Random Thought: Declining Body Temp in old(er) adults

This New York Times (http://www.nytimes.com/2009/12/29/health/29real.html) article refers to a recent medical study that found that (apparently) the body temperature of older people declines with increasing age. The question of the relation between (I think oral) and real core temperature aside, the implication of the abstract of the article (http://www.ncbi.nlm.nih.gov/pubmed/18705705 itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum&ordinalpos=3) and and one for an older study (http://www.ncbi.nlm.nih.gov/pubmed/16398904?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_SingleItemSupl.Pubmed_Discovery_RA&linkpos=2&log$=relatedarticles&logdbfrom=pubmed)

is that a "fever" would be occurring at a lower temperature and hence a physician should consider any elevation of temperature as a possible indication of an infection or other inflammatory response.

This is most likely an important observation, but the interesting chemical engineering question that arises is what about the kinetics of the multitude of chemical reactions of life? If we assume Arrhenius kinetics with a nominal activation energy of (what else) 25kcal/mole, we could find that a reaction at 310C would be about 14 slower at 309C and 30% slower at 308C!

The question is if this difference matters to the health of the individual.

If one uses the logic that "evolution" is the ultimate optimization procedure, we would expect that all biological reactions have been optimized in terms of reaction pathways (energetically) and catalytic mechanisms -- with objective function apparently a combination of capital costs -- hardware necessary to run the process -- and operating costs (energy needed to run the reaction). If this is the case, then most processes could be "transport limited" that is the physical processes of diffusion (and convection) of chemical species and heat to and from the specific site of the reaction would limit how fast the reaction occurs. (We have made this argument in our research on transport processes in bone tissue.) If the reactions are transport limited, then the 1 or so degree C temperature change is not likely to matter.

However, most people older than about 30 will tell you that they don't recover from severe physical activity or injuries as fast as when they were younger. So something is changing with age.

Could it be the sustained temperature? Note that with injuries, there is usually significant inflammation which is associated with increased blood flow, so processes may occur at elevated temperatures that do not change with age. However, the question of recovery is interesting (as is the reason muscles hurt after lack of motion) (but I doubt that this is the complete answer: http://www.nytimes.com/2009/12/22/science/22qna.html?ref=science.)

It would be interesting to see if reduced chemical reaction rates because of lower temperature is part of the reason for various declines with age! Further, if there is a way to "warm" people to help them recover!