Over the past century, the world has seen unprecedented declines in mortality rates, leading to an accelerated increase in the world population. This century will realise falling fertility rates alongside ageing populations. The 20th century was the century of population growth; the 21st century will be remembered as the century of ageing. Increase in life expectancy is one of the highest achievements of humankind; however, ageing and age-related disease is a mounting challenge for individuals, families, and for social, economic, and healthcare systems. Since healthy life expectancy has lagged behind the increase in life expectancy, the rise in morbidity will increase the burden on healthcare systems. Implementation of preventive health strategies to decrease, delay or prevent frailty, lung, breast and colon cancer, cardiovascular disease, metabolic syndrome, osteoporosis and osteopaenia, may increase health expectancy, and permit women to age gracefully and maintain independent living, without disability, for as long as possible.
Introduction
A growing world
Human populations grew at about 0.05% annually for 10,000 years such that, by the year 1500, the global population was around 400 million people. A significant increase in population growth occurred in the 17th and 18th centuries, with the growth rate increasing to about 0.5% annually and reaching 1 billion at the start of the 19th century. The population growth rate continued to increase to 0.7% after 1900, and to 2% in the 1960s, with 1.6 billion worldwide in the beginning of the 20th century. By the year 2000, 6.1 billion people inhabited our planet. The United Nations projects that, by 2100, the world population will reach 11.5 billion people, an increase of almost 5 billion people between 2000 and 2100.
The four most important elements in determining population growth and ageing in any country or region are fertility rate, life expectancy, migration, and emigration.
Women’s role in society has changed. They have more access to education and greater choice in careers; childcare outside of the home is associated with a decrease in fertility rate. Improvements in healthcare are one of the important factors increasing life expectancy. Population ageing is a direct result of the decrease in the fertility rate and the increase in life expectancy. Migration within and emigration from a country or region are the most important factors affecting demographic change; however, as mostly younger people migrate or emigrate, this will influence the ageing pattern of these countries ( Fig. 1 ).
Immigration has increasingly become perceived as a potential means of preventing population decline, maintaining a sufficient labour force and support ratio, and thus slowing down structural population ageing. In particular, immigration has a potentially strong and long-lasting affect on population growth and composition through the interaction among the number of migrants, their relatively younger age, and their higher fertility, according to Harper. Uncontrolled immigration could, however, result in demographic changes that may influence social, cultural, and economic stability, and may lead, in extreme conditions, to discontent.
The increase in world population from 1.6 billion in 1900 to 6.1 billion in 2000 arose primarily from population growth in less developed countries that experienced a significant increase in life expectancy. While rising life expectancy occurred over centuries in Europe, many less developed countries accomplished it in decades. As growth rates in less developed countries rose to levels never experienced in more developed countries, many countries implemented policies to lower the birth rate to adjust for rapidly declining death rates, especially related to lower rates of perinatal and infant mortality. Although some less developed countries had dramatic declines in birth rates, others had a somewhat more gradual decline, and some experienced almost no decline at all.
Overall, the total fertility rate in less developed countries declined from about 6.0 in the early 1950s to about 2.5 today, a much more rapid decrease than that of Europe from 2.5 in 1960 to 1.5 in 2011, and North America from 3.7 in 1960 to 2.1 in 2011. Thus, although less developed countries continue to have population growth, the EU27 countries, in particular, will see population shrinkage of around 0.2% per year between 2020 and 2045. Italy and Germany will be particularly affected, with projected falls from 60 million to 57 million in Italy between 2010 and 2050, and 82 million to 79 million for Germany. Italy will need to raise its retirement age to 77 or admit 2.2 million young immigrants annually to maintain its worker to retiree ratio, at the expense of a significant change in its demography.
The past century has witnessed a transition from a high mortality and high fertility pattern to one of historically unprecedented declines in mortality rates followed by equally unprecedented declines in fertility rates. This change has resulted in a rapidly ageing world population. The 20th century was the century of population growth; the 21st century will be remembered as the century of ageing.
In 2010, the world population has reached a transition point. The rapid growth of the second half of the 20th century has slowed, but factors such as continuously increasing longevity and slower-than-expected declines in birth rates, guarantee continued growth for decades.
Life expectancy
Humans had a life expectancy of about 30 years for about 99.9% of the time we inhabited this planet ( Fig. 2 ). Today, in developed countries, more than 75% die after the age of 75 years. In the record-holding country, Japan, female life expectancy was 86 years in 2007, surpassing the 85-year limit to human life expectancy proposed by Fries et al.
In 1900 in Europe, life expectancy was around 45 years, and health expectancy, the ability to live independently, was similar between men and women since one died within days, weeks or months from infectious diseases. Life expectancy estimates reflect how many years a person might be expected to live. Healthy life expectancy is an estimate of how many years they might live in ‘good health and without disability’. Most babies born after 2000 in countries with long-lived residents will celebrate their 100th birthdays if the present yearly increase in life expectancy continues through the 21st century.
Death rates fell substantially, well before any effective treatment or immunisation was developed. Probably, life-style changes owing to improved sanitation, hygiene and better nutrition contributed to longer life. Advances in the understanding of contagion and infection contributed toward eradication of typhoid and cholera. Hence, public health projects such as sewage and water systems, and better housing and working conditions, helped stop typhoid and diarrhoea and prolong life generally ( Fig. 3 ).
Between the years 1900 to 2000, these public health preventive strategies as well as vaccination and medical advances, such as antibiotics, increased life expectancy; and non-communicable diseases became the main cause of mortality. Even today, more than 2.6 billion people (about 39% of the world’s population) still do not have access to improved sanitation facilities. Sexually transmitted infections (STI), such as chlamydia, contribute to infertility, and human immunodeficiency virus leads to a significant reduction in quality of life, with individual suffering and an extreme cost to society. These diseases could be prevented to a large extent by proper sex education and use of condoms.
In all countries worldwide, poverty is the single greatest obstacle to a secure old age. In less developed countries, the problems associated with old age are poor diet, ill-health and inadequate housing, which are all exacerbated by poverty. Furthermore, because of changes in lifestyles in the developing world, chronic illness is becoming endemic among many older people, because technical advances in medicine have far outrun social and economic development that allows for relatively disease-free living.
Populations in developed countries, by and large, have passed from infectious and parasitic diseases to chronic degenerative diseases. Death from metabolic and degenerative disease increased the gap between male and female mortality by 5–7 years, and between health expectancy and life expectancy in men by 5–7 years, and in women by 7–9 years in most developed countries ( Fig. 4 ). Although women experience greater burdens of morbidity and disability, men die earlier, yet the reasons for such premature mortality are not fully understood ( Table 1 ). Health and life expectancy estimates are based on country life tables, analyses of 135 causes of disability for 17 regions of the world and 69 health surveys in 60 countries. The estimates of health expectancy are more uncertain than those for life expectancy, because it is difficult to ensure comparable measurements of disability across countries. Because health is a multidimensional notion, several indicators are needed to capture trends. According to Verbrugge and Jette, health deterioration can be described by risk factors that lead to diseases and conditions that can cause loss of function and, depending on the environmental context, can result in transition from good health to disability, frailty, and mortality.
| Country | Life expectancy male versus female years (years beyond males) | Health expectancy male versus female years (years lost to debility) | ||
|---|---|---|---|---|
| Male | Female | Male | Female | |
| Japan | 79 | 86 (7) | 73 (6) | 78 (8) |
| Monaco | 78 | 85 (7) | 71 (6) | 76 (8) |
| France | 77 | 85 (7) | 71 (6) | 76 (9) |
| Austria | 77 | 83 (6) | 70 (7) | 74 (9) |
| Germany | 77 | 82 (5) | 71 (6) | 75 (7) |
| USA | 76 | 81 (5) | 73 (6) | 78 (8) |
| China | 72 | 75 (3) | 75 (6) | 78 (8) |
| Russian Federation | 60 | 73 (7) | 55 (5) | 65 (7) |
| South Africa | 52 | 55 (3) | 47 (5) | 48 (7) |
a On the left side of the table, the age of male life expectancy is listed in years by country. In the next column, the female life expectancy is listed with the number of years women live beyond males in parentheses. On the right side of the table, the expected age of healthy life expectancy for both males and females is listed with the number of years of frailty and disability in parentheses.
Ageing successfully would show minimal declines in physiologic function, whereas those ageing ‘poorly’ would show disease-related decrements and loss of reserve capacity, commonly interpreted as the effects of age. The increased gap between health expectancy and life expectancy, however, may be partly due to improved medical knowledge and health-service use in elderly people, without changes in underlying conditions. For instance, initially silent diseases, such as type 2 diabetes, hypertension, and some cancers, now are diagnosed and receive better treatment earlier than previously. This progress leads to a longer period of morbidity, but an improved functional status. A rise in prevalence of chronic diseases, including heart disease, arthritis, and diabetes, was recorded in elderly people between the 1980s and 1990s in the USA and in 12 Organization for Economic Co-operation and Development countries. This increased prevalence may reflect an increase in life expectancy with an increase in the ageing population.
Life expectancy
Humans had a life expectancy of about 30 years for about 99.9% of the time we inhabited this planet ( Fig. 2 ). Today, in developed countries, more than 75% die after the age of 75 years. In the record-holding country, Japan, female life expectancy was 86 years in 2007, surpassing the 85-year limit to human life expectancy proposed by Fries et al.
In 1900 in Europe, life expectancy was around 45 years, and health expectancy, the ability to live independently, was similar between men and women since one died within days, weeks or months from infectious diseases. Life expectancy estimates reflect how many years a person might be expected to live. Healthy life expectancy is an estimate of how many years they might live in ‘good health and without disability’. Most babies born after 2000 in countries with long-lived residents will celebrate their 100th birthdays if the present yearly increase in life expectancy continues through the 21st century.
Death rates fell substantially, well before any effective treatment or immunisation was developed. Probably, life-style changes owing to improved sanitation, hygiene and better nutrition contributed to longer life. Advances in the understanding of contagion and infection contributed toward eradication of typhoid and cholera. Hence, public health projects such as sewage and water systems, and better housing and working conditions, helped stop typhoid and diarrhoea and prolong life generally ( Fig. 3 ).
Between the years 1900 to 2000, these public health preventive strategies as well as vaccination and medical advances, such as antibiotics, increased life expectancy; and non-communicable diseases became the main cause of mortality. Even today, more than 2.6 billion people (about 39% of the world’s population) still do not have access to improved sanitation facilities. Sexually transmitted infections (STI), such as chlamydia, contribute to infertility, and human immunodeficiency virus leads to a significant reduction in quality of life, with individual suffering and an extreme cost to society. These diseases could be prevented to a large extent by proper sex education and use of condoms.
In all countries worldwide, poverty is the single greatest obstacle to a secure old age. In less developed countries, the problems associated with old age are poor diet, ill-health and inadequate housing, which are all exacerbated by poverty. Furthermore, because of changes in lifestyles in the developing world, chronic illness is becoming endemic among many older people, because technical advances in medicine have far outrun social and economic development that allows for relatively disease-free living.
Populations in developed countries, by and large, have passed from infectious and parasitic diseases to chronic degenerative diseases. Death from metabolic and degenerative disease increased the gap between male and female mortality by 5–7 years, and between health expectancy and life expectancy in men by 5–7 years, and in women by 7–9 years in most developed countries ( Fig. 4 ). Although women experience greater burdens of morbidity and disability, men die earlier, yet the reasons for such premature mortality are not fully understood ( Table 1 ). Health and life expectancy estimates are based on country life tables, analyses of 135 causes of disability for 17 regions of the world and 69 health surveys in 60 countries. The estimates of health expectancy are more uncertain than those for life expectancy, because it is difficult to ensure comparable measurements of disability across countries. Because health is a multidimensional notion, several indicators are needed to capture trends. According to Verbrugge and Jette, health deterioration can be described by risk factors that lead to diseases and conditions that can cause loss of function and, depending on the environmental context, can result in transition from good health to disability, frailty, and mortality.
| Country | Life expectancy male versus female years (years beyond males) | Health expectancy male versus female years (years lost to debility) | ||
|---|---|---|---|---|
| Male | Female | Male | Female | |
| Japan | 79 | 86 (7) | 73 (6) | 78 (8) |
| Monaco | 78 | 85 (7) | 71 (6) | 76 (8) |
| France | 77 | 85 (7) | 71 (6) | 76 (9) |
| Austria | 77 | 83 (6) | 70 (7) | 74 (9) |
| Germany | 77 | 82 (5) | 71 (6) | 75 (7) |
| USA | 76 | 81 (5) | 73 (6) | 78 (8) |
| China | 72 | 75 (3) | 75 (6) | 78 (8) |
| Russian Federation | 60 | 73 (7) | 55 (5) | 65 (7) |
| South Africa | 52 | 55 (3) | 47 (5) | 48 (7) |
a On the left side of the table, the age of male life expectancy is listed in years by country. In the next column, the female life expectancy is listed with the number of years women live beyond males in parentheses. On the right side of the table, the expected age of healthy life expectancy for both males and females is listed with the number of years of frailty and disability in parentheses.
Ageing successfully would show minimal declines in physiologic function, whereas those ageing ‘poorly’ would show disease-related decrements and loss of reserve capacity, commonly interpreted as the effects of age. The increased gap between health expectancy and life expectancy, however, may be partly due to improved medical knowledge and health-service use in elderly people, without changes in underlying conditions. For instance, initially silent diseases, such as type 2 diabetes, hypertension, and some cancers, now are diagnosed and receive better treatment earlier than previously. This progress leads to a longer period of morbidity, but an improved functional status. A rise in prevalence of chronic diseases, including heart disease, arthritis, and diabetes, was recorded in elderly people between the 1980s and 1990s in the USA and in 12 Organization for Economic Co-operation and Development countries. This increased prevalence may reflect an increase in life expectancy with an increase in the ageing population.
An ageing world
Improved health care, increased access to education, and economic growth, has led to longer life expectancy in every region and across most socioeconomic groups. The proportion of elderly population has been rising and will continue to grow from 8% (551 million people over 65 years) in 2010 to 21% (1964 million people over 65 years) by 2050. The projected two billion elderly people of the year 2050 are already around us as teenagers and young people.
Seventy per cent of all older people now live in low or middle-income countries. Population ageing is also occurring much faster in these countries. These countries have a much briefer opportunity to build the infrastructure necessary to address this demographic trend. The amount of growth and ageing these developing countries experience, however, depends upon the degree to which mother and child health services are able to decrease maternal, neonatal and child mortality. Couples who have access to family planning and health services might choose to reduce family size, raising fewer, but healthy children.
Although this shift to increased life expectancy and decreased fertility rates represents a major global success story, ageing populations also present challenges to families, communities, and countries. This demographic shift is unprecedented in world history, and is most likely irreversible. Not only is the world’s population becoming older, the older are living longer. Those aged 80 years and older are the most rapidly growing age group worldwide. The population of centenarians in 2050 will be 16 times larger than in 2000 (2.2 million compared with 135,000) with the male-to-female ratio of centenarians falling to about 1:4. To maintain current standards of living in more developed countries, and to improve prospects for those in less developed countries, countries must include and involve older populations as productive and active contributors to society. A larger, dependent and elderly population will place greater financial demands on the working population and governmental budgets.
The trend towards breakdown of extended families, changing lifestyles, and emigration from rural to urban areas has forced elderly people to live alone. The family network was often the only form of welfare and support for elderly people. Now, old people are often considered a family burden. The processes of social change, such as industrialisation, urbanisation, and migration often have a negative effect on care for elderly people, particularly in rural areas.
Life course perspective
The life course perspective considers the gap between onset of debilitating illness and death, and illustrates that women die after the age of 80 years in many regions in the world mostly from non-communicable diseases ( Fig. 4 ). This life course perspective leads to important policy and strategy decisions. Cross-sectional studies show differences in mortality and morbidity as a function of socioeconomic status, across various disease categories throughout the life span. Ageing successfully would show minimal declines in physiological function, whereas those ageing ‘poorly’ would show disease-related decrements and loss of reserve capacity, commonly interpreted as the effects of age. We propose six components of successful ageing, namely: (1) avoidance of risk factors for disease (hygiene, absence of smoking and limiting excessive use of alcohol); (2) active engagement (social and emotional health); (3) optimal nutrition; (4) physical activity; (5) retaining a high level of cognitive function (by engaging in cultural and intellectual activity) and (6) periodic medical and laboratory exams and screening methods to early detect and treat any pathological processes ( Fig. 5 ).
Poverty significantly affects life and health expectancy. It should be measured in terms of property, employment, wages and income, and also in terms of basic education, healthcare, nutrition, water and sanitation. Educational level and marital status have also been shown in several longitudinal studies to be powerful predictors of morbidity, health expectancy, and mortality.
The economic consequences of retirement place many older citizens in positions of financial vulnerability. As populations age in the developing and the developed worlds, the issue becomes how to keep older persons economically viable within their respective societies. No community is exempt from the financial hardships experienced by ageing populations.
It is clearly possible (and indeed desirable) to improve the health status of women and men when they are old. Yet, a complementary approach to improving the health of older people would focus on appropriate interventions from a much earlier age in order to prevent frailty, which is now seen as a multi-system disorder and one of the central geriatric syndromes. Frailty can be triggered by multiple pathophysiological processes such as malnutrition, hormonal imbalances, chronic inflammation, and multimorbidity. Frailty often leads to deterioration of health status, immobilisation, disability and death, and is particularly characterised by a reduced functional reserve and increased vulnerability to internal and external stressors. Frailty imposes, therefore, an increased risk on older people to recover inadequately from even minor events such as gastroenteritis or change of residence.
The increasing number of frail older people will seriously challenge the healthcare system because primary care for these patients is currently fragmented, time consuming and reactive. To preserve functional performance and maintain independent living in this vulnerable population, a transition is needed towards more proactive, integrated, and structured health care for older people.
Life-history studies of childhood and adolescence demonstrate clearly that social factors probably operate in a cumulative fashion. Significant social class differences exist in attaining height and other aspects of physical development, as well as in incidence of infectious and other diseases, and risk of injury. In early life and childhood, primary prevention strategies include a healthy lifestyle and proper nutrition to build functional capacity to a maximum and adhering to vaccination schedules.
During adult life, and at older age, the goal is to maintain the highest possible level of functioning through continuing a healthy life-style with proper nutrition, physical and mental exercise, and preventive strategies to detect and treat any pathological processes early. With a better understanding of the biology of the ‘front end’ of chronic disease, the emphasis has shifted from the preventive care of women in their middle years to include that of younger women. Over time, ageing in health and with dignity through the practice of preventive ambulatory care will begin in infancy and, in the future, may start before conception.
Thus, the goal of preventive medicine is to keep the ageing population productive and as healthy as possible, hopefully reducing the length of time in which their health and functionality are compromised before death. The ultimate goal being ‘ageing in health and with dignity.’
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