Aging is damage, and the body fails in the same way that any complex, damaged machine fails. If one slows the pace of damage accumulation, as technological progress over the past century has achieved to a modest degree, albeit by accident rather than intent, both overall life span and the time spent in a period of damage and dysfunction at the end of life should extend. This is what we see happening, as is noted by the authors of today's open access paper. In order to extend healthy life and put off that period of damage and dysfunction, periodic repair of the underlying damage of aging is required. You make a machine last longer in a useful way by maintaining it.
This approach of repair, targeting the cell and tissue damage that causes aging, was not attempted by the scientific and medical communities until quite recently. The first repair based rejuvenation therapies worthy of the name are the various senolytic treatments that selectively remove senescent cells from aged tissues. Lingering senescent cells actively disrupt tissue maintenance and function, and eliminating them has been shown to reverse aspects of aging in mice. Senolytics emerged in the past decade, and are only now entering human clinical trials as a means of turning back selected conditions in which they are known to be a major component of pathology. There is still a lot more of aging to address if we want to change the past trend of increasing life span coupled to a longer period of damage and decline.
Populations are ageing worldwide. Globally, the proportion of those aged 65 and over has increased by 9% in the last two decades, and is expected to grow by a further 16% by 2050. This demographic shift will require societies to adapt. If longer lives are spent in poor health, governments face the challenge of providing accessible, high quality and sustainable long-term care. The growth in life expectancy is a positive, but with this comes a responsibility to ensure people have the support they need as they age, and to facilitate ageing in place.
In 2019, the World Health Organisation (WHO) renewed its commitment to support countries to achieve longer and healthier lives with the Decade of Healthy Ageing 2020-2030 strategy. A critical part of achieving longevity is understanding whether longer lives are typified by more years spent in good health (compression of disability) or poor health (expansion of disability). This has important implications for the provision of health and care services to respond to the needs of people as they age. It is, therefore, crucial to keep abreast of trends, specifically how the growth in life expectancy is matched by a growth in years spent in good health.
Metrics to assess this most commonly include healthy life expectancy and disability-free life expectancy. Both provide an estimate of life expectancy spent in good health, but differ slightly with respect to their measurement. Healthy life expectancy tends to rely on single item questions of self-reported health, and is thus subject to fluctuations as expectations of health change over time. Disability-free life expectancy is often calculated from multiple items about activity limitations and/or dependencies, and therefore does not bear the same limitations as that of healthy life expectancy.
Previous reviews have summarised trends in total, healthy, and disability-free life expectancy, the most recently in 2016. Typically, such evidence shows that while people are living longer, gains in life expectancy are not consistently matched by a growth in the number of years lived in good health and free of disability. Nevertheless, this is an evolving evidence base requiring ongoing scrutiny.
This systematic review was undertaken to update our current understanding of trends in health expectancies in OECD high-income countries. The principal finding is that changes in health expectancies have not kept pace with the growth in life expectancy in a number of high-income countries. One clear exception was Sweden, where gains in women's disability-free life expectancy were greater than gains in life expectancy over a period of almost 20 years. In conclusion, a number of high-income countries, changes in health expectancies over time have not kept pace with the growth in life expectancy. That is, people are living longer but disability and poor health are occupying an increasing proportion of later life. Our findings suggest that countries still need to make significant progress to achieve the WHO's Decade of Healthy Ageing goal of healthier, longer lives for all.