More than half of babies born in rich nations today will live to 100 years if current life expectancy trends continue. And we are not only living longer than before, but those extra years are spent with less disability and fewer limitations on daily life than in the past. Furthermore, preliminary evidence suggests shortened working weeks over extended working lives might further extend increases in life expectancy and health. The issues are discussed in a Review in this week's Lancet, by Professor Kaare Christensen, Danish Ageing Research Centre, University of Southern Denmark, Denmark, and colleagues.
Huge increases in life expectancy (30 years+) have been seen in most developed countries over the 20th century. Death rates in nations with the longest life-expectancy (eg, Japan, Sweden, Spain) suggest that, even if health conditions do not improve, three-quarters of babies will live to see their 75th birthdays. But should life expectancy continue to improve at the same rate, most babies born in rich nations since 2000 can expect to live to 100 years. Thus, disease and disability rates in old age will have an increasing effect on the sustainability of modern society. The increases in life expectancy in rich countries evident since 1840 show no signs of slowing. The authors say: "The linear increase in record life expectancy for more than 165 years does not suggest a looming limit to human lifespan. If life expectancy were approaching a limit, some deceleration of progress would probably occur. Continued progress in the longest living populations suggests that we are not close to a limit, and further rise in life expectancy seems likely."
Mortality in people older than 80 years is still falling in rich nations. Data from more than 30 developed countries showed that in 1950 the probability of survival from age 80 years to 90 years was on average 15-16% for women and 12% for men. In 2002, these values were 37% and 25%. Since the death rates of children and young adults are very small in these nations, further increases in life expectancy will be achieved through further improvements in the oldest age groups. The authors use Germany as a case study, and show how in 2050, the German population will be substantially older and smaller than it is now. This prediction is typical of other developed nations too.
Total cancer incidence is rising due to more people living longer, and other chronic diseases such as diabetes and arthritis are also rising. Cardiovascular disease prevalence is also increasing-but this is thought to be because cardiovascular mortality is decreasing (so more people are alive with it since less are dying from it in any particular age group). Key to quality of life in old age is functional ability, and how it affects the activities of daily living (ADL). The activities of feeding, dressing, bathing or showering, transferring from bed and chair, and continence are central to self-care and are called basic ADL. Disability in instrumental ADL refers to disabilities affecting a broad range of activities, such as telephone use, shopping, doing laundry, housekeeping, preparation of food, using transport, handling drugs, and managing finances. Increasing evidence suggests that disability prevalence, as measured by these indicators, has been falling.
The European Health Expectancy Monitoring Unit is developing a common indicator of disability-free life expectancy named healthy life years (HLY). Time trends are available for 14 European countries between 1995 and 2003. People whose answers to the European Community Household Panel question "Are you hampered in your daily activities by any physical or mental health problem, illness or disability?" were "moderate" or "severe" are defined as disabled. On the basis of this measure, differences in HLY in European countries are large. Even among countries with similar yearly rates of increase in life expectancy, some countries show a rise (men: Austria, Belgium, Italy, Finland, Germany; women: Belgium, Italy, Sweden), others stagnation (men: France, Greece, Ireland, Spain; women: Austria, Denmark, UK, Finland, France, Spain, UK) or reduction (men: Denmark, Portugal, Netherlands, Sweden, UK; women: Germany, Greece, Ireland, Netherlands, Portugal) in the proportion of years spent disability-free at ages 65 years and older. Inequalities in HLY are even larger if all 25 countries of the EU are considered.
A series of studies has reported larger improvements in disability-free life expectancy than in life expectancy. A comparison of four health surveys in France concludes that gains in life expectancy over recent decades might have added years with moderate difficulties but not years with severe difficulties. This finding is backed by German and Belgian research. The authors say: "Continued improvement of health trajectories depends on improvement in elderly people, although the foundation for this progress might partly be based on enhanced living conditions and lifestyle early in life. Progress towards improvement of health is likely to depend on public health efforts to-for example, combat smoking, obesity, low levels of exercise, poor diets, and excess drinking, and to provide improved living conditions and care for elderly people with several ailments."
Are we living not only longer, but also better? Most evidence for people 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. People younger than 85 years are living longer and, on the whole, are able to manage their daily activities for longer than were previous cohorts.
For people aged older than 85 years, the situation is less clear. Data are sparse and widespread concern exists that exceptional longevity has grim results both for individuals and for societies. The authors discuss the "common view in clinical medicine and among some gerontologists that the substantial rise in proportion of exceptionally long-lived individuals in successive birth cohorts is the result of help given to an increasing proportion of frail and ill people into advanced old age, with huge personal and societal costs".
Danish research shows that the proportion of independent individuals is similar in those aged 100 to those aged 92-93 years; so while more people living longer puts a greater burden on society as a whole, exceptional longevity does not means exceptional levels of disability. But it is the overall financial burden of ageing populations that is causing most concern to developed nations. The old-age dependency ratio is the number of people aged over 65 years divided by those of working ages (15-64 years). In Germany, for every 100 people aged 15-64 years, the number aged 65 and over has gone from 16 in 1956 to 29 in 2006, and is expected to reach 60 by 2056.
The authors propose redistribution of employment as a possible strategy to cope with the economic implications of ageing. They say: "If people in their 60s and early 70s worked much more than they do nowadays, then most people could work fewer hours per week than is currently common-if they worked correspondingly more years of their longer lives. ...Preliminary evidence suggests that shortened working weeks over extended working lives might further contribute to increases in life expectancy and health. Redistribution of work will, however, not be sufficient to meet the coming challenges. Even if the health of individuals at any particular age improves, there could be an increased total burden if the number of individuals at that age rises sufficiently."
They conclude: "Increasing numbers of people at old and very old ages will pose major challenges for health-care systems. Present evidence, however, suggests that people are not only living longer than they did previously, but also they are living longer, with less disability and fewer functional limitations."
Professor Kaare Christensen, Danish Ageing Research Centre, University of Southern Denmark, Denmark. T) +45 6011 1886 E) firstname.lastname@example.org