Metabolic Rate and Longevity
July 18 2008   |   Permanent Link
As an addendum to prior discussions of the plasma membrane theory of longevity and related metabolic rate correlations: "Metabolism is a defining feature of all living organisms, with the metabolic process resulting in the production of free radicals that can cause permanent damage to DNA and other molecules. Surprisingly, birds, bats and other organisms with high metabolic rates have some of the slowest rates of senescence begging the question whether species with high metabolic rates also have evolved mechanisms to cope with damage induced by metabolism. To test whether species with the highest metabolic rates also lived the longest I determined the relationship between relative longevity (maximum lifespan), after adjusting for annual adult survival rate, body mass and sampling effort, and mass-specific field metabolic rate (FMR) in 35 species of birds. There was a strongly positive relationship between relative longevity and FMR, consistent with the hypothesis. This conclusion was robust to statistical control for effects of potentially confounding variables such as age at first reproduction, latitude and migration distance, and similarity in phenotype among species because of common phylogenetic descent. Therefore, species of birds with high metabolic rates senesce more slowly than species with low metabolic rates."

Complicating Alzheimer's Disease
July 18 2008   |   Permanent Link
Researchers have demonstrated an Alzheimer's therapy that removes amyloid plaque, but that doesn't halt or reverse neurodegeneration: "The theory was that dementia could be slowed or reversed once the plaques were cleared, and experiments in animals have shown that removing these plaques improves brain function. ... long-term follow-up of Alzheimer's patients treated with [the therapy] did show, 'a reduction in the number of plaques in the brains of patients -- in some cases there was a virtually complete removal of plaques. Crucially, there was no evidence that the patients benefited by the removal of plaques and even those subjects with virtually complete removal continued to deteriorate and had severe end-stage dementia prior to their death.' ... [researchers now believe] that removing plaques - at least by this method - is unlikely to make a significant difference to the clinical outcome of patients with established Alzheimer's disease ... it strongly suggests that plaques are not sufficient on their own to account for disease progression."

On Predicting Longevity
July 17 2008   |   Permanent Link
For all the obvious reasons, actuaries would love to be able to predict human longevity with accuracy. But is that possible with present or near-future tools, even setting aside considerations of rapid progress in biotechnologies of rejuvenation? Researcher Leonid Gavrilov here excerpts some of a recent paper on that subject: "Who has a better chance to become a centenarian - a taller or a shorter person? Is it better to be slender or stout? We know that most centenarians are both short and slender in their body build, but these measurements made at older ages could be misleading because they might only reflect body shrinkage as a result of aging. We were also intrigued by other possible predictors of long life. Is it better to be a farmer or an actuary in order to survive to 100? Does the number of children a person has affect their chances to celebrate their 100th birthday? Is it better to have dark eyes or light eyes? All these personal characteristics could be useful for actuaries if a strong association between them and exceptional longevity were to be established."

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