Yes, Of Course it is the Case that Life Expectancy at Birth Grew More Slowly in the Second Half of the 20th Century
To my eyes, the researchers here hold a few somewhat strange views of historical life expectancy data and its meaning, mixed in with the sensible thoughts, not least of which is their expectation of a ceiling or maximum to life span to exist. A great transition in trends for life expectancy at birth took place somewhere in the midst of the 20th century. In the early decades of the century, medical science made enormous inroads in the control of infectious disease, and then through to the middle of the century implementations of those advances fell in cost and spread out to less wealthy regions of the world. Infectious disease kills people of all ages, and thus large gains in life expectancy at birth can be achieved by cutting down mortality, especially in childhood. By the latter half of the century, the more tractable problems related to infectious disease were dealt with and solutions implemented to at least some degree for much of the world's population. Subsequent gains in life expectancy then had to emerge from tackling age-related diseases or the other, harder remainder of infectious disease.
To date, age-related disease has proven itself to be far less tractable a problem. As Aubrey de Grey puts it, the research community essentially took the same high level strategies that succeeded in achieving control over most infectious disease and tried to apply them to age-related disease. That simply won't work - these are two very different situations with very different causes, and which require very different solutions. The result has been marginal, expensive treatments that take a long time to produce, and thus progress towards increased life expectancy at birth has slowed. Firstly, the paradigm must change, towards something more like the SENS vision for rejuvenation through repair of the cell and tissue damage that causes aging. Secondly, life expectancy at birth is not a good metric for assessing progress towards the control of aging. Something more like remaining life expectancy at 60 is the number to pay attention to.
Increases in human life expectancy have slowed dramatically across the world since 1950, according to a new study. Although a "ceiling effect" is expected as average lifespan approaches its biological limit, the study found that the trend towards slower gains - and even declines - in lifespan is worst among low-lifespan countries. "This is not about us hitting the ceiling; the slowdown has been sharpest in countries that have the most life expectancy to gain. It's a rebuke to the idea that you can fix global health just by inventing more stuff. New health technology has been essential to making strides in life expectancy, of course, but our predecessors in the 1950s were making faster progress with the basics of soap, sanitation and public health."
Researchers examined life expectancy data for 139 countries and for each one calculated the "decadal" life expectancy gain - the gain from a given year to a decade later - during the period 1950-2009. The analysis revealed that for the total sample, the mean decadal gain started at an impressive 9.7 years during the 1950s but fell more or less steadily to just 1.9 years during the 2000s. The study did not break down data by country or region. The researchers stratified the countries in the sample by their life expectancies, and found that the highest lifespan countries, with life expectancies at birth of at least 71 years, declined from a mean decadal gain of 4.8 years in the 1950s to 2.4 years in 2000-2010. That result was unsurprising, given that life expectancies in these countries are approaching the maximum lifespan of 71-83 years.
However, the researchers found an even steeper decline in countries in the lowest stratum of lifespan, with life expectancies under 51 years. For countries in this category the mean decadal change in life expectancy dropped continuously from a promising gain of 7.4 years in the 1950s to a worrisome loss of 6.8 years in the 2000s. In other words, the low-lifespan countries on average went from experiencing big gains to sharp declines in life expectancy. The HIV/AIDS pandemic, which generally hit hardest in low-lifespan countries, is a factor in this trend but doesn't fully explain it. "The slowdown in life expectancy gains started before AIDS hit in the 1980s and 90s and occurred even in regions that did not have big problems with this disease." He suspects that an important driver of the overall trend is a widespread failure of governance. "Nowadays, the countries with persistently low life expectancy are countries that generally are fragile states."