There has been some interest in deeper investigations of metabolism and aging in mammals via the study of hibernating species. For any stable altered state of metabolism, such as the calorie restriction response or hibernation, a greater understanding of the mechanisms involved may shed light on a range of issues. In the case of hibernation there is a long way to go yet, however. Research is still in the early stages, and comparatively few scientists study hibernation with this perspective:
The conventional wisdom in longevity research is that smaller species live shorter lives than larger ones. For example, humans and whales can live to be over 100; yet the average lab mouse doesn't live beyond its third birthday. The researchers found an exception to this pattern in a group of hamster-sized lemurs with a physiological quirk - they are able to put their bodies in standby mode.
Researchers combed through more than 50 years of medical records on hundreds of dwarf lemurs and three other lemur species for clues to their exceptional longevity. How long the animals live and how fast they age correlates with the amount of time they spend in a state of suspended animation known as torpor, the data show. Hibernating lemurs live up to ten years longer than their non-hibernating cousins. Dwarf lemurs were the most extreme examples in their study, spending up to half the year in deep hibernation in the wild. Dwarf lemurs go into a semi-hibernation state for three months or less in captivity, but even that seems to confer added longevity.
Hibernating dwarf lemurs can reduce their heart rate from 200 to eight beats per minute. Breathing slows, and the animals' internal thermostat shuts down. Instead of maintaining a steady body temperature, they warm up and cool down with the outside air. For most primates such vital statistics would be life-threatening, but for lemurs, they're a way to conserve energy during times of year when food and water are in short supply. Hibernating lemurs not only live longer, they also stay healthier. While non-hibernators are able to reproduce for roughly six years after they reach maturity, hibernators continue to have kids for up to 14 years after maturity, the researchers found. Although all species they examined suffered from cataracts and other age-related eye diseases as they got older, the hibernators managed to stave off symptoms until much later in life.