Evidence summary: Index (Elysium Health)

Index is Elysium Health's at-home saliva test [3]. You post a saliva sample to Elysium, and about six weeks after it arrives your results appear as pages in your online Elysium account [1][3]. Elysium lists a biological age, a "cumulative rate of aging", nine "system age" scores, lifestyle recommendations and an invitation to join its own research study [3]. Each new result needs a new kit [1].

A shortened sample report that Elysium sent us in October 2026 shows an overview page and one of the nine system pages. Elysium told us that the full report has a page for each system.

The laboratory extracts DNA from your saliva and measures DNA methylation, a chemical mark on DNA, across the genome on a custom chip that Elysium developed with Illumina [3]. That is the only laboratory measurement.

Everything else is calculated by Elysium's own model, which it runs on a platform it calls APEX [3]. Elysium says Index is based on a method published in 2022 for making epigenetic clocks more repeatable [4][7]. That paper describes the method and applies it to six public clocks, with open code; it does not name or describe Index [9]. A 2024 paper funded by Elysium says Index was "trained to predict" PhenoAge, an age score calculated from routine blood tests and designed to reflect the risk of death and disease [10]. The same paper calls Index "a new clock that has been commercialized by Elysium Health" and lists it separately from the "published DNAm‐based clocks" [10]. In the sources we reviewed, Index's training data, the sample type it was trained on, its formula and its accuracy are not published.

• Biological age: the model's main result [3].
• Cumulative rate of aging: your biological age divided by your calendar age [1][5]. Elysium told us in October 2026 that it is calculated this way. It is a lifetime average, not a current speed: for example (a made-up case), an estimate of 55 at age 50 gives 1.10.
• System ages: nine age scores for systems such as brain, heart, metabolic and immune, which Elysium says are "derived independently of biological age and of one another" [3][6]. Elysium says they "are not indicative of the health of a specific system" [4]. A sample report Elysium sent us also shows a "rate of aging" on a system page; its figures match that system's age divided by calendar age.
• Recommendations: lifestyle suggestions for each system [1]. Elysium says there is "no guarantee" that following them will improve your scores [6].

Saliva is not blood. Index's training target comes from blood tests, and the two published studies we found that computed Index used blood [10][11]. Elysium says Index is "optimized to deliver precise results from both blood and saliva" [8], but we found no published data on how it handles the difference. One study without vendor ties, which did not test Index, found "significant within‐person differences" between clock results from mouth and blood samples [13]. In another, also without vendor ties, a version of the PhenoAge clock built with the same 2022 method agreed only moderately between saliva and blood, and the authors say this level of agreement "may not be suitable in clinical or commercial applications that require absolute agreement between tissue types" [12].

Index is currently rated Insufficient on Compare [1]. The rating concerns the biological-age result Index gives from saliva, as a marker of age-related health. The cumulative rate of aging is worked out from that result, so the same limits apply to it. The rating does not cover the system ages, which in the sources we reviewed have no published validation. Nor does it cover the recommendations, disease risk or diagnosis, or the Index model's use in research on blood samples. This page explains that rating. It does not change it.

We rate Index Insufficient for its own biological-age result. In the sources we reviewed, no published study has examined the saliva result that customers receive: not its accuracy, its link to health, or how much it varies between tests.

• The model is not published. Elysium names a published method as the basis of Index [4][7], but that paper does not describe Index [9], and an Elysium-funded paper lists Index apart from the published clocks [10]. We found no paper that publishes the Index model itself.
• No saliva data. The two published studies we found that computed Index used blood [10][11]. Our methodology rates a commercial test "on the evidence for that product’s own output, not for the scientific method behind it" [2].
• No independent check. Both studies were funded or analysed in part by Elysium, and both had Elysium employees among the authors [10][11]. In the sources we reviewed, no researchers without Elysium ties have studied Index.
• No test of accuracy or outcomes. In the Elysium-funded 2024 study of older adults with mild memory and thinking problems, a higher Index ratio in blood went with a higher level of homocysteine, a substance measured in blood, at the same point in time; the correlation was modest (r = 0.23, where 1 would be a perfect match) [10]. In the sources we reviewed, no study has linked Index to later disease, physical function or survival.

The next tier up, Emerging, describes "pilot human studies" and evidence that "May be based on small sample sizes or vendor-only datasets" [2]. The two Elysium-linked blood studies could fit that description for the Index model used on blood, but not for the saliva result you buy. In the sources we reviewed, four of the criteria in our Insufficient tier fit: "Vendor-only claims without published validation", "Proprietary models without methodological transparency", "No independent replication or external validation" and "Marketing language exceeds published evidence" [2]. The second fits largely rather than fully, because the general method and the training target are disclosed. One of the tier's examples, "Clocks comparing across different tissue types without calibration" [2], is close to this case. Our confidence in Insufficient rather than Emerging is low to moderate. We are confident that the test does not reach Promising, which asks for a published method and "At least one independent replication or large-cohort validation" [2].

A peer-reviewed paper describing and validating the Index model in saliva, a study by researchers without Elysium ties, or published repeat-test data for the saliva test could change this rating.

• "Most precise". The product page says Index uses a solution "demonstrated in Nature Aging to be the most precise and reliable among published epigenetic age measures" [3]. That paper tested its method on six public clocks; it does not name, test or rank Index [9].
• "Within zero to 1.5 years". The science page says "Index shows agreement across replicates within zero to 1.5 years" [4]. The 2022 paper reports agreement within about 1.5 years for most repeat measurements of the same blood sample, for the public clocks it rebuilt, not for Index [9]. Re-measuring one sample also does not show how results vary between two samples taken on different days.
• Physical function. The product page says "Index is more predictive of physical functioning status than prior leading measures" [3]. It cites no study, and we found none that tested this for Index.
• "Pace of aging". The product page calls the cumulative rate of aging "the pace at which your body has been aging, also called your pace of aging" [3]. It is your biological age divided by your calendar age [1][5], an average over your whole life so far. We found no published study that validates it as a measure of how fast a person is aging.
• Tracking lifestyle changes. The product page promises a "Better ability to track lifestyle changes over time" [3]. In the sources we reviewed, there are no published repeat-test data for Index and no study showing that lifestyle changes alter Index results.
• First or only. The product page says "Elysium is the first to offer this level of insight" [3], and a system-ages blog calls Index "the only epigenetic age test to provide a systems-level view of personal aging for nine different systems" [6]. We cannot check this, and being first says nothing about accuracy. In the sources we reviewed, the system ages have no published validation.

In the sources we reviewed, no study has tested whether anything changes Index results from saliva. Two Elysium-linked studies measured Index in blood before and after a treatment:

• A 2024 re-analysis of a two-year trial of a vitamin treatment in 217 older adults with mild memory and thinking problems [10]. Across the whole group, neither the treated nor the placebo group's average Index ratio changed significantly [10]. The authors then focused on a subgroup with high homocysteine, chosen at the level where an earlier step of the same analysis had found a difference for Index, so their findings in that subgroup are exploratory [10].
• A 2024 randomised, placebo-controlled trial of a supplement in 40 people with COPD, a long-term lung disease, in which Index was measured in blood immune cells as an exploratory outcome [11]. Changes in Index did not differ from placebo [11].

Neither study used saliva, so neither shows whether the saliva test can detect change. This page is not a recommendation to take supplements.

In the sources we reviewed, there are no published data on how much Index results vary between repeat tests [1]. The 2022 method paper re-measured saliva from 8 people, all collected at one session, using the public clocks it rebuilt, not Index [9]. Its authors note that "Saliva may change in cell composition (epithelial cells vs. leukocytes) with repeated sampling" [9]. Elysium describes internal tests of saliva handling, such as a sample left on a desk for a week [4], but we found no published results.

Comparing the ratio between two tests does not show your rate of aging between them [1]. Because the ratio is a lifetime average, it moves even when the age estimate does not: in the made-up case above, an estimate that stays at 55 from age 50 to 51 takes the ratio from 1.10 to 1.08. Between tests a few months apart, the ratio moves almost entirely because the age estimate moved. Without repeat-test data, we cannot say how much of that movement is test variation. A sample report Elysium sent us describes a lower ratio at a later test as a decrease in your rate of aging. By the arithmetic above, a lower ratio shows only that the later age estimate was lower, relative to your calendar age, than the earlier one.

An Index result is one estimate from saliva, made by a proprietary model that an Elysium-funded paper describes as trained to predict a blood-test-based age score [10]. A result younger or older than your calendar age is a gap at one point in time. The ratio restates that gap as a lifetime average, not a current speed [1]. A lower result does not by itself mean better health. Elysium says the system ages do not show the health of a specific system [4]. Elysium also says Index is not a medical device and "is not intended to screen, diagnose, treat, cure, or prevent any disease or condition" [3]. The reviewed studies do not show whether using this test to guide decisions improves health.

Every published study we found that computed Index has ties to Elysium [10][11]. Elysium funded the 2024 vitamin analysis, and five of the paper's authors were Elysium employees with stock options [10]. Elysium also holds the exclusive rights to patents on the vitamin treatment the trial tested and sells it as a dietary supplement, and one co-author sits on Elysium's Scientific Advisory Board [10]. The COPD trial had other funders, but Elysium supplied the capsules and funded and carried out the methylation analyses, and two authors were Elysium employees who own shares [11].

Elysium did not fund the 2022 method paper, but it supplied the paper's paired blood and saliva repeat-measurement data [9]. Two of its authors built aging measures based on this technology, and Elysium licenses those measures through Yale University. One of the two had been a paid scientific advisor to Elysium, and another author had been an Elysium employee [9].

Elysium also sells supplements [3]. A sample report Elysium sent us lists supplements among ways to support the brain system. The individual recommendations were not included, so we do not know whether they name Elysium products.

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