Japan’s rapidly aging population is bringing a once-distant health challenge into sharp focus: how can doctors identify people who are likely to lose their independence before disability becomes obvious? A new study led by researchers at Keio University suggests that the answer may be partly visible in an ordinary blood sample. Two circulating proteins, beta-2-microglobulin (B2M) and cystatin C, were associated with a higher future risk of disability among community-dwelling adults aged 85 to 89. The findings, published in GeroScience, were also supported by data from an independent aging cohort in Italy, raising the possibility that routinely measurable blood biomarkers could help clinicians recognize vulnerability in the oldest-old earlier than traditional assessments alone.
The need for such predictive tools is particularly urgent in Japan, one of the world’s most rapidly aging societies. Nearly 60 percent of Japanese adults aged 85 and older already receive some form of support through the country’s Long-Term Care Insurance system. Yet disability often develops gradually, through a combination of declining muscle strength, reduced physical resilience, chronic disease, inflammation, and impaired organ function. By the time a person has difficulty walking, bathing, or managing daily activities, opportunities for prevention may already be limited. A reliable biological warning signal could allow healthcare professionals to intervene while older adults still retain enough physical capacity to benefit from exercise, nutritional counseling, rehabilitation, and other supportive measures.
The research team, led by Associate Professor Yusuke Osawa of Keio University’s Graduate School of Health Management, analyzed plasma samples from participants in the Kawasaki Aging Well-being Project, or KAWP. The discovery analysis included 230 adults who were free of disability when their blood was collected and who were followed for approximately 4.5 years. Rather than selecting biomarkers based only on pre-existing theories, the investigators used a data-driven screening strategy to examine 29 circulating proteins. Machine-learning methods and multivariable statistical models were then used to test whether protein concentrations were linked to the later development of disability or death.
Two proteins stood out consistently. Participants with higher levels of B2M and cystatin C were more likely to become disabled during follow-up. In statistical terms, each increase in B2M was associated with a hazard ratio of 1.35 for future disability, while the corresponding hazard ratio for cystatin C was 1.42. A hazard ratio above one indicates an elevated likelihood of experiencing the outcome over time, although it does not mean that every person with a high value will become disabled. Importantly, the associations remained after the researchers adjusted for age, sex, kidney function, lifestyle characteristics, and other potential confounding factors. This suggests that the proteins may capture aspects of biological vulnerability not fully reflected by conventional clinical measurements.
Cystatin C is a small protein produced by most nucleated cells and filtered from the blood by the kidneys. Because its concentration is less dependent on muscle mass than creatinine, the conventional marker used to estimate kidney function, cystatin C can be particularly informative in very old adults, whose muscle mass may be substantially reduced. B2M is also connected to kidney clearance, but it has an additional biological significance. It forms part of major histocompatibility complex class I molecules found on the surface of nearly all nucleated cells and can rise in conditions involving immune activation, inflammation, and altered filtration. In this sense, elevated B2M may reflect both impaired renal handling and persistent immune-system stimulation.
The researchers next asked whether the discovery could be reproduced outside Japan. They turned to the Invecchiare in Chianti, or InCHIANTI, study, a long-running investigation of aging in Italy that followed participants for as long as 15 years. In that independent population, higher concentrations of B2M and cystatin C were again associated with an increased risk of disability, particularly among adults aged 80 and older. Replication across geographically and culturally different cohorts is a crucial test for any proposed biomarker because it helps determine whether an association reflects a broadly shared biological process rather than a feature unique to one study population, healthcare system, or lifestyle pattern.
Not every signal from the Japanese analysis survived this external test. Epidermal growth factor and interferon gamma-induced protein 10 were initially associated with mortality, but their relationships were not consistently reproduced in the Italian cohort. The contrast strengthens the significance of the B2M and cystatin C findings: the two proteins were not merely part of a large list of statistically interesting molecules, but were among the markers showing the most durable connection with disability across populations. Still, the study is observational. It demonstrates association, not proof that raising or lowering either protein directly causes functional decline. The biomarkers may be indicators of several underlying processes rather than independent drivers of disability.
The biological picture emerging from the study is consistent with the concept of “inflammaging,” the gradual increase in low-grade immune activation that accompanies aging. Unlike an acute infection, inflammaging may persist quietly for years, contributing to vascular damage, muscle wasting, impaired repair, and reduced physiological reserve. Kidney dysfunction can add another layer of risk by allowing metabolic waste products and signaling molecules to accumulate in the circulation. In an 85-year-old, even modest changes in renal function or inflammatory activity may have consequences because the body’s ability to compensate for stress is already diminished. B2M and cystatin C could therefore act as accessible readouts of overlapping processes that precede visible disability.
“Our findings suggest that preserving healthy aging requires attention not only to diseases but also to the biological processes that precede disability,” Professor Yasumichi Arai of Keio University said. Earlier identification of high-risk individuals could create a window for interventions before decline becomes irreversible. Dr. Osawa noted that both proteins can already be measured using standard clinical assays, making them more practical than experimental markers that require specialized laboratory platforms. A future screening approach might combine B2M and cystatin C with information about gait speed, grip strength, nutrition, medication use, cognition, and social circumstances. Such a tool would not predict an individual’s fate, but could help direct limited preventive resources toward people most likely to benefit.
The study’s results point toward a shift in how healthcare systems think about longevity. Extending life without preserving mobility and self-sufficiency can leave older adults and families facing years of escalating care needs. Blood-based risk assessment could eventually support a more proactive model, in which clinicians monitor biological changes before a person requires long-term assistance. The next steps will include determining whether repeated measurements improve prediction, identifying clinically meaningful threshold values, and testing whether targeted interventions can alter outcomes in people with elevated B2M or cystatin C. For now, the findings offer a scientifically grounded lead: in the oldest-old, two familiar blood proteins may provide an early glimpse of the path toward disability—and a chance to change it.
Subject of Research: People
Article Title: Plasma proteins associated with disability and mortality risks in Japanese community-dwelling octogenarians
News Publication Date: 27-Jun-2026
Web References: https://doi.org/10.1007/s11357-026-02377-7; https://www.k-ris.keio.ac.jp/html/100007234_en.html
References: GeroScience. “Plasma proteins associated with disability and mortality risks in Japanese community-dwelling octogenarians.” DOI: 10.1007/s11357-026-02377-7.
Image Credits: Dr. Yusuke Osawa, Keio University, Japan
Keywords: aging, disability risk, biomarkers, beta-2-microglobulin, B2M, cystatin C, kidney function, inflammaging, healthy aging, long-term care, gerontology, blood proteins, preventive medicine, older adults, GeroScience
