Scientists Figured Out Why We Feel Colder as We Age—and It’s Not What You Think

If you’ve ever lived with your grandparents or other seniors, you may have had some squabbles over the temperature setting being too low. That’s often because people feel more sensitive to the cold as they age. Research out this week appears to have figured out a key reason why this happens. Scientists at the City of Hope Medical Center in California studied brown fat cells in mice. They found evidence these cells are less able to switch into their highly active state in older mice. They also managed to reverse this sluggishness with a drug, suggesting it’s possible to safely restore people’s heat-burning potential. The findings offer a “fundamental understanding of the mechanisms underlying increased cold sensitivity in older individuals,” the researchers wrote in their paper, published Wednesday in the journal Nature. A less active furnace Humans and other mammals like mice carry three types of body fat: white, brown, and beige. White fat cells are primarily intended to store energy, while brown fat cells (also called thermogenic fat cells) play a key role in keeping our body temperature stable; beige fat cells can do both. There are several factors behind why people may feel colder as they get older, such as reduced blood flow to the extremities and a less responsive hypothalamus, the region of the brain that helps regulate body functions like sweating and shivering. But our body’s brown fat cells also seem to lose some of their punch over time. The team’s earlier work has shown that there are different types of brown fat cells, some of which are much better at generating heat. In this new study, the researchers used mice as a model to study the system that regulates the availability of these different types. They found that certain immune cells produce proteins that shift highly active brown fat cells into their sleepier state. Levels of these proteins typically decreased when the mice were exposed to cold and increased in the heat, thus allowing the body to react in real time to changing temperatures. In older mice, however, levels of these proteins tended to remain high, meaning the mice couldn’t generate heat from their brown fat cells as effectively as before. The researchers then used the drug mifepristone—best known for helping induce abortion in women—to suppress the activation of a pathway set in motion by the proteins, which prevented some of this age-related slowdown. What this could mean More work will obviously be needed to confirm whether this system operates the same in people as it does in mice. And the researchers aren’t saying that we can now easily reverse older people’s sensitivity to cold. Though mifepristone is safely used for abortion, it affects many different parts of the body, thus making it impractical as a treatment for rejuvenating brown fat cells, the researchers say. Assuming these findings do hold up, however, it’s possible that we could find other drugs or interventions that can safely boost the potency of brown fat cells. And such treatments could have all sorts of uses beyond reducing our heating bills. “Thermogenic fat also burns glucose and fat, and its activity tends to decline with age. If scientists can find a safe, precise way to restore that activity, this foundational research could eventually deepen our understanding of age-related metabolic problems, including obesity and type 2 diabetes,” said senior author Qiong “Annabel” Wang, an associate professor at City of Hope’s Arthur Riggs Diabetes & Metabolism Research Institute, in a statement from the institute. In the meantime, it’s perhaps nice to know that as I get older, I can just blame my orneriness about buildings being too damn cold on my aging biology.