Chronic diseases mortality

Chronic diseases are large contributors to mortality. Their relative contribution has increased over the last several decades. Figure 1 shows the changing pattern of mortality over the last 100 years in Australia. 

Figure 1: Trends in major causes of deaths in Australia, 1907 to 2006

Source: AIHW Mortality Database.

Many people with a chronic disease often die of another chronic disease. Therefore chronic disease mortality should be considered in terms of both underlying and associated causes. The underlying cause is the one that initiates the sequence of events leading to death, whereas an associated cause contributes to the set of events leading up to death. 

In 2006, the set of 12 chronic diseases included on this website were listed as the underlying cause for almost half of all deaths in Australia.  Six of those chronic diseases - coronary heart disease (CHD), stroke, lung cancer, chronic obstructive pulmonary disease (COPD) colorectal cancer and diabetes- were among the top ten underlying causes of death. Coronary heart disease was the top of the list, followed by stroke (Table 1). 

CHD and stroke were also listed frequently as associated causes of death along with chronic kidney disease and diabetes. Lung cancer and colorectal cancer were listed less often as associated causes.

Premature death caused by chronic diseases can be measured by potential years of life lost (PYLL), which counts the number of years of life lost for each death before the age of 75 years. A person dying at 55 is considered to have lost 20 years of potential life. Death due to these chronic diseases were responsible for an estimated 253,209 PYLL, representing nearly one third of PYLL for all causes in Australia. Coronary heart disease was the largest single contributor to PYLL.

Note: *Suicide is used here as an indicator for depression related mortality, since it is commonly associated with depression. 
Source: AIHW National Mortality Database.

Coronary heart disease

CHD, sometimes also referred to as Ischaemic heart disease (ICD-10 I20-I25) accounted for 22,983 deaths (17% of all deaths) in Australia in 2006. It was also listed most frequently as an associated cause in 21,848 deaths.

The death rate for CHD climbed steadily from the 1940s, peaking in 1968 (Figure 2). The rates have declined annually by 3.8% for males and 3.6% for females since then, to 133 and 77 per 100,000 for males and females respectively in 2006. Male CHD death rates in Australia have consistently been nearly twice those of females, a finding common to most Western societies.

Figure 2: Trends in death rates for coronary heart disease in Australia, 1940 to 2006

Note: Rates are age-standardised to the 2001 Australian population.
Source: AIHW National GRIM Books.

Stroke

Stroke (ICD-10 I60-I64) claimed 8,484 lives (6% of all deaths) in Australia in 2006. Stroke was also reported as an associated cause in 7,951 deaths. 

The death rates were 37 per 100,000 for both males and females. These rates are less than one-third the prevailing rates three decades earlier, reflecting a progressive decline over that period (Figure 3). The declines in stroke death rates are similar to those for CHD. Unlike CHD, there is much less difference in the rates between the sexes. The stroke death rate for males has consistently been about 10% higher than the rate for females, while for CHD the male rate has always been about double the female rate.

Figure 3: Trends in death rates for stroke in Australia, 1979 to 2006

Note: Rates are age-standardised to the 2001 Australian population.
Source: AIHW National GRIM Books.

Lung cancer

Lung cancer (ICD-10 C33-C34) is the fourth-largest cause of death overall in Australia, surpassed only by deaths from coronary heart disease, stroke and other heart diseases. In 2006, there were 7,348 deaths from lung cancer (4,665 males and 2,683 females), a death rate of 34 per 100,000 population.

Lung cancer death rates in Australia are declining overall. The decline is mainly due to reduction in death rate among males, from 80 per 100,000 in 1982 to 47 per 100,000 in 2006 (Figure 4). In contrast, the lung cancer death rate among females has continued to increase (from 16 per 100,000 in 1982 to 23 per 100,000 in 2006). 

Trends in lung cancer death rates largely reflect smoking trends, with a time lapse of about 20 years. As overall tobacco consumption has declined, mortality from lung cancer has followed. For example, the male smoking rate started to fall decades ago and the benefits have had time to flow through. For females, the fall in smoking has been too recent to show this benefit and the female lung cancer death rate is still rising.

Figure 4: Trends in death rates for lung cancer in Australia, 1945 to 2006

Note: Rates are age-standardised to the 2001 Australian population.
Source: AIHW National GRIM Books.

Colorectal cancer

Colorectal cancer (CRC) (ICD-10 C18-C21) is the third most common cause of cancer deaths among males after lung and prostate cancer and  the fourth most common cause of cancer among females after breast and lung cancer, and cancers of unkown primary site. There were 3,858 deaths (2,149 males and 1,709 females) from CRC in 2006, with a death rate of 18 per 100,000.

Since 1950, the male death rate for CRC remained fairly steady until the mid 1980s, and then declined from 32 per 100,000 in 1983 to 22 per 100,000 in 2006 (Figure 5). The female death rate on the other hand showed a steady decline over this period. The reasons for these declines are not clear, but may be due to a combination of better diet and some use of screening.

Figure 5: Trends in death rates for colorectal cancer in Australia, 1921 to 2006

Note: Rates are age-standardised to the 2001 Australian population.
Source: AIHW National GRIM Books.

Depression

While the major impact of depression is in terms of morbidity and disability, depression is a factor commonly associated with suicide (ICD-10 X60-X84) and attempted suicide. Suicide claimed 1,799 lives (1.3% of all deaths) in Australia in 2006 and was the second largest contributor to PYLL that year, because many suicide deaths occur at younger ages. 

Suicide death rates for females have been relatively stable, at around 5 per 100,000, over the past century. The period 1962-72 was an exception, when the rates were higher, peaking at 13 per 100,000 in 1967. Male rates have been much higher over the century and also have fluctuated more. From a low of 12 per 100,000 in 1944, the male rates increased steadily, peaking at 25 per 100,000 in 1963. During the 1970s the rates were stable at around 18 per 100,000, before climbing again to 24 per 100,000 in 1997. In 2006, the rate had declined again, to 14 per 100,000 (Figure 6).

Figure 6: Trends in death rates for suicide in Australia, 1907 to 2006

Note: Rates are age-standardised to the 2001 Australian population.
Source: AIHW National GRIM Books.

Diabetes

Diabetes (ICD-10 E10-E14, which covers both Type 1 and Type 2 diabetes mellitus) is the ninth leading underlying cause of death among Australians. It is also mentioned frequently as an associated cause of death, particularly where cardiovascular disease is the underlying cause of death. In 2006, diabetes was listed as an underlying cause in 3,662 deaths (2.7% of all deaths) and as an associated cause in 9,203 deaths.

Trends over the past half century indicate that diabetes death rates in males are now higher than in 1950, but lower than their peak in 1968 (Figure 7). In females, the diabetes death rates are now about half the level they were in 1950, and well below those for males. 

Figure 7: Trends in death rates for diabetes in Australia, 1907 to 2006

Note: Rates are age-standardised to the 2001 Australian population.
Source: AIHW National GRIM Books.

Asthma

Asthma (ICD-10 J45-J46) is less frequently listed as an underlying cause of death compared to most other chronic diseases. However, it is about 2 times more frequently listed as an associated cause of death. Across all ages in 2006, there were 402 deaths from asthma as an underlying cause, 0.3% of all deaths in that year.

There was a rise in deaths directly attributed to asthma during the early to mid-1980s, reaching a peak in 1989 with 736 deaths, with a subsequent steady decline (Figure 8). After 1992, death rates were higher in females than males in the population as a whole.

Figure 8: Trends in death rates for asthma in Australian, 1979 to 2006

Note:  Rates are age-standardised to the 2001 Australian population, and pre 1997 data adjusted to ICD10 standards using comparability factor 0.75.
Source: AIHW National GRIM Books.

Chronic obstructive pulmonary disease

COPD (ICD-10 J41-J44) accounted for 4,761 deaths (3.6% of all deaths) in Australia in 2006. It was also listed  as an associated cause in 7,456 deaths. It was the sixth leading cause of death among males (31 per 100,000) and seventh most common cause of death among females (16 per 100,000).

Due to its strong link with smoking, the levels and trends in death rates for COPD are similar to those for lung cancer (Figure 9). In Australia, the death rate attributable to COPD increased steadily from the 1950s, peaking in the early 1970s. Since 1970 the male death rate for COPD has, in general, decreased, but the female death rate has only decreased since 1996.

Figure 9: Trends in death rates for COPD in Australia, 1922 to 2006 

Note: Rates are age-standardised to the 2001 Australian population.
Source: AIHW National GRIM Books.

Chronic kidney disease

Chronic kidney disease (CKD) is a common cause of death, responsible for 2,705 deaths in 2006 (2.0% of all deaths in Australia in that year). In addition, CKD was listed on death certificates as an associated cause in a further 10,956 deaths.  

Mortality from CKD in Australia decreased slowly since 1979, with some fluctuations. The death rate for CKD in 2006 was 15 per 100,000 males and 10 per 100,000 females (Figure 10).

Figure 10: Trends in death rates for chronic kidney disease in Australia, 1979 to 2006

Note: Rates are age-standardised to the 2001 Australian population.
Source: AIHW National GRIM Books.

Oral diseases

Most oral diseases are not life threatening except for oral cancers (ICD-10 C00-C14). In 2006, there were 613 deaths (0.5% of all deaths) from oral cancer. 

The female death rate for oral cancer has been stable over the past century at about 2 per 100,000. The male rate in the early part of the 20 century was around 25 per 100,000, but then declined steadily to 6 per 100,000 in 1958 and has remained at that level (Figure 11). 

Figure 11: Trends in death rates for oral cancer in Australia, 1907 to 2006

Note: Rates are age-standardised to the 2001 Australian population.
Source: AIHW National GRIM Books.

Arthritis

Arthritis results in relatively few deaths. In 2006, there were 77 deaths from arthrosis, also called osteoarthritis (ICD-10 M15-M19) and 169 deaths from rheumatoid arthritis (ICD-10 M05-M06). Historically, females have higher numbers of deaths from arthritis than males.

Figure 12: Trends in death rates for arthritis in Australia, 1979 to 2006

Note: Rates are age-standardised to the 2001 Australian population.
Source: AIHW National GRIM Books.

Osteoporosis

Only a small number of deaths were coded to osteoporosis (ICD-10 M80-M82) as an underlying cause (28 for males and 171 for females in Australia in 2006). However, many more deaths were coded to hip fracture, which are most likely caused by osteoporosis. 

Further information

For more information on mortality trends see Trends in Deaths: Analysis of Australian Data 1987-1998 with updates to 2000 and Australia's Health 2008.