Blood Test Predicts How Well You’re Aging in Real Time

Scientists have developed a new biological age test that measures how well you’re aging rather than just how old you are.

The IC Clock analyzes DNA patterns in blood or saliva to assess intrinsic capacity—the sum of six key functions including mobility, cognition, mental health, vision, hearing and vitality. Unlike existing aging clocks that focus on disease risk, this tool evaluates functional decline and could help doctors tailor treatments to preserve health rather than simply treat illness. The research, published in Nature Aging, represents a shift toward measuring what matters most to aging adults: maintaining independence and quality of life.

Function Over Disease Treatment

“Maintaining function during the aging process is what matters to older adults. Function should inform medical care instead of focusing on getting patients to some disease-free state,” said senior author David Furman, PhD, Buck associate professor and director of the Buck Bioinformatics and Data Science Core.

The World Health Organization recognized intrinsic capacity decline as a medical condition in 2022, adding it to the International Classification of Diseases. This official recognition validates what researchers have long suspected—that functional aging matters more than chronological age for predicting health outcomes.

The IC Clock emerges from this paradigm shift, offering a molecular-level assessment of how well someone’s body systems are maintaining themselves over time.

Superior Mortality Prediction

When tested against established aging clocks using data from the Framingham Heart Study, the IC Clock outperformed all previous generations in predicting overall mortality. The research revealed that people with high IC Clock scores live an average of 5.5 years longer than those with low scores.

This superior predictive power stems from the clock’s focus on functional capacity rather than disease markers. While other tests might detect cellular damage or inflammation, the IC Clock captures whether that damage translates into real-world limitations.

The tool showed particularly strong associations with death from cardiovascular disease, congestive heart failure, and stroke—conditions that significantly impact daily functioning before becoming fatal.

What the IC Clock Measures

The test evaluates six domains that determine healthy aging:

• Mobility: Physical movement and coordination abilities
• Cognition: Memory, thinking, and mental processing speed
• Mental health: Psychological well-being and mood stability
• Vision: Visual acuity and eye health
• Hearing: Auditory function and sound processing
• Nutrition/vitality: Energy levels and physiological reserve

Immune System Connections

One of the study’s most revealing findings involves the relationship between functional aging and immune system health. The IC Clock detected specific patterns in immune cell populations that predict how well someone is aging.

People with higher IC Clock scores showed increased expression of CD28, a protein essential for T cell activation that typically declines with age. They also had more naive CD8+ T cells and fewer exhausted immune cells, suggesting their immune systems retained youthful characteristics.

The research identified 578 genes whose expression correlated with IC Clock scores. Many of these genes regulate immune function, particularly T cell activation—confirming that immune system aging closely tracks overall functional decline.

Sex-Specific Aging Patterns

The research revealed intriguing differences in how men and women age across different functional domains. Men scored higher in psychological well-being and vitality, while women maintained better sensory function.

More surprisingly, the timing of decline varied by sex. Women experienced earlier sensory decline (around age 42) compared to men (age 67), while men showed cognitive decline earlier (age 72) versus women (age 86).

These patterns suggest that aging interventions might need to be tailored differently for men and women, targeting different systems at different life stages.

Diet and Lifestyle Factors

The study uncovered specific dietary patterns associated with better functional aging. People with higher IC Clock scores consumed more dark meat fish—including mackerel, salmon, and sardines—and had elevated blood levels of marine-origin omega-3 fatty acids.

Adherence to sugar intake guidelines also correlated with better IC Clock scores. Those who kept sugar consumption at or below 5% of total energy intake showed better functional aging than those who exceeded recommendations.

Interestingly, moderate beer consumption was associated with higher scores, though researchers caution this doesn’t necessarily prove causation and requires further investigation.

Molecular Mechanisms by Domain

Beyond overall intrinsic capacity, the researchers created domain-specific clocks that revealed how different aging hallmarks affect various functions. Higher vitality scores linked to mitochondrial electron transport chain activity, while better locomotion scores connected to cardiac muscle adaptation pathways.

Cognitive function showed an unexpected pattern—higher cognitive scores associated with lower expression of neuron development genes, suggesting that cognitive resilience might involve different mechanisms than simply maintaining more neurons.

Psychological well-being correlated with DNA repair pathways, indicating that genomic stability plays a crucial role in mental health during aging.

From Research Tool to Clinical Application

The IC Clock uses DNA methylation patterns—chemical modifications that don’t change DNA sequence but affect gene expression—from just 91 specific sites in the genome. This relatively small number makes the test practical for widespread use.

Furman’s team is developing a dried-blood spot version that would eliminate the need for clinic visits, making functional aging assessment accessible in low- and middle-income countries.

“If we can offer a scalable, affordable molecular level tool to assess functional decline, the IC Clock could help clinicians, researchers, and policy makers better identify at-risk individuals and tailor interventions that promote a longer healthier life,” he said.

Regulatory and Research Applications

The IC Clock addresses a significant regulatory challenge in aging research. While the World Health Organization recognizes intrinsic capacity decline as a medical condition, the FDA has yet to approve aging as a treatment target.

Furman thinks the IC Clock could provide a way to end the long-standing argument as to whether aging should be classified as a disease. “We hope the IC Clock will ultimately enable the FDA to approve treatments that would improve health and function in older adults.”

The tool is already being implemented in the XPRIZE Healthspan competition, where the Buck Institute team will use it to track responses to interventions designed to restore muscle, cognition, and immune function.

What Makes This Different?

Unlike previous aging clocks that focus on predicting chronological age or disease risk, the IC Clock directly measures functional capacity. This distinction matters because two people of the same chronological age can have vastly different abilities to live independently and enjoy life.

The clock can be calculated from either blood or saliva samples, with equivalent accuracy. This flexibility makes it suitable for research studies, clinical assessments, and potentially home testing scenarios.

Perhaps most importantly, the IC Clock provides a unified metric that healthcare providers can use to guide treatment decisions, moving beyond the traditional model of waiting for diseases to develop before intervening.

As populations worldwide age rapidly, tools like the IC Clock could transform how we approach aging—shifting focus from treating diseases after they develop to maintaining function and independence throughout the lifespan.