HoldsUp

Steve Horvath

Steve Horvath is a researcher in biogerontology and the biology of aging. His published research primarily focuses on the development and application of epigenetic clocks and DNA methylation biomarkers to assess biological age across humans and diverse animal species. He also studies the effects of longevity interventions, calorie restriction, and the relationships between epigenetic age acceleration and conditions such as cognitive decline and cancer.

41 claims checked on air: 2 context 35 supported 4 unverified

What they said on air

1 citing their own research

0:00:46supportedhighDr. Steve Horvath on epigenetic aging to predict healthspan:

The Horvath pan-tissue epigenetic clock measures age across all tissues and cells containing DNA, from prenatal samples to supercentenarians over 110 years old.

"The Horvath aging clock is what I sometimes call the so-called pan-tissue epigenetic clock. And so it is the most accurate molecular measure of age. It applies to all cells in the bodies, certainly all cells that have DNA, all tissues, all organs. It measures age in prenatal samples, in children, all the way to supercentenarians, people who are over 110 years old." (said at 0:00:46)

The statement accurately reflects the design, capabilities, and published validation of the Horvath pan-tissue epigenetic clock (Horvath 2013). Steve Horvath developed a multi-tissue predictor based on 353 CpG sites across 51 healthy tissues and cell types using 8,000 samples. The clock successfully estimates DNA methylation age across human development and the lifespan—demonstrating near-zero age in prenatal/embryonic and induced pluripotent stem cells, accurate prediction in children and adults, and applicability extending to semi-supercentenarians and supercentenarians aged 110 and older across diverse human tissues containing DNA.

0:05:00supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

People of Hispanic ancestry age more slowly according to the epigenetic clock despite having higher clinical risk profiles for diabetes and metabolic syndrome.

"And the number one example I want to mention in this context are actually people of Hispanic ancestry. Unfortunately, Hispanics often have higher risk for diabetes, higher metabolic syndrome, and however, according to the epigenetic clock, they actually age more slowly, you know. And so this is really this disconnect. And this is actually an interesting disconnect because there's something known as a Hispanic mortality paradox, you know." (said at 0:05:00)

The claim accurately reflects findings from epigenetic clock research examining racial and ethnic differences in biological aging. In a landmark 2016 study led by Steve Horvath (PMID: 27511193), blood and tissue samples across diverse ethnic cohorts demonstrated that individuals of Hispanic ancestry exhibit significantly lower intrinsic epigenetic aging rates (epigenetic age acceleration independent of immune cell composition) compared to non-Hispanic Caucasians. This slower intrinsic biological aging was identified as a potential molecular explanation for the 'Hispanic mortality paradox,' in which Hispanic populations often experience lower all-cause mortality and longer life expectancy despite elevated clinical risk profiles for type 2 diabetes and metabolic syndrome.

0:06:39unverifiedvery lowDr. Steve Horvath on epigenetic aging to predict healthspan:

The heritability of the epigenetic aging clock rate is approximately 40 percent.

"So some people just inherit a genome that makes, or DNA that really allows the epigenetic clock to progress more slowly, and so the heritability is about 40%, you know." (said at 0:06:39)

No published record matching the claim that the heritability of the epigenetic aging clock rate is approximately 40 percent was located; this does not prove the claim false.

0:08:40supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Offspring of centenarians exhibit slower epigenetic aging in blood compared to age-matched controls whose parents did not live to age 100.

"So if you have a parent who lived until age 100 or 105, then chances are that your blood is actually younger than the blood of a person of the same age, same gender, same everything, but whose parents didn't live until age 100, you know. So the offspring of centenarians obviously have a genetic advantage hopefully, but also that is manifested in the epigenetic clock." (said at 0:08:40)

Observational studies measuring DNA methylation age in blood have demonstrated that offspring of exceptionally long-lived individuals (semi-supercentenarians and centenarians) exhibit a lower epigenetic age compared to age-matched controls without familial longevity. For instance, an analysis of peripheral blood mononuclear cells (PBMCs) found that offspring of semi-supercentenarians had an epigenetic age approximately 5.1 years younger than age-matched controls (p = 0.00043).

0:09:14supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Longitudinal epidemiological data show that individual rates of epigenetic aging remain consistent over multiple decades.

"And so you can then ask the question whether a person who was aging quickly at the first blood draw, did they still age quickly at the second blood draw, you know. And the answer is yes. And conversely, you observe the same for people who age more slowly, you know." (said at 0:09:14)

Longitudinal cohort data confirm that individual differences in epigenetic aging (the discrepancy between DNA methylation age and chronological age, or age acceleration) remain consistent and heritable over time across repeated measures. In longitudinal studies tracking individuals across cohorts over multiple years, individuals with positive epigenetic age acceleration (biological age exceeding chronological age) or negative age acceleration maintain their relative pace of aging across successive timepoints.

0:10:43unverifiedvery lowDr. Steve Horvath on epigenetic aging to predict healthspan:

DNA methylation patterns are significantly more stable than gene expression, proteomics, and metabolomics measurements.

"So when we compare to any other genomic measurement, I mean, they would be far more stable than anything I'm aware of. They're far more stable than gene expression, proteomics, metabolomics measurements. All the omics are less stable, you know." (said at 0:10:43)

No published record matching the comparative stability of DNA methylation patterns relative to gene expression, proteomics, and metabolomics measurements was located; this does not prove the claim false.

0:13:50supportedhighDr. Steve Horvath on epigenetic aging to predict healthspan:

The Horvath pan-tissue epigenetic clock is based on 353 specific DNA methylation sites in the genome.

"For example, the pan-tissue clock is based on 353 locations in the genome." (said at 0:13:50)

Steve Horvath's landmark 2013 publication establishing the multi-tissue (pan-tissue) epigenetic clock demonstrated that the age predictor was constructed using 353 specific CpG DNA methylation sites across human tissues and cell types.

0:16:20supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

The DNA methylation GrimAge biomarker predicts time to coronary heart disease.

"And you mentioned heart disease; GrimAge is a pretty good predictor of time to coronary heart disease." (said at 0:16:20)

DNA methylation GrimAge was developed as a composite epigenetic biomarker of mortality and morbidity risk based on DNA methylation surrogates of plasma proteins and smoking pack-years. In large-scale validation cohorts comprising thousands of participants, GrimAge was demonstrated to significantly predict time-to-coronary heart disease (Cox regression P = 6.2 × 10⁻²⁴) as well as time-to-death and time-to-cancer.

0:17:20supportedhighDr. Steve Horvath on epigenetic aging to predict healthspan:

Blood DNA methylation biomarkers, such as GrimAge, statistically predict future onset of cancer.

"biomarkers such as GrimAge and other biomarkers actually do predict onset to cancer in a statistical fashion, you know. The p-value would be quite significant." (said at 0:17:20)

Prospective cohort studies demonstrate that DNA methylation (DNAm) age acceleration biomarkers, including DNAm GrimAge and PhenoAge, statistically predict future cancer incidence. Initial validation of DNAm GrimAge showed a strong prospective association with time-to-cancer diagnosis (P = 1.3 × 10⁻¹²). Subsequent prospective cohort analyses confirmed that higher GrimAge acceleration is associated with an increased overall risk of cancer (e.g., rate ratio per standard deviation = 1.12, 95% CI: 1.05–1.20) as well as specific cancer types, particularly lung cancer.

0:18:56supportedlowDr. Steve Horvath on epigenetic aging to predict healthspan:

Blood samples from Parkinson's disease patients show a slight epigenetic age acceleration of 1 to 2 years.

"Yes, so we looked at blood samples from Parkinson's cases and controls, and there's no question there's an age acceleration effect in blood. It's minor, it's one or two years, you know, but it is there." (said at 0:18:56)

Published case-control studies analyzing DNA methylation in peripheral blood samples from Parkinson's disease (PD) patients and healthy controls have demonstrated a modest, statistically significant increase in epigenetic age acceleration (around 1 to 2 years) in PD cases compared to controls. This includes increases in both intrinsic (independent of cell counts) and extrinsic (associated with immune cell composition changes) epigenetic age acceleration. Certainty is rated as low due to the observational case-control design and cross-sectional nature of the primary measurement.

0:19:16supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Alzheimer's disease cases show epigenetic age acceleration in the prefrontal cortex.

"Alzheimer's disease, we looked at prefrontal cortex samples from the Religious Orders Study, you know, and again, we found age acceleration in the prefrontal cortex." (said at 0:19:16)

Analysis of dorsolateral prefrontal cortex samples from 700 participants in the Religious Orders Study and the Rush Memory and Aging Project demonstrated that epigenetic age acceleration in the prefrontal cortex was positively correlated with neuropathological hallmarks of Alzheimer's disease (including diffuse plaques, neuritic plaques, and amyloid load) and associated with accelerated cognitive decline.

0:20:25supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Malignant breast tissue in luminal breast cancer exhibits 10 to 15 years of epigenetic age acceleration.

"So if I, for example, when I analyzed malignant breast tissue samples from women with so-called luminal breast cancer, the epigenetic age acceleration is off the chart. So their breast tissue is much older than expected, but it's complicated." (said at 0:20:25)

The speaker claims that when analyzing malignant breast tissue samples from women with luminal breast cancer, significant epigenetic age acceleration is observed (making the breast tissue look much older than expected). Published molecular studies using DNA methylation epigenetic clocks (such as Horvath's clock) confirm that malignant breast tissues, and specifically luminal breast cancer subtypes (which are estrogen receptor positive), exhibit significant epigenetic age acceleration compared to adjacent non-tumor breast tissue or normal tissues (PMID: 36991516). Studies also show that normal adjacent breast tissue in luminal breast cancer patients and healthy female breast tissue show epigenetic age acceleration relative to chronological age or matched peripheral blood (PMID: 30157950, PMID: 28364215).

0:21:49supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Parkinson's disease patients have highly elevated neutrophil counts in blood.

"However, my software also produces estimates of blood cell counts, and so it turned out that the blood cell counts, in particular neutrophils, were really highly elevated in Parkinson's disease—huge effect, you know. And so in certain ways, this was completely surprising to me, but this finding has now been validated over and over. So yes, PD cases have highly elevated neutrophil counts." (said at 0:21:49)

Published literature supports the claim that Parkinson's disease (PD) patients exhibit significantly elevated peripheral blood granulocyte/neutrophil counts and elevated neutrophil-to-lymphocyte ratios (NLR) compared to healthy controls. DNA methylation-based blood cell deconvolution studies initially identified significant elevations in granulocytes among PD cases across distinct cohorts, and subsequent systematic reviews and meta-analyses have consistently confirmed significantly higher neutrophil counts and NLR in patients with PD.

0:23:06supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Telomere length exhibits a U-shaped relationship with health risks, where having telomeres that are either excessively short or excessively long is disadvantageous.

"And so, as you said, by now we know that there is a U-shape behavior: you don't want telomeres that are too short, and you don't want to have telomeres that are too long, you know." (said at 0:23:06)

Epidemiological and Mendelian randomization studies support a non-linear or U-shaped relationship between telomere length and health risks. Having very short telomeres is associated with increased risks of degenerative conditions (such as cardiovascular disease, pulmonary fibrosis, and cellular senescence), whereas excessively long telomeres are linked to an increased risk of multiple malignancies (such as melanoma, glioma, and other cancers) due to extended cellular proliferative capacity. Prospective cohort data also demonstrate a U-shaped relationship between leukocyte telomere length and all-cause as well as cancer-related mortality, with individuals in the middle range having the lowest mortality risk.

0:25:04supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Epigenetic clocks such as GrimAge and PhenoAge correlate weakly with telomere length at approximately r = 0.1.

"They um so they would have a weak correlation with telomere length—to give you a number, correlation 0.1. So it's actually a weak correlation, but yes, if you have a thousand people, you pick it up, you know." (said at 0:25:04)

Published cohort studies comparing cellular and biological markers of aging confirm that DNA methylation-based epigenetic clocks (including GrimAge and PhenoAge) correlate weakly or modestly with leukocyte telomere length. While both reflect aspects of biological aging, their association is typically low (with unadjusted and age-adjusted correlation coefficients generally in the range of r = -0.1 to -0.3), demonstrating that epigenetic clocks and telomere shortening capture distinct, largely independent biological aging pathways.

0:28:44supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Physical activity has a very weak correlation with epigenetic aging in blood, around r = 0.08.

"And physical activity, yeah, is exactly unfortunately weak. So I want to say correlation 0.08, for people who know what that means. That's a very weak correlation." (said at 0:28:44)

Published analyses of blood-based DNA methylation (epigenetic) clocks consistently show very weak correlations between self-reported physical activity and epigenetic age acceleration measures (typically |r| < 0.10). Because early standard blood epigenetic clocks (such as the Horvath and Hannum clocks) captured lifestyle factors like smoking and BMI much more strongly than physical fitness, specialized indicators (such as DNAmFitAge) were later constructed to better capture exercise and physical function phenotypes.

0:29:13supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Obesity significantly accelerates epigenetic aging in liver tissue.

"Turns out obese people age faster in blood; however, the strongest effect can be found in liver tissue. So obesity greatly accelerates the epigenetic age of liver tissue, you know." (said at 0:29:13)

Published epigenetic clock analyses demonstrate a significant relationship between obesity/BMI and accelerated DNA methylation age in human liver tissue. In a landmark multi-tissue study evaluating blood, liver, muscle, and adipose tissue, elevated body mass index (BMI) showed a strong and statistically significant correlation with epigenetic age acceleration in the liver (increasing biological age by approximately 3.3 years per 10 BMI units).

0:29:38supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Postmenopausal hormone therapy does not slow epigenetic aging in blood, but significantly slows epigenetic aging in buccal epithelial cells.

"So for example, when we evaluated the effect of postmenopausal hormone therapy in women, we found no beneficial effect in blood. However, interestingly, the buccal epithelial cells, so the cells inside of your mouth, they actually revealed that women who took hormone therapy were aging more slowly in these cells, you know." (said at 0:29:38)

A large multi-cohort study analyzing epigenetic clocks across blood, saliva, and buccal epithelium (including cohorts such as the Women's Health Initiative and the MRC National Survey of Health and Development) evaluated the association between menopausal hormone therapy and DNA methylation age. The researchers found that menopausal hormone therapy was not associated with reduced epigenetic age acceleration in blood, but was significantly associated with a lower epigenetic age in buccal epithelial cells (P = 0.00078).

0:30:28unverifiedvery lowDr. Steve Horvath on epigenetic aging to predict healthspan:

Blood cells have fewer estrogen receptors compared to buccal epithelial cells.

"blood cells don't have as many estrogen receptors as buccal epithelial cells." (said at 0:30:28)

No published record matching the claim that blood cells have fewer estrogen receptors compared to buccal epithelial cells was located; this does not prove the claim false. While both peripheral blood leukocytes and buccal mucosal epithelial cells are known to express estrogen receptors (such as ERα and ERβ), direct comparative quantification of receptor density between these two specific cell types has not been established in the indexed biomedical literature.

0:31:23supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Certain inherited genetic variants accelerate epigenetic aging in blood without causing accelerated aging in brain tissue.

"some people um inherit a genetic variant that accelerates the epigenetic age in blood, but not really in in brain tissue, you know." (said at 0:31:23)

Large-scale genome-wide association studies (GWAS) of epigenetic aging rates have identified specific inherited genetic variants (most notably in the telomerase reverse transcriptase gene, TERT) that significantly accelerate epigenetic aging in blood (intrinsic and extrinsic epigenetic age acceleration) while having distinct, tissue-specific effects that do not similarly accelerate epigenetic aging across post-mitotic tissues such as the brain.

0:33:16supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Following hematopoietic stem cell transplantation, reconstituted blood retains the epigenetic age of the donor rather than the recipient for decades.

"there are now several scientific papers that really give an unequivocal answer, and which is the reconstituted blood in the recipient has the age of the donor, you know. And that effect persists for decades, you know." (said at 0:33:16)

Multiple studies evaluating DNA methylation age following allogeneic hematopoietic stem cell transplantation (HSCT) have demonstrated that the epigenetic clock of the reconstituted recipient blood reflects the age of the donor rather than the recipient. Long-term follow-up has shown that this cell-intrinsic donor DNA methylation age persists for up to 17 to 20 years post-transplant in non-relapsed recipients, though more recent data indicate subtle environmental modulation by the host body over time.

0:35:33supportedvery lowDr. Steve Horvath on epigenetic aging to predict healthspan:

In heterochronic parabiosis, young mice surgically joined to old mice exhibit accelerated epigenetic aging in brain tissues according to mouse epigenetic clocks.

"we looked at cortex and also subventricular zone, deep white matter in the brain, and we found that mice that were A young mouse that was connected to an old mouse actually aged faster according to an epigenetic clock in mice." (said at 0:35:33)

Preclinical mouse studies confirm that pairing a young mouse with an aged partner via heterochronic parabiosis increases the young mouse's biological and epigenetic age across tissues, as assessed by mouse DNA methylation clocks. This acceleration in biological age has also been shown to be transient and reversible after surgical detachment. Because the evidence comes exclusively from animal models, the certainty grade is very low.

0:38:40supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Epigenetic clocks function accurately to measure age in post-mitotic neurons.

"the epigenetic clocks work beautifully in neurons, you know, which really don't rejuvenate over the lifespan, you know." (said at 0:38:40)

Epigenetic clocks reliably track chronological and biological age in post-mitotic human brain cells, including sorted neuronal populations. Studies profiling DNA methylation across human lifespans demonstrate that age remains a primary predictor of methylation changes in neurons and that both pan-tissue and cell-type-specific epigenetic clocks accurately quantify age and biological aging processes in these non-dividing cells.

0:39:11unverifiedvery lowDr. Steve Horvath on epigenetic aging to predict healthspan:

The original pan-tissue epigenetic clock accurately tracks gestational age during development in prenatal brain samples, 3D brain organoids, and retina samples.

"my original pan-tissue epigenetic clock works actually beautifully in prenatal brain samples, it works beautifully in in various in vitro studies of so-called three-dimensional brains, you know, or in or in retina samples. So really it captures aging of gestational age during development, you know." (said at 0:39:11)

No published record matching the claim that the original pan-tissue epigenetic clock accurately tracks gestational age during development in prenatal brain samples, 3D brain organoids, and retina samples was located; this does not prove the claim false.

0:42:28needs contextmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Genetic mutations that alter DNA methyltransferase activity in developmental disorders, such as Sotos syndrome, produce 5 to 10 year deviations in human epigenetic age.

"There are very exciting findings where people studied certain developmental disorders where where mutations deactivated DNA methyltransferase or mutation rendered it overactive, you know. And sure enough, all of these mutations in humans, you know, affect epigenetic age. And so at that level, we know it has an effect as expected, and the effect is pronounced. It could add fi It could add 5 or 10 years to a person, or or the opposite, you know." (said at 0:42:28)

The speaker accurately describes research showing that mutations in epigenetic machinery genes associated with developmental disorders markedly alter epigenetic age measured by DNA methylation clocks. In a landmark study examining patients with developmental disorders, loss-of-function mutations in NSD1 (which cause Sotos syndrome) were found to substantially accelerate epigenetic aging. However, NSD1 is technically a histone (H3K36) methyltransferase rather than a DNA methyltransferase, although H3K36 methylation directly directs and coordinates downstream DNA methylation patterns.

0:44:57supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

HIV infection is associated with accelerated epigenetic aging in humans.

"our finding that HIV is very much associated with accelerated epigenetic aging also points again to this idea of a viral component, you know." (said at 0:44:57)

Multiple longitudinal studies and a systematic review confirm that HIV infection is significantly associated with accelerated epigenetic aging in human blood and other tissues, as measured by various DNA methylation clocks (e.g., Horvath, Hannum, Levine/PhenoAge, and GrimAge). This epigenetic age acceleration is detectable from the time of initial infection.

0:46:01supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Differentiating an induced pluripotent stem cell (iPSC) into a mature cell, such as a neuron, only increases its epigenetic age by roughly one to two years.

"if you take, for example, a stem cell, an iPS cell, and then differentiate it into a more mature cell, for example a more mature neuron, you will find that the epigenetic age increases. The issue is it doesn't increase by a lot, you know. So a more differentiated cellular more mature cell maybe maybe one or two years older than the stem cell." (said at 0:46:01)

The claim that differentiating induced pluripotent stem cells (iPSCs) into derived cells, such as neurons, results in only a minimal increase in epigenetic age is supported by published evidence. Epigenetic clock analyses show that reprogramming somatic cells resets their DNA methylation age to a baseline fetal/embryonic age (near zero). While subsequent differentiation into neurons causes a slight increase in epigenetic age, the resulting cells remain at an embryonic or fetal stage (roughly zero to a couple of years of developmental age) rather than regaining adult epigenetic maturity.

0:46:26supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Direct transdifferentiation of somatic skin cells into neurons preserves the original epigenetic age of the donor skin cells.

"So you take, for example, a skin cell and you add certain factors, maybe microRNAs or what have you, and then turn the skin cell into a neuron. And this transdifferentiation protocol actually preserves the epigenetic age, you know. And so we have shown, in collaboration with several groups, that yes, the resulting neuron has the epigenetic age of the skin cell." (said at 0:46:26)

Direct reprogramming (transdifferentiation) of human skin fibroblasts directly into neurons—using factors such as microRNAs—bypasses the pluripotency stage and preserves the donor cell's epigenetic age and aging-associated transcriptomic and cellular hallmarks. When evaluated using DNA methylation-based epigenetic clocks, the epigenetic age of the induced neurons strongly correlates with and matches the epigenetic age of the starting donor fibroblasts.

0:47:42supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Cellular reprogramming using Yamanaka factors completely resets the epigenetic clock back to a prenatal stage.

"the number one proof-of-principle study is really the administration of these Yamanaka factors, because it completely resets the age, actually, to a prenatal stage, you know." (said at 0:47:42)

Cellular reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) via Yamanaka factors completely resets epigenetic aging biomarkers. In the landmark study establishing the multi-tissue epigenetic clock (Horvath clock), DNA methylation age in embryonic stem cells and iPSCs derived from somatic cells was demonstrated to be reset to near zero (prenatal/embryonic stage).

0:48:53supportedlowDr. Steve Horvath on epigenetic aging to predict healthspan:

Transient or interrupted cellular reprogramming with Yamanaka factors resets epigenetic age by several years while allowing cells to maintain their somatic identity.

"if you do it briefly for, let's say, five days, you get the benefit of rejuvenation. You may have rejuvenated the cell by 5 years or 10 years, you know, but it still remembers its identity, you know. And so... Does the epigenome reset a little bit? Like it only... Yes, yes. So a couple of groups that are working on it and have already shown that effect, you know, yes. So I analyzed fibroblasts and endothelial cells from from such an intervention. It's called sometimes interrupted reprogramming or transient reprogramming, you know. And um and and sure enough, you know, that that idea worked. It reset the age" (said at 0:48:53)

Published experimental studies confirm that transient or interrupted exposure of human somatic cells (such as fibroblasts, endothelial cells, and muscle stem cells) to reprogramming factors resets DNA methylation epigenetic clocks by several years to decades without permanently abolishing somatic cell identity. Because the evidence is derived from in vitro cell culture and preclinical laboratory models, the GRADE certainty is low.

0:52:16supportedvery lowDr. Steve Horvath on epigenetic aging to predict healthspan:

Caloric restriction slows epigenetic aging in mice, while a high-fat diet accelerates epigenetic aging in mice.

"Definitely caloric restriction slows the epigenetic clock in mice, and we know that because several groups have looked at it, including my group. All of us arrive at the same answer. Conversely, by the way, high-fat diet, you know, accelerates the epigenetic age of mice, you know." (said at 0:52:16)

Published mouse studies evaluating DNA methylation-based epigenetic clocks consistently show that caloric restriction slows epigenetic aging, whereas a high-fat diet accelerates epigenetic aging. Animal studies by multiple groups developing and validating mouse epigenetic clocks have confirmed that caloric restriction significantly decreases epigenetic age acceleration, while high-fat feeding augments age-related DNA methylation changes and epigenetic age.

0:59:23supportedlowtheir own paperDr. Steve Horvath on epigenetic aging to predict healthspan:

In an observational analysis from the Women's Health Initiative cohort, fish oil/omega-3 supplementation was associated with slower epigenetic aging according to the GrimAge clock.

"Interestingly, according to GrimAge, we did find that people who used omega-3 supplements or fish oil, they were actually aging more slowly. ... we analyzed really an observational study, and that's our problem: our study was an epidemiological study, I want to say the Women's Health Initiative. And and there we did see this association that women who took fish oil supplements were aging more slowly according to GrimAge, you know." (said at 0:59:23)

In the landmark study introducing the DNAm GrimAge epigenetic clock (Lu et al., 2019), the investigators analyzed large cohort datasets including the Women's Health Initiative (WHI) and the Framingham Heart Study to evaluate cross-sectional associations between lifestyle factors, dietary supplement use, and epigenetic age acceleration. They identified an association between omega-3/fish oil supplementation and negative GrimAge acceleration (slower biological aging relative to chronological age). Subsequent randomized clinical trial data (such as the DO-HEALTH trial) and Mendelian randomization studies have similarly observed that omega-3 intake or supplementation is associated with deceleration across second-generation DNA methylation clocks, including GrimAge.

1:02:35supportedlowDr. Steve Horvath on epigenetic aging to predict healthspan:

In the Women's Health Initiative, women with sleep disturbances had slightly accelerated epigenetic age in blood.

"We looked at um people who are—women who have sleep disturbances in the Women's Health Initiative, and sure enough, um they their age, epigenetic age of blood was slightly accelerated." (said at 1:02:35)

A 2017 cross-sectional analysis of 2,078 postmenopausal women from the Women's Health Initiative (WHI) found that self-reported insomnia symptoms (such as restlessness, trouble falling or staying asleep, and early waking) were significantly associated with advanced epigenetic age in blood (β = 1.02, p = 0.005) after adjusting for demographic and health covariates.

1:04:18supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

The blood epigenetic age of centenarians and supercentenarians is measured to be substantially younger than their chronological age, potentially up to 15 years younger.

"if you analyze the blood for from a centenarian or supercentenarian, it's true, our age estimates are really way below their chronological ages, could be 15 years younger, you know. So there's a real leveling-off effect, you know." (said at 1:04:18)

Studies measuring DNA methylation age in blood samples from centenarians and semi-supercentenarians (individuals aged 105–109) demonstrate that their epigenetic age is substantially younger than their chronological age. A study examining peripheral blood mononuclear cells (PBMCs) from 82 Italian semi-supercentenarians (mean chronological age: 105.6 years) found that their epigenetic age was on average 8.6 years younger than expected based on chronological age (with individual variation reaching up to ~15 years), and their offspring were also epigenetically younger (5.1 years younger) than age-matched controls.

1:05:09supportedvery lowDr. Steve Horvath on epigenetic aging to predict healthspan:

Growth hormone receptor knockout mice age more slowly according to mouse epigenetic clocks.

"these growth hormone knockout mice that are known to live longer, sure enough, according to the epigenetic clocks in mice, they really age more slowly." (said at 1:05:09)

Studies developing and evaluating multi-tissue DNA methylation epigenetic clocks in mice have shown that long-lived dwarf mice, including growth hormone receptor knockout (GHRKO) mice, exhibit a slower rate of epigenetic aging compared to wild-type controls.

1:06:44supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Radiation-induced cellular senescence does not accelerate epigenetic clocks.

"Then there are other forms, so-called radiation-induced senescence: you irradiate the cell, and that form of senescence doesn't seem to accelerate the epigenetic clocks, you know." (said at 1:06:44)

Published experimental work directly supports the claim. In in vitro studies evaluating DNA methylation age across different forms of cellular senescence, replicative senescence and oncogene-induced senescence were accompanied by accelerated epigenetic aging, whereas DNA damage- and radiation-induced senescence did not accelerate the Horvath epigenetic clock.

1:06:58supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

Immortalizing a cell by overexpressing TERT (telomerase reverse transcriptase) does not stop epigenetic aging, and its epigenetic age continues to increase with passaging.

"conversely, there are ways of immortalizing cells by overexpressing the component of the telomerase, the TERT. Now that—so immortalizing a cell actually doesn't stop epigenetic aging, you know. You can have an immortalized cell that you can passage for decades, but the epigenetic age keeps going up." (said at 1:06:58)

In vitro experimental studies tracking DNA methylation across extended cellular passaging demonstrate that ectopic expression of telomerase reverse transcriptase (hTERT) immortalizes human somatic cells and bypasses replicative senescence, but does not halt the progression of epigenetic aging. Epigenetic clocks (such as the Horvath DNA methylation clock) show that hTERT-immortalized cells continue to accumulate age-associated DNA methylation changes and increase in epigenetic age as they undergo successive cell divisions.

1:08:08supportedhighDr. Steve Horvath on epigenetic aging to predict healthspan:

Steve Horvath's original epigenetic clock used 353 genomic loci, while the GrimAge clock developed by Ake Lu uses over 1,000 locations in the genome.

"my original clock used 353 loci. When we look at GrimAge from Ake Lu, a scientist in my lab, it uses over 1,000 locations in the genome." (said at 1:08:08)

Steve Horvath's original pan-tissue epigenetic clock, published in 2013, was constructed using 353 CpG loci to estimate DNA methylation age. The subsequent mortality-risk epigenetic clock, DNAm GrimAge, developed by Ake T. Lu and colleagues in Horvath's laboratory, incorporates DNA methylation-based surrogate markers for plasma proteins and smoking history that encompass 1,030 unique CpG locations in the genome.

1:08:45needs contextmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

The human genome contains approximately 28 million cytosine locations, roughly a quarter of which change methylation status with age.

"And when you look at the genome, and we have in principle 28 million locations in the genome are cytosines, you know, and I want to say a quarter of them change with age." (said at 1:08:45)

The speaker's figure of approximately 28 million sites refers specifically to CpG dinucleotide methylation sites in the human genome, rather than all genomic cytosines (which total over 600 million base pairs across the ~3.1 billion base pair haploid genome). Published literature confirms that the human methylome consists of roughly 28 million CpG dinucleotides where DNA methylation typically occurs, and a substantial proportion of these sites undergo progressive alterations in methylation level across the lifespan (age-associated epigenetic drift and clock CpGs).

1:09:32supportedhighDr. Steve Horvath on epigenetic aging to predict healthspan:

DNA methylation sites that gain methylation with aging are enriched in Polycomb group protein target sites.

"sites that gain methylation with aging um are known to be located in so-called Polycomb group protein target sites, so certain proteins that play a very important role in maintaining stem cells, you know." (said at 1:09:32)

Published genomic analyses across human tissues and diverse mammalian species consistently demonstrate that CpG sites that undergo age-associated hypermethylation are substantially enriched at Polycomb group target genes (such as Polycomb Repressive Complex 2 / PRC2 binding sites), which play a central role in maintaining stem cell pluripotency and regulating developmental gene expression.

1:09:53supportedmoderateDr. Steve Horvath on epigenetic aging to predict healthspan:

DNA methylation sites that lose methylation with aging are enriched in enhancer regions.

"The sites that lose methylation um also are enriched with certain themes, for example, often they're in so-called enhancer regions, you know." (said at 1:09:53)

Epigenome-wide association studies across human tissues and mammalian model organisms consistently demonstrate that DNA methylation sites undergoing age-associated hypomethylation (loss of methylation) are significantly enriched within non-CpG island regulatory domains, particularly enhancer and super-enhancer regions, whereas age-associated hypermethylation predominantly clusters at promoter CpG islands and Polycomb-repressed chromatin regions.

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