Why do cold-blooded species live longer in colder environments? Researchers have a prospective mechanism that is shared by mammals:
Scientists have known for nearly a century that cold-blooded animals, such as worms, flies and fish all live longer in cold environments, but have not known exactly why. Researchers [have] identified a genetic program that promotes longevity of roundworms in cold environments - and this genetic program also exists in warm-blooded animals, including humans. "This raises the intriguing possibility that exposure to cold air - or pharmacological stimulation of the cold-sensitive genetic program - may promote longevity in mammals."
Scientists had long assumed that animals live longer in cold environments because of a passive thermodynamic process, reasoning that low temperatures reduce the rate of chemical reactions and thereby slow the rate of aging. "But now, at least in roundworms, the extended lifespan observed at low temperature cannot be simply explained by a reduced rate of chemical reactions. It's, in fact, an active process that is regulated by genes."
[Researchers] found that cold air activates a receptor known as the TRPA1 channel, found in nerve and fat cells in nematodes, and TRPA1 then passes calcium into cells. The resulting chain of signaling ultimately reaches DAF-16/FOXO, a gene associated with longevity. Mutant worms that lacked TRPA1 had shorter life spans at lower temperatures.
Because the mechanisms [also] exist in a range of other organisms, including humans, the research suggests that a similar effect might be possible. The study also links calcium signaling to longevity for the first time and makes a novel connection between fat tissue and temperature response. Researchers have known that lowering the core body temperature of warm-blooded animals, such as mice, by 0.9 degrees Fahrenheit can extend lifespan by 20 percent, but it hasn't been practical for humans to attempt to lower the core body temperature.
It's worth noting that past research has shown that not all methods of lowering core body temperature in mammals will extend life. It matters how it's done, which suggests that it isn't so much temperature as the particular mechanisms that are running that is driving the effect. For example, calorie restriction is associated with a lower core body temperature.