Here is a very accessible position paper from the Longevity Science Advisory Panel, a UK group interested in medical intervention in the aging process. You'll need to click through to download the full PDF version:
Understanding ageing is demanding. Within it is the paradox that all species, including humans, strive for survival but ageing and death are almost universal in the living world. In this paper we summarise a range of theories and mechanisms of ageing. There is little evidence that it is programmed into our genes and substantial evidence that it is malleable, in that lifespan has been lengthened by a variety of means in a variety of species. Just as important as the process itself is the fact that ageing is associated with an increased risk of many life-threatening diseases. If ageing can be delayed then it is likely that there will be a delay in the development of some or all of these diseases, leading to increased longevity.
Our goal for this project was to produce a report about the complex processes involved in ageing. We wanted it to be accessible to a wide spectrum of readers, not just those involved in academic study. We carried out an unusual research project which involved interviewing eight respected biogerontologists to identify current knowledge about the biology of ageing, which treatments may show promise in delaying the ageing process, and what they see as the future outcomes from scientific research on this topic. We supplemented these expert views with evidence from published studies on the effectiveness of the most promising new anti-ageing treatments, and developed a model to show what this might mean for the extension of human lifespan in the future.
From this research we have been able to build up a picture of the latest developments in this area. The experts tended to agree on which possible factors are important in understanding the biology of ageing. However, they did not necessarily agree on which are the most important components of the ageing process, or on which interventions might have the greatest potential for extending lifespan.