Global trends in life expectancy, at birth, at 30, and at 60, continue onward and upward at a fairly slow but steady pace: approximately two years every decade for life expectancy at birth and a year every decade for remaining life expectancy at 60. The research linked below crunches the numbers for the much of the world from 1990 to 2013, an extension of similar past studies to include more recent data. The authors show that lives are longer and age-related illness less severe, but the period of time spent in disability or illness has grown.
We are machines. Very complex machines, but nonetheless collections of matter subject to the same physical and statistical laws regarding component failure and damage as a car or an electronic device. Aging is damage, and a substantial portion of the trend in life extension is caused by an incidental, unintentional slowing of the pace at which that damage accrues. This slowing results from diverse causes, including control of infectious disease and reduction of the life-long burden imposed by infection, increased wealth and consequently greater access to medical care of all types, and an improved capacity to treat age-related medical conditions as they emerge. None of this is aimed at aging per se, and the historical trend in rising life expectancy has been slow precisely because there has been neither the ability nor the attempt to meaningfully intervene in the aging process.
What happens when you slow down the pace at which damage accumulates in a machine? You extend all the phases of its life span, both fully functional and in decline. At a given age its average level of dysfunction is lower than it would otherwise have been and it lasts longer as a result - but that also means it is spending more time with at least some dsyfunction before finally failing. The story should be little different for us, which is why I've long been fairly skeptical of the concept of compression of morbidity, wherein some factions of the research community suggest it should be possible to engineer a long period of good health followed by a rapid decline. In their defense, there are species, such as naked mole rats and salmon, that have exactly this shape to their lives, so it is clearly possible in principle. But in humans, with the way we work, intervention in aging means slowing down or repairing the damage, and slowing it down has this outcome of a longer period of a slower decline.
The future of health and longevity will look nothing like the past, however. The trend will not continue: it will leap to the upside in a much faster gain in longevity. This is because are now entering a transitional period in which researchers aim at the deliberate treatment of the mechanisms of aging, the underlying cause of age-related disease, rather than continuing expensive and ultimately futile efforts to patch over disease symptoms and proximate mechanisms. This is a night and day change in the entire approach to medicine, and upsets many regulatory frameworks and established business models, which means it has taken time and a lot of effort to get to the point at which enough people are on board to make it happen. We are close to the tipping point these days, but the vast majority of the money and the research community remains stuck in the past, working on strategies in medicine for age-related conditions that are now outmoded. Change is painfully slow in heavily regulated fields like medicine, and I expect that this transitional period will continue well past the point at which the first partial rejuvenation treatments are proven in the clinic, such as senescent cell clearance.
If we want to see the trends change, and the slowly lengthening period of slowly lessening disability be replaced by sudden leaps in life expectancy, accompanied by outright cures for many age-related conditions, then we have to make repair of the damage of aging a priority. Not merely slowing down the pace at which that damage accumulates as a side-effect of the operation of normal metabolism, but creating targeted biotechnologies capable of deliberate repair of the points of failure. More than enough is known today in order to do this, it is just a matter of finding the money and the will to proceed.
Global life expectancy has risen by more than six years since 1990 as healthy life expectancy grows; ischemic heart disease, lower respiratory infections, and stroke cause the most health loss around the world. People around the world are living longer, even in some of the poorest countries, but a complex mix of fatal and nonfatal ailments causes a tremendous amount of health loss, according to a new analysis of all major diseases and injuries in 188 countries. Global life expectancy at birth for both sexes rose by 6.2 years (from 65.3 in 1990 to 71.5 in 2013), while healthy life expectancy, or HALE, at birth rose by 5.4 years (from 56.9 in 1990 to 62.3 in 2013).
The study's researchers use DALYs, or disability-adjusted life years, to compare the health of different populations and health conditions across time. One DALY equals one lost year of healthy life and is measured by the sum of years of life lost to early death and years lived with disability. The leading global causes of health loss, as measured by DALYs, in 2013 were ischemic heart disease, lower respiratory infections, stroke, low back and neck pain, and road injuries. For communicable, maternal, neonatal, and nutritional disorders, global DALY numbers and age-standardized rates declined between 1990 and 2013. While the number of DALYs for non-communicable diseases have increased during this period, age-standardized rates have declined. The number of DALYs due to communicable, maternal, neonatal, and nutritional disorders has declined steadily, from 1.19 billion in 1990 to 769.3 million in 2013, while DALYs from non-communicable diseases have increased steadily, rising from 1.08 billion to 1.43 billion over the same period.
Global, regional, and national disability-adjusted life years (DALYs) for 306 diseases and injuries and healthy life expectancy (HALE) for 188 countries, 1990-2013: quantifying the epidemiological transition
The Global Burden of Disease Study 2013 (GBD 2013) aims to bring together all available epidemiological data using a coherent measurement framework, standardised estimation methods, and transparent data sources to enable comparisons of health loss over time and across causes, age-sex groups, and countries. The GBD can be used to generate summary measures such as disability-adjusted life-years (DALYs) and healthy life expectancy (HALE) that make possible comparative assessments of broad epidemiological patterns across countries and time. We used the published GBD 2013 data for age-specific mortality, years of life lost due to premature mortality (YLLs), and years lived with disability (YLDs) to calculate DALYs and HALE for 1990, 1995, 2000, 2005, 2010, and 2013 for 188 countries.
Sociodemographic status explained more than 50% of the variance between countries and over time for diarrhoea, lower respiratory infections, and other common infectious diseases; maternal disorders; neonatal disorders; nutritional deficiencies; other communicable, maternal, neonatal, and nutritional diseases; musculoskeletal disorders; and other non-communicable diseases. However, sociodemographic status explained less than 10% of the variance in DALY rates for cardiovascular diseases; chronic respiratory diseases; cirrhosis; diabetes, urogenital, blood, and endocrine diseases; unintentional injuries; and self-harm and interpersonal violence. Predictably, increased sociodemographic status was associated with a shift in burden from YLLs to YLDs, driven by declines in YLLs and increases in YLDs from musculoskeletal disorders, neurological disorders, and mental and substance use disorders. In most country-specific estimates, the increase in life expectancy was greater than that in HALE. Leading causes of DALYs are highly variable across countries.