Elsevier

The Lancet

Volume 374, Issue 9696, 3–9 October 2009, Pages 1196-1208
The Lancet

Review
Ageing populations: the challenges ahead

https://doi.org/10.1016/S0140-6736(09)61460-4Get rights and content

Summary

If the pace of increase in life expectancy in developed countries over the past two centuries continues through the 21st century, most babies born since 2000 in France, Germany, Italy, the UK, the USA, Canada, Japan, and other countries with long life expectancies will celebrate their 100th birthdays. Although trends differ between countries, populations of nearly all such countries are ageing as a result of low fertility, low immigration, and long lives. A key question is: are increases in life expectancy accompanied by a concurrent postponement of functional limitations and disability? The answer is still open, but research suggests that ageing processes are modifiable and that people are living longer without severe disability. This finding, together with technological and medical development and redistribution of work, will be important for our chances to meet the challenges of ageing populations.

Introduction

The remarkable gain of about 30 years in life expectancy in western Europe, the USA, Canada, Australia, and New Zealand—and even larger gains in Japan and some western European countries, such as Spain and Italy—stands out as one of the most important accomplishments of the 20th century. According to the Human Mortality Database, death rates in life-expectancy leaders such as Japan, Spain, and Sweden imply that even if health conditions do not improve, three-quarters of babies will survive to celebrate their 75th birthdays. Most babies born since 2000 in countries with long-lived residents will celebrate their 100th birthdays if the present yearly growth in life expectancy continues through the 21st century (table 1). This forecast is based on the assumption that mortality before age 50 years will remain at 2006 levels. At age 50 years and older, probability of dying decreases by a rate that yields yearly improvements in period life expectancy of 0·2 years. More complex methods can be developed on the basis of the assumption that life expectancies will increase linearly;12 however, such models produce similar estimates to those given in table 1.

These scenarios are projections, but we do not have to look to the future for challenges of an ageing population: the oldest-old group (aged >85 years) have over past decades been the most rapidly expanding segment of the population in developed countries. This group is also the most susceptible to disease and disability.13, 14, 15, 16, 17, 18 Development of mortality, disease, and disability rates in elderly people will therefore have a fundamental effect on sustainability of modern society.

Section snippets

Mortality

Life expectancy is lengthening almost linearly in most developed countries, with no sign of deceleration. In 2002, Oeppen and Vaupel12 showed that best-practice life expectancy—ie, the highest value recorded in a national population—has risen by 3 months per year since 1840 (figure 1). Data for a further 7 years have since become available, and life expectancy keeps rising. In the record-holding country, Japan, female life expectancy was 86·0 years in 2007,19 surpassing the 85-year limit to

Health

Because health is a multidimensional notion, several indicators are needed to capture trends. On the basis of Verbrugge and Jette's34 framework, health deterioration can be described by risk factors that lead to diseases and conditions that can cause loss of function, and, dependent on the environmental context, can result in disability. To assess trends in health, investigators have to analyse trends in these different levels of health, bearing in mind that different indicators show different

Disease

The prevalence of diseases in the elderly population has generally increased over time. Most survey data are based on self-reported morbidity. Although self-reported data are often assumed to underestimate true prevalence, investigators36 report higher prevalences in a Dutch population of diabetes mellitus, cardiac disease, lower-back complaints, and asthma on the basis of self-reports than of medical records. However, increasing trends have generally been shown for both self-reports and

Functional limitations and disability

Improvements in mobility measured by single indices have been reported by many investigators in the USA.2 The yearly rate of improvement is typically around 1%. In Spain, between 1986 and 1999, improvements were reported on the basis of the Rosow-Breslau scale of items pertaining to stooping or kneeling, reaching or extending arms, pulling or pushing large objects, and handling or picking up of small objects.67, 68 A similar trend in the USA from the late 1970s to the late 1990s was reported in

Health expectancies

Health expectancies combine information about life expectancy and prevalence of good health, and thus directly address whether the period of morbidity or disability at the end of life is shortening or lengthening. Dependent on the measure of health, several health expectancies can be estimated:86 disease-free health expectancy, life expectancy in perceived good health, and disability-free life expectancy. Trends in these three measures differ. Life years with morbidity have been increasing in

Consequences of mortality, disease, and disability

Are we living not only longer, but also better? Most evidence for people aged younger than 85 years suggests postponement of limitations and disabilities, despite an increase in chronic diseases and conditions. This apparent contradiction is at least partly accounted for by early diagnosis, improved treatment, and amelioration of prevalent diseases so that they are less disabling.1, 6, 11, 99 An estimated 14–22% of the overall fall in disability can be attributed to reductions in disabilities

Search strategy and selection criteria

A series of reviews has dealt with population ageing and trends in health in the USA1, 2, 3, 4, 5, 6 and internationally.7, 8, 9, 10, 11 This Review builds on this work and includes new evidence available since 2004 from the International Network on Health Expectancies and Disability Process, the TRENDS network, and reports identified in PubMed and reference lists. We searched PubMed for reports published in 2005 and later using the search terms “active life expectancy”, “BMI/body mass index”,

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