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Aging in bats is instructive


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Note that unlike most mammals, bats allow their body temperature to sink to the ambient temperature when they are not active, they essentially practice cold exposure all the time, and all winter long. As their temperature drops, they enter a torpor state, in which their metabolism slows down.

Relevant quote from Dean:



I too found this correlation between BAT and lifespan in small mammals pretty compelling. Here are the discussions about how brown fat plays into the longevity of these three extraordinary species - grey squirrels, bats, and naked mole rats. And the benefits of cold exposure and BAT not just isolated to these three long-lived species. This study [1] analyzed data from both controlled laboratory experiments and free-living populations of many species that spanned a wide range of latitudes, to see how longevity within-species correlated with climate. Here is what they did and what they found:


We compiled data for 30 species under laboratory conditions and for 67 free-living species (1,081 populations). These data represent 4 phyla and 23 orders from around the globe. The dataset contained representatives from terrestrial, freshwater, and marine environments, and of widely different average longevities [minimum average lifespan 11.6 d (Acartia tonsa), maximum 190.0 yrs (Margaritifera margaritifera)]. Latitude and lifespan were positively correlated in 85% of the species, although the relationship was statistically significant in only 39% of the cases. It is worth noting that under a null model without a latitudinal gradient in lifespan, the chances of obtaining 85% positive slopes are exceedingly small (χ2 = 27.597, P < 0.0001). Moreover, for all species with significant regressions, lifespan increased with latitude. As discussed below, it appears that much of this latitudinal variation may be explained by temperature using the MTE.


To summarize, in species that span a wide range of latitudes, the within-species longevity is pretty strongly correlated with how far north (or south, in the southern hemisphere) an individual lives. That is, cooler environments → increased lifespan across a huge range of land, freshwater and marine species. Although less compelling because it wasn't an interventional study, the wide range of species which exhibited a longer lifespan in cold climates is suggestive, particularly when linked with the evidence discussed here that people's HbA1c improves in winter months.


Overall, as you describe so well in your opening posts, the scientific evidence and our personal experience seem to show dramatic health and (potentially) longevity benefits may be possible as a result of cold exposure and other interventions to boost brown & beige adipose tissue. 





[1] Proc Natl Acad Sci U S A. 2009 Aug 18;106(33):13860-4. doi:
10.1073/pnas.0900300106. Epub 2009 Jul 30.
Latitudinal variation in lifespan within species is explained by the metabolic
theory of ecology.
Munch SB(1), Salinas S.
Many ectotherms exhibit striking latitudinal gradients in lifespan. However, it
is unclear whether lifespan gradients in distantly related taxa share a common
mechanistic explanation. We compiled data on geographic variation in lifespan in
ectotherms from around the globe to determine how much of this intraspecific
variation in lifespan may be explained by temperature using the simple
predictions of the metabolic theory of ecology. We found that the metabolic
theory accurately predicts how lifespan varies with temperature within species in
a wide range of ectotherms in both controlled laboratory experiments and
free-living populations. After removing the effect of temperature, only a small
fraction of species showed significant trends with latitude. There was, however,
considerable residual intraspecific variation indicating that other, more local
factors are likely to be important in determining lifespan within species. These
findings suggest that, given predicted increases in global temperature, lifespan
of ectotherms may be substantially shortened in the future.
PMCID: PMC2728985
PMID: 19666552


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