A routine blood test might someday reveal more than just indicators of kidney disease, diabetes, or other health issues in older adults. It could also provide insights into whether an otherwise healthy individual today might be at higher risk of needing assistance with daily activities in the future.
Researchers at Keio University in Japan have identified two blood proteins that seem to predict the likelihood of disability in very elderly adults. These proteins are known as beta-2-microglobulin (B2M) and cystatin C.
This discovery comes at a time when societies worldwide are experiencing significant demographic shifts. Increasing longevity means more people are reaching their 80s and 90s, but aging doesn’t always equate to maintaining independence. In Japan, nearly 60% of adults aged 85 and older receive support through the national Long-Term Care Insurance system, highlighting the growing need for caregivers, healthcare services, and public resources.
Preventing disability is becoming just as critical as managing specific diseases. If healthcare providers can identify individuals at risk years in advance, they might implement strategies—such as strength training, nutritional improvements, or early treatment—to slow or prevent declines in physical function.
Associate Professor Yusuke Osawa and his team focused on adults aged 85 to 89 who were living independently. Their study involved 230 participants from the Kawasaki Aging Well-being Project, all of whom had no disabilities at the start. Instead of testing for just one suspected marker, the researchers examined 29 different proteins present in blood plasma. They then used machine learning and advanced statistical analyses to identify patterns linked to future disability and mortality.
Over approximately four and a half years, the study found that higher levels of B2M and cystatin C consistently predicted an increased risk of becoming disabled. Specifically, elevated B2M levels were associated with about a 35% higher chance of future disability, while higher cystatin C levels correlated with roughly a 42% increased risk. These associations remained significant even after controlling for other health factors and lifestyle variables.
While findings from a relatively small group aren’t enough to establish these proteins as definitive markers, the team validated their results using data from the Italian Invecchiare in Chianti (InCHIANTI) study, which tracks aging in a different population. In that group, higher levels of B2M and cystatin C also predicted greater likelihood of developing disability, especially among those aged 80 and older.
The consistency of these results across different populations—which differ in diet, environment, and healthcare—strengthens the case that these proteins could serve as reliable indicators. Both B2M and cystatin C are linked to kidney function, an area that naturally tends to decline with age. B2M is also associated with chronic low-grade inflammation, often called “inflammaging,” which has been connected to frailty and age-related illnesses.
One practical advantage of these proteins is that clinical tests to measure them already exist, making future application feasible. However, that doesn’t mean they should immediately influence medical decisions. More research is necessary to determine the specific levels that indicate increased risk, how these levels change over time, and whether testing adds meaningful information beyond current assessments.
The study also looked at potential blood markers related to mortality. Some candidates showed promise in the Japanese dataset but failed to replicate in Italy. This highlights the importance of validation before integrating new biomarkers into routine care.
Published by scientists from Keio University and the U.S. National Institute on Aging in the journal GeroScience, this research suggests that changes in kidney function and inflammation may signal the early stages of functional decline, well before disability becomes apparent.
While the study’s design—targeting initially healthy, very old adults and confirming results across different countries—is a major strength, larger studies will be essential to confirm these findings. It’s also important to remember that blood markers alone can’t explain all reasons why an older adult may lose independence, as factors like falls, arthritis, cognitive decline, stroke, social isolation, and nutrition also play crucial roles.
Ultimately, the most valuable future breakthrough will be whether identifying these markers can lead to effective interventions. Early exercise programs, nutritional support, or medical treatments might reduce the risk of decline if administered in time. If future research supports this, B2M and cystatin C could become part of a proactive approach to aging—helping doctors spot vulnerabilities early and work to preserve independence while there’s still time.