A number of research groups have spent the past few years aggressively mining the population of ongoing human longevity studies, taking advantage of the falling cost of biochemical and genetic assays in order to conduct as many tests as they can: the more data the better. This has resulted in a steady stream of papers that report an increasing number of correlations between specific biological markers and longevity in human populations - though as noted in past posts here, these rarely hold up in different study groups, indicating a large number of tiny contributions to longevity, most of which vary greatly in their effects between human lineages. Metabolism is ferociously complex, and the metabolic aspects that determine natural human longevity no less so.
At this point, there is more pouring of data into the hopper and sorting it all into buckets than there is real progress in understanding - that comes later. Here are two recent examples of this sort of research publication:
Cortisol levels are strongly associated with a person's health. Familial longevity and age assessment of facial photographs (perceived age) are both associated with morbidity and mortality. The present study aimed to investigate morning cortisol levels in familial longevity and the association of these levels with perceived age. ... Perceived age and serum morning cortisol levels were measured for 138 offspring from long-lived families and 138 partners from the Leiden Longevity Study. ... This study demonstrates that high levels of cortisol are associated with a higher perceived age. This association was attenuated in offspring from long-lived families compared to their partners, suggesting enhanced stress resistance in these subjects. Future research will be aimed at elucidating potential mechanisms underlying the observations in this study.
OBJECTIVES: To test whether lower serum uric acid (UA) levels are associated with longevity independent of renal function.
PARTICIPANTS: Long-lived individuals (LLI) of Ashkenazi Jewish ethnicity, their offspring and controls (without family history of longevity).
RESULTS: Offspring were less likely to have hyperuricemia and had lower UA levels than controls. ... Furthermore, significant association between UA levels in LLI and their offspring has been observed.
CONCLUSION: Offspring had lower UA levels than controls despite similar renal function, suggesting that other factors such as UA metabolism or renal tubular transport determine UA levels. The association between UA levels and longevity is particularly intriguing because UA levels are potentially modifiable with diet and drugs.
Interesting as these studies are - when you read through them in connection with the dozens of other correlation studies examining the biochemistry of human longevity - this is really all something of a sideshow. There is no such thing as useless knowledge in the long term, and this all goes towards the final complete understanding of human metabolism that will exist in the future, but it doesn't help us move any faster now towards the goals of engineered longevity. There is an existing, well-defined path towards the production of rejuvenation biotechnology, and that path is where the majority of funding and effort should go if we want to see a real impact on the future trajectory of our own longevity.