Aging comes with the risk of some well-known physical changes. But one to keep an eye on — because it’s linked to serious complications such as frailty, falls and fractures — is sarcopenia. This is a gradual loss of muscle mass that actually begins around age 30. After that, you lose about 3 to 5 percent of your muscle per decade — although you might not really notice it until around age 60.
Muscle loss can eventually make it more challenging to do daily activities, such as walking, climbing stairs or carrying groceries. “When we think about aging and staying healthy and independent, skeletal muscle is absolutely essential … for quality of life and optimizing late-life function,” said Nathan K. LeBrasseur, director of the Robert and Arlene Kogod Center on Aging at the Mayo Clinic in Rochester, Minnesota.
But a recent study in MedScience found that sarcopenia has a surprising link to another health concern: infection risk.
In the study, researchers analyzed information from more than 458,000 adults ages 40 to 69 in the U.K. Biobank, a large database of volunteers’ medical information, making it one of the biggest studies on the relationship between muscle health and infection risk, said study co-author Jinbo Chen, in the Urology Department at Xiangya Hospital of Central South University in Changsha, China.
The participants were categorized as having no sarcopenia, pre-sarcopenia (just low muscle mass) or sarcopenia (low muscle mass and strength issues), using a number of assessments of muscle strength, lean body mass and physical performance.
Compared to people with no sarcopenia, both people with pre-sarcopenia and sarcopenia had higher risk of infections, including those of the urinary tract and skin. However, the relationship was strongest with respiratory infections and sepsis, a severe and often life-threatening immune response to infection or injury.
“Our results support the concept that skeletal muscle health is closely linked to immune resilience and infection susceptibility,” Chen said.
While it’s a large study with a long follow-up period, and the associations remained even when the researchers accounted for other factors such as age, socioeconomic status and other health concerns, it doesn’t yet tell us if low muscle mass actually causes more infections, if experiencing more infections causes low muscle mass, or if some other factor is responsible for both.
It’s not yet clear yet if there’s a true link, but the finding does make sense to LeBrasseur (who was also not part of the study), given muscle’s importance to overall health. “There’s this very interesting link of how much muscle we have and how we tolerate different stressors,” he said. People with more muscle mass tend to fare better when faced with the physical demands from surgery or chemotherapy, for example, he said.
He sees this resilience as potentially underlying a person’s response both to exercise and to infection. “When you exercise, you are actually stressing your system and challenging it to adapt to that stress,” LeBrasseur said. “Exercise is different than an infection, but you’re still challenging your molecular machinery and your cells to tolerate this stress, and then not just tolerate it but then respond and adapt to it,” he explained. This process may make the body better able to fight off infection, he said.
A subgroup analysis of younger study participants supported the importance of muscle mass rather than age alone: Younger adults with sarcopenia had an even higher risk of infection than older adults with sarcopenia in the study, which suggests that losing muscle prematurely could be a sign of underlying health concerns in younger adults, said David D. Church, assistant professor and director of the Center for Translational Research in Aging & Longevity at the University of Arkansas for Medical Sciences (UAMS) College of Medicine, who was not involved in the study.
The connection between muscle mass and immunity
This study builds on a growing body of evidence connecting muscle health and immune health. It’s not entirely clear yet what might explain this link, but there are several possible explanations.
First, people with sarcopenia often have other health concerns. They might be undernourished or frail, which makes it harder for their bodies to fight off infections. “Individuals with sarcopenia often have chronic low-grade inflammation, impaired immune responses, frailty and nutritional deficiencies, all of which may increase vulnerability to infections,” Chen said.
Inflammation seems especially important. In general, “muscle tissue loss is associated with systemic chronic inflammation and elevated pro-inflammatory markers, which further compromise the body’s ability to fight off infectious diseases,” Church said. Indeed, the researchers in the MedScience study found that certain inflammatory markers, identified via blood testing, partially explained the link they saw between reduced muscle mass and higher infection rates.
A limitation of the study is that sarcopenia was measured only once, which means it’s unclear how volunteers’ muscle mass changed over time and if that affected their infection risk. “Future studies with repeated measurements of muscle health will help clarify how changes in sarcopenia status influence infection risk over time.”
Additional research might also explore whether structured training programs could reduce infection risk, Church said, or if diet tweaks might help, Chen said.
In a 2022 systematic review, researchers found that regular resistance training over several weeks resulted in adaptations related to better immunity and reduced inflammation. (And even a single bout of strength training may increase activity among a number of different types of immune cells.) But whether that could translate to lower rates of infection is not clear.
How to protect yourself as you age
In the meantime, it’s never a bad idea to protect yourself from muscle loss (and potentially, infection) with regular exercise.
And you don’t have to do it a lot to benefit. The Center for Disease Control and Prevention’s guidelines for healthy adults recommend two full-body strength-training sessions per week. It takes time and dedication, but it’s worth it. “That’s a commitment to optimizing, preserving, improving your muscle health and function, and that’s critical,” LeBrasseur said.
It’s never too late to start, either. Research shows that people 75 and older who start strength training can still build muscle and improve day-to-day functioning.
Of course, maintaining muscle strength is just one component of an overall approach to healthy immunity and aging. You can, and should, also take steps to prevent infection as best as you can with “appropriate vaccination, good hygiene practices and management of underlying health conditions,” Chen said.
The post The surprising connection between age-related muscle loss and infection risk appeared first on Washington Post.
