This open access paper is an example of a model of future life expectancy that projects existing trends, with a little variation in here and there based on whether or not public health measures related to smoking and diet prove to be more successful or less successful. It predicts an average global increase in life expectancy of 4 to 5 years by 2040. In recent years I would have said that this is probably incorrect. I think we are at the point now in the development of rejuvenation therapies at which I can say that it is definitely incorrect. Any study that fails to consider progress in the treatment of aging as a medical condition is disconnected from reality.
Twenty years from now senolytic drugs will be used by a sizable percentage of the world's population, and will cost cents per dose. They will dramatically reduce the suffering and death resulting from inflammatory age-related diseases by removing some fraction of lingering senescent cells from old tissues. The first such therapies already exist today, are easily available, and some cost a few hundred dollars per dose or less. It isn't hard to see that the use of senolytics will spread like wildfire just as soon as the first clinical trials report their results over the course of 2019. Further consider that this is just one branch of rejuvenation biotechnology. Numerous other branches are under development today, and will certainly be clinically available by the late 2020s. The historical trend in life expectancy will be smashed; life expectancy will jump upward quite dramatically.
This was the first study to forecast a comprehensive set of cause-specific and all-cause mortality and associated indicators using a framework that allows for exploring different scenarios for many risk factors and other independent drivers. In our reference scenario, life expectancy was forecasted to continue increasing globally, and 116 of 195 countries and territories were projected to have significant advances in life expectancy by 2040. Gains were projected to be faster among many low-to-middle SDI countries, indicating that inequalities in life expectancy could narrow by 2040.
As shown by the better health scenarios, greater progress might be possible, yet for some drivers such as high body-mass index (BMI), their toll will rise in the absence of intervention. We forecasted global life expectancy to increase by 4.4 years for men and 4.4 years for women by 2040, but based on better and worse health scenarios, trajectories could range from a gain of 7.8 years to a non-significant loss of 0.4 years for men, and an increase of 7.2 years to essentially no change (0.1 years) for women.
In 2040, Japan, Singapore, Spain, and Switzerland had a forecasted life expectancy exceeding 85 years for both sexes, and 59 countries including China were projected to surpass a life expectancy of 80 years by 2040. At the same time, Central African Republic, Lesotho, Somalia, and Zimbabwe had projected life expectancies below 65 years in 2040, indicating global disparities in survival are likely to persist if current trends hold.
Taken together, our forecasts point to a world where most populations are living longer and many health improvements are likely to occur if current trajectories hold; at the same time, such gains are not without potential important social consequences, particularly if long-term planning and policy design are not fully considered today.
An important finding is that in the reference scenario, we forecasted slower progress in 2040 than that achieved in the past; however, in the better health scenario, global life expectancy improvements exceeded gains that occurred from 1990-2016. This forecasted slowdown in the reference scenario is rooted in a combination of several factors. First, some risks were projected to worsen in the future, most notably high BMI. Second, past progress on other leading risk factors for premature mortality, namely tobacco and ambient particulate matter air pollution, was highly variable and thus such heterogeneity was projected through 2040. Third, several countries that have already achieved higher levels of life expectancy have also had stagnated gains.