaced infectious diseases as the main causes of death (Omran 1971; Olshansky 1986).
During the period from 1908 to 1998 the standardised death rate for males declined from 1,982 to 760 deaths per 100,000 and for females from 1,618 to 460 (graph 9.5). The overall pattern of male and female deaths was similar during this period, although the ratio of male to female deaths converged marginally, from approximately 1.4 male deaths to every 1 female death in the 1900s to 1.1 male deaths to every 1 female death in the 1990s.
In the first half of the 20th century the greatest decline in death rates in Australia was in infants and in children aged less than five years (United Nations 1982). The death rate for boys aged 0-4 years declined from nearly 2,500 per 100,000 persons in 1908 to less than 600 in 1958, and subsequently to 137 deaths per 100,000 persons aged 0-4 years in 1998. The pattern for females was similar, with the death rate for girls aged 0-4 years declining from more than 2,000 to less than 470 per 100,000 in the first half of the century, to 111 per 100,000 in 1998. In 1908 children aged 0-4 years comprised 24.5% of all deaths, but by 1998 this percentage had declined to 1.3.
In the older age groups the greatest gains came in the second half of the 20th century. For example, during this period the death rate for males aged 65-69 years declined by more than 50%, and a similar pattern was evident for females (table 9.6). The shift in the age of death is highlighted by the fact that in 1908 approximately 30% of all deaths occurred in persons aged 65 years or more, but by 1998 this percentage had increased to nearly 78% of all deaths.
The decline in infectious diseases, particularly in the younger age groups, was the driving force behind the decline in mortality in the first half of the 20th century. In 1908 infectious diseases comprised approximately 25% of all deaths for both males and females; the death rate for males from infectious diseases was 300 per 100,000 persons, and for females 233. In 1920 three of the leading causes of death for children under five years of age were infectious diseases: diarrhoea and enteritis; diptheria; and measles (United Nations 1982). By 1998 infectious diseases comprised approximately 1% of all deaths.
As in other developed countries, infectious diseases in Australia declined following World War I and degenerative diseases began to rise, in particular diseases of the circulatory system (Omran 1971). Graphs 9.7 and 9.8 show the emergence and dominance of diseases of the circulatory system for both males and females, although the impact was greater for males. The age-standardised death rate for diseases of the circulatory system peaked for males in the late 1960s at 843 per 100,000 persons, and for females in the early 1950s at 558 per 100,000 persons. Since the 1970s the death rate for diseases of the circulatory system declined rapidly, mainly due to changes in lifestyle and improvements in the management of the disease (AIHW 2000). By 1998 the death rate for this group of diseases had declined to 285 for males and 188 for females per 100,000 persons.
The age-standardised death rate for cancer among males increased from 132 per 100,000 persons in 1908 to 217 in 1998; for females it decreased marginally from 138 per 100,000 persons in 1908 to 131 in 1998. However, as a proportion of all deaths, cancer deaths increased significantly during the 20th century. In 1908 cancer accounted for 6% of all male deaths and 7% of female deaths. By 1998 this proportion of all deaths had increased to approximately 25% for both males and females. Paradoxically, a greater proportion of cancer deaths in a population often reflects the higher longevity of that population, because cancer is predominantly a disease of the elderly.
1 In 1997 the ABS introduced an automated system for coding causes of death. As the system was developed in the United States, it uses the US interpretation of the International Classification of Diseases Version 9 (ICD-9) coding rules for identifying the underlying cause of death. That interpretation, in some instances such as pneumonia, differs significantly from the interpretation of the rules previously used in Australia.
Australian Institute of Health and Welfare 2000, Australia's Health 2000: the seventh biennial health report of the Australian Institute of Health and Welfare, AIHW, Canberra.
Olshansky, S.J. and Ault, A.B. 1986, "The fourth stage of the epidemiologic transition: the age of delayed degenerative diseases", The Milbank Quarterly, Vol. 64, No. 3, 1986.
Omran, A.R. 1971, "The epidemiologic transition, a theory of the epidemiology of population change", The Milbank Quarterly, Vol. 49, No. 4, 1971, Part 1.
United Nations 1982, Country monograph series No.9, Population of Australia, volume 1, Economic and Social Commission for Asia and the Pacific, Bangkok, Thailand.
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