System Ages: A Deeper Understanding of How You’ve Been Aging

Written and Reviewed by: Elysium Health

System Ages: A Deeper Understanding of How You’ve Been Aging

Key Takeaways:

  • Only 25% of how you age is determined by genetics. The rest is due to lifestyle and environmental factors.

  • Organs and systems age at different rates and some show greater variation between individuals than others. 

  • Biological age measures the age at which your body is expected to perform or function, providing insights into your overall health.

  • System ages represent the biological age of individual systems, such as the brain, heart, metabolic, and immune, and provide a snapshot of their relative contribution to your overall long-term health and wellness.

Related Products:

  • Index: A next-generation, DNA methylation-based biological age test. Measures 10 different aspects of aging, including nine system ages from a simple saliva sample.


Everyone ages at a different rate. Scientists estimate that genetics account for only 25% of this variation, with lifestyle and environmental factors providing a much greater influence. That’s great news: It means you can take control of how you’re aging, if only you can measure it. This is where biological age—and now, system age scores—comes in. 

Unlike chronological age, which tells you the number of years you’ve been alive, biological age measures the age at which your body is expected to perform or function, providing insights into your overall health. Biological age is determined by identifying epigenetic modifications across your genome that correlate with various aging outcomes. Epigenetics means “above” or “on top of” genetics. It refers to alterations that do not affect the sequence of the DNA, but have a significant impact on which genes are active. Our body is composed of different tissues and organs, and yet almost all the cells contain the exact same DNA sequence. Epigenetics is what makes a liver cell a liver cell and not a heart cell. They accomplish this by switching genes on or off that are relevant for each cell type. These “switches” can take different forms: DNA methylation, histone modification, and chromatin remodeling.

epigenetic regulation of gene expression

Epigenetic modifications also influence the aging process. And because epigenetic patterns across our genome change reliably with age-related comorbidities, epigenetic clocks like Index can be used to measure biological age. More importantly, these epigenetic modifications are reversible. They are influenced by lifestyle factors such as diet and exercise habits and other determinants like demographics. By monitoring your biological age over time with Index, you can determine how diet and other adjustments to your lifestyle impact your rate of aging.

Different Organs Age at Different Rates

Studies now suggest that, in addition to an overarching biological age, individual organs or physiological systems in our body have their own distinct biological ages. A study utilizing multiple types of data, including metabolomes, proteomes, blood chemicals, and phonemics, estimated that different organs (e.g., liver and kidney) or systems (e.g., immune and metabolic systems) age at different rates. Interestingly, certain organs and systems like the liver and hormone system were shown to exhibit greater variation between individuals than others. The brain, on the other hand, is considered one of the organs that ages faster.

It begins to decline in volume as early as your mid-30s. The rate of decline can vary, but by age 60, the brain typically has lost about 5% of its volume, and it accelerates from there. A meta-analysis investigating the presence of cell senescence markers in various human tissue samples demonstrated that the rate of senescence in the brain was significantly faster than in ten other organs examined (Tuttle et al., Aging Cell, 2019). The limited regenerative capacity of the brain tissue may be a contributing factor to its accelerated aging. Studies suggest that the hippocampus experiences a significant decline in “neurogenesis” potential—the ability to form new neurons—by middle age in humans.

A First-Ever Detailed View of Personal Aging

In 2023, Elysium introduced nine systems to Index in order to provide a higher-resolution view of your aging process. System ages represent the biological age of individual systems, such as the brain, heart, metabolic, and immune, and provide a snapshot of their relative contribution to your overall long-term health and wellness. Each system measure is based on DNA methylation signatures present in your genome that reflect a number of biomarkers relevant to that particular system. Biomarkers within each category were chosen for how closely they are associated with aging and overall long-term health and wellness. Elysium is pleased to be the first to offer this level of in-depth insight

What’s the relationship between system ages and overall biological age?

System ages are derived independently of biological age and of one another—so they won’t add up to your overall biological age. Instead, system ages offer a deeper insight into how each specific system has been aging. Your initial set of system ages can be thought of as your baseline profile. As you take additional tests, you can monitor how each system’s age changes over time and how it responds to lifestyle modifications you implement, such as altering your diet or exercise routine. 

It is also important to note that because research is beginning to suggest that different organs and systems age at different rates, comparing how your system has been aging relative to other individuals (e.g., your brain age compared to the population’s average brain age) can be more meaningful than comparing your systems to one another (e.g., your brain versus your heart). Index provides comparison charts that allow users to easily visualize how their biological age and system ages compare to others in the Index community. These charts are exclusive insights available to Index users who enroll in Elysium’s landmark longitudinal research study TIME-A (Translational Initiative to Map Epigenetics in Aging). 

TIME-A is a prospective aging study that aims to advance our understanding of the connections between epigenetics, lifestyle, demographics, and health and aging. While neither Elysium nor the broader research community has enough information at this point to fully comprehend the biology underpinning the differences in the aging rates of systems, Index is the only epigenetic age test to provide a systems-level view of personal aging for nine different systems. Understanding how different systems contribute to aging (and vice versa) is one of the many areas in the field of longevity that Elysium is working to advance. 

We encourage the Index community to enroll in TIME-A to collaborate with us in this effort. Participants will receive exclusive research updates and novel insights into how their rate of aging compares to the Index community while contributing to the advancement of aging research.

Can I Influence my system ages?

Unlike chronological age, biological age is not fixed or predetermined. Research suggests that your biological age can be influenced by environmental and lifestyle factors. The same is true of system ages, which represent the biological age of individual organs or physiological systems in your body. There are a number of lifestyle factors and changes that may influence the biological age of each system and have the potential to influence your score. For example, we recommend regular exercise for supporting a healthy brain because exercise has been shown to increase neurotrophic factors that regulate the growth and survival of neurons, affect brain plasticity, and influence cognition and well-being.

Index users receive over 100 science-backed recommendations that are likely to have the greatest impact on overall health and wellness and each system, based on the existing body of research. Please note that there is no guarantee that implementing these changes will improve your overall biological age or system age scores.

Why Precision Matters With Biological Age Tests

Like many other types of products, biological age clocks have varying degrees of reproducibility. Precision and reliability are especially challenging for measuring biological age at the individual level. A single sample processed repeatedly can result in epigenetic age estimates that vary up to nine years. That creates a lot of “noise” if you’re trying to measure your biological age—and the impact of lifestyle changes you implement—over time. 

To develop the most precise and reliable test, Elysium partnered with Morgan Levine, Ph.D., of Yale University—a leading epigenetics researcher. Index leverages a unique machine learning solution demonstrated in Nature Aging to be the most precise and reliable among published epigenetic age measures. 

How is this possible with a simple saliva test?

Unlike conventional biological age tests on the market that require a blood sample, Index uses a saliva sample to determine your overall biological age and the biological age of nine of your body systems. Saliva contains a mixture of cells and is a reliable, non-invasive source of high-quality genomic DNA that can provide insights into both your biological age and cumulative rate of aging. Elysium extracts DNA from the cells in your saliva sample for DNA methylation profiling. Unlike blood, saliva collection is non-invasive, convenient, and poses minimal discomfort or risk, unlike needle-based blood collection methods.

Looking Ahead to Future Measures

Elysium is engaged in multiple research projects with leading institutions to examine the various roles of epigenetics in aging. We expect to release additional measures and products related to epigenetics-based research in the near future. Subscribe to our newsletter to stay up to date on our latest research and offerings.

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