It is often noted that life expectancy roughly doubled during the 20th century, but that statistic is an unhelpful merger of two phases. Until World War II, gains in life expectancy were achieved mostly via a progressive lowering of mortality rates in infancy and childbirth; thereafter, the ages at which the most progress has been made are middle-age and above. Most demographers predict that these more recent gains, which have averaged roughly two years per decade, will continue for some time, at least so long as the current rise in obesity and its associated diseases is substantially curtailed by dietary, lifestyle and medical advances. This will have a dramatic impact on the world economy; the nature of that impact will depend heavily on choices we make concerning wealth distribution.
The success of postponing death from age-related causes has been something of a mixed blessing. The average age until which people remain relatively free of age-related ill-health has also risen, by an amount comparable to the rise in average longevity, but when specific age-related diseases are considered individually- the picture becomes mixed, with the average age of survival with cardiovascular disease diminishing but Alzheimer’s and cancer- rising.
The economic benefits of postponing age-related ill-health and death are also mixed. It has been estimated that progress against age-related disease has been good for the economies of the industrialised world over the past 50 years, due to an increase in the proportion of individuals who are net contributors to national wealth rather than consumers of it. However, because the age at which people retire has not remotely kept pace with rising life expectancy, the proportion of the population who are receiving pensions and related benefits has also risen, with the result that a major crisis of pension plans in both the private and public sector is looming. This problem is exacerbated in the short term by the “baby boom”, the sharp (albeit temporary) rise in the birth rate in the USA and elsewhere following World War II, which is just about to start feeding through into the pension system.
There are, therefore, considerable challenges facing the world’s major economies in regard to maintaining elderly people’s quality of life in the coming decades. How can these challenges best be addressed? Several options must be considered. Serveral considerations need to be taken into account.
Without a doubt, there will continue to be immense value in pursuing new ways to postpone the onset and progression of the major age-related diseases, especially those with a long survival time (such as Alzheimer’s disease). These diseases sharply diminish the quality of life of both sufferers and their loved ones, while the financial cost of caring for sufferers impacts the quality of life of the whole of society.
In principle, any economic benefit accruing from postponing age-related ill-health could be considerably increased if such therapies did not similarly postpone death. This concept, generally described using the term “compression of morbidity”, has been pursued by biogerontologists for the past 30 years. This argument brings its share of issues to consider. First of all, there is no evidence that therapies which put off health problems that come with old age but do not extend life by a comparable amount are feasible: it is intuitively much more likely that the period of ill-health will be shifted to an older age but not shortened. Secondly, it is not at all clear if the public wants a compression of morbidity: rather, there seems to be unequivocal support for interventions that keep the frail and sick elderly alive.
However, a robust reason for optimism about the impact of increasing life spans arises from the significant progress being seen in regenerative medicine, which is fast reaching a level of sophistication that will allow it to be applied to the immensely multi-faceted problem of ageing. Regenerative medicine has the crucial advantage that it actually reverses age-related decline, rather than merely retarding it. Thus bringing not just the obvious demographic impact, but an economic benefit as well.
To see this, we must consider the relationship between the average proportion of his or her life that an individual spends in poor health at the end of life and the proportion of people in that condition at any given instant. In a world where no progress is being made in postponing either age-related health problems or death, these proportions are clearly equal. But when progress is occurring, an asymptotic relationship emerges: there is a finite rate of progress in postponing aging beyond which no one is in a state of age-related ill-health. That rate is, of course, one year per year – only a few times what we are achieving already.
It is, however, crucial to bear in mind that preventative therapies exhibit a lag between their onset and their beneficial consequences. Accordingly, even if we were to develop therapies that postponed ageing that started in childhood, and we improved those therapies faster than one year of postponement per year, those unfortunates who are already too old to benefit from the therapies would remain in (or would enter) age-related ill-health just as they always have.
Thus, the ideal therapies, in terms of both quality of life and economic benefit, are regenerative interventions that benefit those who are already experiencing, or at least approaching, the decrepitude and disease of old age. Such interventions would reduce the number of such sufferers more rapidly than any other type of treatment, and the economic impact would be correspondingly more significant and rapid.
The sole question remaining, therefore, is: are such interventions feasible in the foreseeable future? In my view, they most certainly are. Regenerative medicine is arguably the most burgeoning field in the whole of biomedicine today, with progress on all fronts occurring by leaps and bounds. In large part, the foundations for applying it to ageing are already in place or imminent. What remains is to combine those therapies (which will inevitably be piecemeal) into a sufficiently comprehensive panel to span all the pathways by which lifelong accumulating molecular and cellular damage eventually causes age-related decline. Now is the time to really start addressing these challenges.
Aubrey de Grey is a biomedical gerontologist based in Cambridge, UK, and is the Chief Science Officer of SENS Foundation, a California-based 501(c)(3) charity dedicated to combating the aging process. He is also Editor-in-Chief of Rejuvenation Research, the world’s highest-impact peer-reviewed journal focused on intervention in aging. He received his BA and Ph.D. from the University of Cambridge in 1985 and 2000 respectively.
de Grey, A. (2007). Life Span Extension Research and Public Debate: Societal Considerations Studies in Ethics, Law, and Technology, 1 (1) DOI: 10.2202/1941-6008.1011
de Grey AD (2007). Alzheimer’s, atherosclerosis, and aggregates: a role for bacterial degradation. Nutrition reviews, 65 (12 Pt 2) PMID: 18240553