Two common proteins found in blood may help doctors identify very old adults who are more likely to lose their independence in the years ahead.
The finding could eventually make it easier to offer exercise, nutrition or rehabilitation support before serious disability develops.
The research is especially important for countries such as Japan, where people are living longer and the population is aging rapidly. Reaching an advanced age is a major achievement, but staying able to walk, shop, dress and manage everyday life without help becomes increasingly difficult.
In Japan, nearly 60% of adults aged 85 and older already receive some support through the national Long-Term Care Insurance system. As the number of very old people grows, preventing or delaying disability has become an important goal for families and health systems.
Doctors already use blood tests to look for diseases such as diabetes, kidney problems and high cholesterol. However, there are fewer reliable blood markers that can tell doctors which apparently independent older people may be heading toward physical disability.
A research team led by Associate Professor Yusuke Osawa at Keio University investigated whether proteins circulating in the blood could provide such an early warning. The team also included Professor Yasumichi Arai of Keio University and Dr. Luigi Ferrucci of the U.S. National Institute on Aging.
The researchers first studied 230 adults between 85 and 89 years old who were living in the community and did not have a disability when the research began. The participants were part of the Kawasaki Aging Well-being Project in Japan.
Blood samples were examined for 29 different proteins. The researchers used computer-based methods and statistical analysis to search for proteins linked with disability or death during approximately four and a half years of follow-up.
Two proteins stood out: beta-2-microglobulin, usually shortened to B2M, and cystatin C. People with higher levels of either protein were more likely to develop disability later.
For B2M, each measured increase was associated with about a 35% higher risk of disability. For cystatin C, the increase in risk was about 42%.
Importantly, the relationship remained after researchers took other factors into account. These included age, sex, kidney function, lifestyle and other differences that could influence an older person’s health.
The researchers then asked whether the finding would appear in a completely different population. They turned to the InCHIANTI aging study in Italy, which has followed older adults for as long as 15 years.
The same two proteins again showed a connection with future disability. The relationship was particularly clear among people aged 80 and older, giving the researchers greater confidence that the Japanese findings were not simply a result of chance or a feature unique to one country.
B2M and cystatin C are interesting because both are connected with kidney function. The kidneys normally filter waste and many small molecules from the blood, and kidney performance often declines as people grow older.
B2M may provide information beyond kidney health. It has also been linked with long-lasting, low-level inflammation, a process that becomes more common with aging and is sometimes called inflammaging.
Scientists increasingly believe this persistent inflammation may contribute to weaker muscles, poorer physical function and several diseases of old age. B2M could therefore reflect several biological changes occurring as the body becomes more vulnerable.
Cystatin C is already commonly used as a blood marker for estimating kidney function. Because both proteins can be measured with existing laboratory tests, turning the findings into a practical clinical tool may be easier than if researchers had discovered rare or difficult-to-measure molecules.
The study was published online in the journal GeroScience. It provides evidence from both Japanese and Italian populations that B2M and cystatin C may help predict disability among adults who have reached very old age.
The findings are promising, but they do not mean that a single high blood test result can predict an individual person’s future. Disability is influenced by many factors, including existing diseases, muscle strength, nutrition, physical activity, falls, social circumstances and access to health care.
The study also examined proteins that initially appeared to predict death, but those findings were not confirmed in the Italian group. This makes the repeated results for B2M and cystatin C more noteworthy while also showing why independent testing is essential.
Overall, the research has an important strength: the main finding appeared in two separate populations from different countries. Still, larger studies are needed to determine useful cutoff levels and whether adding these blood tests actually improves predictions beyond ordinary medical assessments.
The biggest question is whether acting on this information can change outcomes. If future trials show that people with high B2M or cystatin C benefit from earlier exercise programs, nutritional support or rehabilitation, a simple blood test could eventually help older adults stay independent for longer.
Source: Keio University
