The changing face of the Australian population: growth in centenarians

Centenarians are defined as people who have reached the age of 100 years. Among Australia’s centenarians in 2001, 93% were aged 100–104 years, 6.3% were aged 105–109 years (“semi-supercentenarians”) and 0.3% were aged 110 years and over (“supercentenarians”).4 No data for later years exist.

From 1901 to 1971, the proportion of centenarians in the Australian population ranged from 0.0013% to 0.0016%. However, from 1971, the proportion of centenarians almost doubled every decade to reach 0.012% in 2001, and is on track to double again in the next decade (Box 1). Australia is among the countries that have the highest proportion of centenarians, along with the United States, Norway, and the island of Sardinia in Italy (information from unpublished census data, made available on request from the Australian Bureau of Statistics [ABS], 2007, and from McCormack12).

Among the 3154 centenarians recorded in the 2006 Census, 1058 were in New South Wales, 823 in Victoria, 538 in Queensland, 308 in South Australia, 310 in Western Australia, 73 in Tasmania, and 44 in the Northern Territory and Australian Capital Territory (information from unpublished census data, made available on request from the ABS, 2007).

Life expectancy is a frequently used indicator of the health of a population.13 Corresponding to the increase in the proportion of centenarians in the Australian population is the increasing life expectancy at birth (78.5 years for males and 83.3 years for females in 2006) (Box 1).

Over the past 59 years, the number of people in younger age groups has fallen as a proportion of the Australian population, and annual growth rates have declined in under-30s age groups (Box 2). Over the same period, growth rates in the middle-age segments have remained steady, whereas growth rates in the 80–99-year and ≥ 100-year age groups have increased. The centenarian group has experienced the fastest growth rate (8.5% per year over the past 25 years).11,14-16

Over half the centenarians recorded in the 2001 Census were born in Australia, a third in other countries, and the remainder did not identify a birthplace.4 The proportion of overseas-born people is significantly higher among centenarians than in the total Australian population, with only 22% of the population reported as being overseas-born in the 2001 Census.17

In the early 1900s, 60% of centenarians were men and 40% were women (Box 1). A hundred years later, this ratio has reversed, with women predominating at 75% in 2006. There were also significant differences in marital status between male and female centenarians and between centenarians and people aged ≥ 85 years at the 2001 and 2006 censuses (Box 3) (information from unpublished census data, made available on request from the ABS, 2007). A higher proportion of centenarian men than women were currently married: 19% of men versus 5% of women in 2001 and 28% of men versus 9% of women in 2006. Half of men aged ≥ 85 years were currently married, compared with 12% of women. A higher proportion of centenarian men had never married (32% in 2001 and 26% in 2006) compared with women (13% in 2001 and 12% in 2006). Female centenarians were more likely than male centenarians to be widowed (76% v 34%, respectively, at the 2001 Census) (information from unpublished census data, made available on request from the ABS, 2007).

In 2001, 79% of male and 38% of female centenarians were living in private dwellings — with a partner, other family member(s) or alone — rather than in nursing homes or other residential aged care facilities;4 27% of male centenarians and 14% of female centenarians were living alone in their own homes. The differences between men and women may partly be explained by a phenomenon observed in the New England Centenarian Study: men who live to 100 years are fewer in number, but generally healthier and with less dementia, than female centenarians,18 and are thus more likely to be able to function independently in their own homes. The New England Centenarian Study refutes the paradigm that the older you get the sicker you become, instead providing evidence to support the concept of “compression of morbidity” into a shorter time span — the older you get, the healthier you have been.18

First, there has been a major change in Australia’s fertility rate. Since the 1960s, there has been a steady decline in fertility rate, resulting in a slow population growth in the younger age groups.13 Fertility rates have fallen below the replacement level of 2.1 children per woman for the past 25 years, a pattern observed in other developed countries.19 Decreased fertility rate is also related to an increase in the age of mothers at the birth of their first child (the median maternal age at first birth is 30–34 years). The decline in fertility rate has a major impact on the age structure of the population.13 The health of all Australians, including pregnant women, has improved dramatically over the past decades with reductions in morbidity and mortality related to chronic and communicable diseases and reductions in injuries.13

Second, there has been an increase in survival rates of sick people, with slower progression of some chronic diseases and improvement in health status and lifestyle indicators of older people, leading to a compression of morbidity.20 Declining mortality has resulted in significant increases in the number of old people.

Forty to 50 years ago, the age structure of the Australian population was pyramid-shaped, with the largest proportion of the population in the younger age groups and the older age groups at the apex. However, by 2006 the demographic transition had resulted in the pyramid shape changing to a beehive shape, with more older people and fewer younger people.13

Since 1901, life expectancy has increased by around 42%, with reductions in infant, child and maternal mortality being the major contributors.13,21 Australia has the fourth highest life expectancies for men and women in the world, behind Japan, France and Italy, but ahead of Sweden, Switzerland, Spain, Canada, Singapore, New Zealand, Norway, the United Kingdom and the US.13,22

The demographic transition we now see in Australia is characterised by an ageing population. Retired people aged 50–74 years contribute increasingly to the long-term care of their very elderly parents and in-laws (aged 85 years and over), as well as playing a pivotal role in the lives of their grandchildren and children, thus creating an effect on intergenerational relationships.23,24 These family members are untrained and unmonitored caregivers, with the burden falling disproportionately on women.25

The fact that 27% of male and 14% of female centenarians live alone hardly depicts these very old people as being totally frail and dependent (although some very old people receive assistance within the home). Furthermore, increased longevity does not necessarily equate with a higher prevalence of disability. Indeed, several studies have shown that disability and physical limitations in older people are decreasing.26,27 Health-based projections of US populations have reported a significant downward revision in estimates of the proportion of elderly people with chronic disabilities.26,27

However, there is a complex relationship between disability and the use of acute care, as longer life prompts greater spending on restorative procedures to enhance mobility, such as hip replacements and removal of cataracts.26 Reported reductions in disabilities reflect changes that have made physical environments more manageable, such as modifications in the home. These include grab bars, raised toilets, telephones with amplifying devices and touchtone dialling, and wider use of hearing aids. Such devices can lead to improvements in health.26

Australia belongs to a group of countries that have the highest proportion of long-lived people. Many Australians are unaware of how many centenarians there are and how little we know about them. It is amazing that these extremely enduring old people whose lives carry a wealth of history are living among us and yet we appear to have largely ignored their effect on our society. Indeed, while there are government initiatives to meet the requirements of an ageing population (Box 4), we have no specific social or financial estimates of the impact of the oldest old in Australia, and have developed few specifically targeted policies.

The demographer Vaupel claims that females born today in low-mortality countries like France already have a 50% chance of living to 100 years.30 We can project a similar situation in Australia as the growth rate of centenarians continues to increase. It is estimated that there will be 12 000 centenarians in Australia by 2020, and 50 000 by 2050; and the number of centenarians worldwide is estimated to increase 15-fold, to 2.2 million, by 2050.31

An ageing population is much more than just a demographic statistic and has major implications for health care. Improving the level of functioning of our very old Australians and preventing disabilities is important. Yet we know very little about centenarians. Studies are necessary to monitor and assess the oldest old, so that realistic public health policies and evidence-based resources can be developed to enable as many centenarians as possible to continue living independently in their homes and within our communities.

Currently, 16% of Australians are aged 60 years and over (Box 2). However, if the ageing pattern in Australia follows that of the US, we can expect that, as baby boomers age, the proportion of Australians reaching the age of 85 or over will rise from the current 2% of the population to around 5% by 2050.32 The consequences of the demographic transition need investigation by health policymakers and economists — we need a better understanding of changes in prevalence of disability in order to make estimates of the likely short- and long-term cost implications.