Wednesday, February 11, 2009

Annual Review of Medicine Article on Life Extension

The latest issue of the Annual Review of Medicine has this excellent article on the prospects of life extension. This paper addresses many of the issues I have been pondering for the past few years. I would like to do a substantial post on these issues by am swamped at the moment. For now, here is a sample from the article:

The large increase in life expectancy observed during the last century was achieved without much increase in our understanding of the ultimate causes of aging and age-related diseases. Although lifestyle changes and the taming of age-related disease are likely to continue increasing human life span (see Figure 1), it remains an intriguing possibility that a major increase in life expectancy could be achieved through an understanding and manipulation of the basic principles governing the progressive loss of function and fitness that accompanies aging.

…. The age trajectory of mortality rates was initially thought to be exponential, with risk of death increasing progressively with age, but a decline in mortality at the extreme of age has been observed in medflies (4), as has a slowing in humans (5). There are several possible explanations for the slowing of mortality at older ages, including genetic factors; indeed, siblings of centenarians also enjoy significantly unusual longevity (6).

…. Human studies on interventions intended to extend life span or health span may stem from findings in laboratory animals or in humans. Several considerations relate to the potential human applicability of such an intervention, e.g.,
▪ Is it available, feasible, and safe for testing in humans?
▪ What would be its profile of positive and negative effects in people?
▪ At what age would it need to be started to be effective, and for how long would it need to be administered?
▪ If it needs to be started relatively early in life, would there be any differences in beneficial versus adverse effects at different stages of the life span?
▪ How would environmental factors affect its efficacy and safety?
▪ Would it be suitable for the general population or only for particular subgroups?
▪ Should it be administered systemically or only to certain tissues?

.... Over time, because of the compounding effects, small increases in average life expectancy can lead to very large increases in the size of a population. Some analyses suggest that improvements in health and longevity have resulted in enormous gains in economic welfare over the past century (81–83). Indeed, one estimate of the economic impact of post-1970 gains in life expectancy suggested that they might have added as much as $3.2 trillion annually to the U.S. economy, equal to 50% of GDP! These calculations depend heavily on the assumed economic value of a statistical year of life, but even if the gains were only a fraction of that amount, they would still be huge.

Great stuff!