One Blood Marker Linked to Thinking Skills and Longevity in People Over 100

A study of Japanese centenarians has identified a single blood marker that may predict both how well a person thinks and how long they live. Researchers found that a protein called neurofilament light chain (NfL) — which is released when nerve cells are damaged — was linked to lower scores on memory and thinking tests and a higher risk of death in people who have reached 100 years old.

This research adds to a growing body of evidence that a simple blood test could one day help doctors understand the health of the aging brain. For the general public, especially those with aging parents or grandparents, these findings offer new insight into what happens to the brain at the very limits of human life.

What the Study Found

The study, published in *JAMA Network Open*, looked at 495 Japanese centenarians with an average age of 104. Most participants were women. Researchers took blood samples and gave them cognitive tests, then followed them for up to 17 years.

Here are the key findings:

– Higher levels of NfL in the blood were linked to lower scores on the Mini-Mental State Examination (MMSE), a common test of thinking ability.
– Elevated NfL was also tied to a higher risk of death during the study period.
– A different marker, called amyloid-beta 42/40, was linked to worse thinking scores but not to mortality.
– Another Alzheimer’s-related marker, phosphorylated tau 181 (p-tau181), showed no significant link to survival.

The researchers noted that NfL seemed to be a more general marker of brain damage than the Alzheimer’s-specific markers. They wrote that NfL reflects “complex interactions between the nervous system and physiological systems such as immunity and vascular function.”

What Is Neurofilament Light Chain?

NfL is a structural protein found inside nerve cells. When these cells are injured or die, NfL leaks into the fluid around the brain and spinal cord, and then into the bloodstream.

Doctors already measure NfL in several conditions, including:

– Multiple sclerosis
– Amyotrophic lateral sclerosis (ALS)
– Traumatic brain injury
– Huntington’s disease
– Vascular brain injury

In general, higher levels of NfL in blood or spinal fluid signal that nerve damage is happening. This study suggests that even in extremely old people, NfL levels can reveal ongoing damage that affects both thinking and survival.

How This Compares to Earlier Research

The findings from Japan match what researchers have seen in other parts of the world. A separate study of Danish people in their 90s and 100s found that NfL was linked to mortality. The fact that the same pattern shows up in a completely different population — Japanese centenarians — makes the finding stronger.

Dr. Mathias Jucker, a researcher at the German Center for Neurodegenerative Diseases who was not part of the study, said he was pleased to see the results replicated. “This independent validation across distinct populations strongly supports the robustness of the findings,” he told MedPage Today.

He also noted that NfL may predict mortality in younger people, not just the very old. His team is now studying whether NfL works as a marker of aging in animals as well.

What the Numbers Mean

The study used several measures to assess the participants:

– MMSE scores range from 30 (normal) to 0 (severe impairment). The average score among participants was 13.7, which indicates significant cognitive decline.
– The Clinical Dementia Rating (CDR) scale goes from 0 (no impairment) to 3 (severe dementia). Among 436 people tested, 83 had a score of 0, 59 had a score of 0.5, and 129 had a score of 1.
– The average NfL level was 114.6 pg/mL, but values ranged widely — from 12.5 to 1,239.5 pg/mL.
– During follow-up, 466 participants (95.5%) died.

The researchers found that for every increase in NfL, the risk of death rose by 36% (hazard ratio 1.36). Higher NfL was also tied to lower MMSE scores after adjusting for other factors.

Why Alzheimer’s Markers Didn’t Predict Death

One surprising finding was that amyloid-beta and p-tau181 — proteins linked to Alzheimer’s disease — did not predict mortality in these centenarians. Only NfL did.

The researchers suggested that in people who live past 100, non-Alzheimer’s brain damage may matter more. They wrote that “nonamyloid-beta pathology or systemic pathology affecting neurodegeneration rather than amyloid-beta pathology itself may play a more significant role in the morbidity and mortality of centenarians.”

In other words, the brain damage that comes with extreme aging may be different from the damage seen in typical Alzheimer’s disease. Factors like chronic inflammation, poor nutrition, and declining kidney function — all reflected in NfL levels — may be more important at this age.

What This Means for You

For most people, reaching 100 is rare. But the study offers lessons for anyone concerned about brain health and aging:

– Blood tests for NfL are not yet routine, but they may become more common as research continues.
– The findings highlight that brain health is tied to overall body health — including immunity, blood vessels, and kidney function.
– Keeping your body healthy may help protect your brain, even at very advanced ages.

Practical Takeaways

While this study does not offer a direct action plan, experts generally agree on steps that support brain health throughout life:

– Control blood pressure and cholesterol to protect blood vessels in the brain.
– Stay physically active to reduce inflammation and support nerve cell health.
– Eat a balanced diet rich in fruits, vegetables, and healthy fats.
– Stay mentally and socially engaged to build cognitive reserve.
– Avoid smoking and limit alcohol use.

No single test can predict your future thinking ability or lifespan. But understanding markers like NfL helps researchers learn more about how the brain ages — and what might be done to slow that process.

Study Limitations

The researchers noted several limits to their work:

– They did not formally diagnose dementia in participants.
– They did not use brain imaging to look for other causes of damage, such as small strokes.
– The study only included Japanese people, so the results may not apply to other ethnic groups.

The authors called for replication in other populations to examine “potential cultural or genetic influences on NfL as a biomarker of aging.”

The Bottom Line

A single blood marker — neurofilament light chain — may offer clues about both thinking ability and survival in people who live past 100. While the study does not change current medical practice, it adds to our understanding of how the brain ages at the outer limits of human life. For now, the best strategy remains taking care of your overall health, which appears to protect both your body and your brain as you grow older.

Source: MedPage Today