Does Telomere Length Determine Lifespan? Short Telomeres Track With Earlier Death. The Genetics Say Longer Ones Raise Cancer Risk.
Does telomere length determine lifespan? Not on its own, and not in the simple way the supplement aisle suggests. In large population studies, people with the shortest telomeres in their white blood cells die sooner. In a Copenhagen study of 64,637 adults, the shortest tenth had a 40 percent higher risk of death than the longest tenth over follow-up of up to 22 years. But when researchers use inherited gene variants to ask whether telomere length itself causes that risk, the answer splits in two. Genetically longer telomeres lower the risk of coronary heart disease and raise the risk of several cancers, and they show little link to how long people's parents lived. That split matters for anyone interested in telomerase activators such as epithalon, which lengthened telomeres in cell culture. This article walks through the cohort data, the Mendelian randomization studies, a 2023 report on a family with inherited long telomeres, and what the evidence does and does not say about trying to lengthen telomeres on purpose. It is educational, not medical advice.
Key Takeaways: Telomere Length and Lifespan
In 64,637 Danish adults, people in the shortest decile of white blood cell telomere length had an all-cause mortality hazard ratio of 1.40 compared with the longest decile (Rode and colleagues, Journal of the National Cancer Institute, 2015). In the same Danish study, gene variants that shorten telomeres were linked to lower cancer mortality and showed no link to all-cause mortality. Short telomeres predicted death, but inherited short telomeres did not. A Mendelian randomization study of 35 cancers and 48 other diseases found that genetically longer telomeres raised the odds of glioma by 5.27 times and lung adenocarcinoma by 3.19 times per standard deviation, while lowering coronary heart disease odds to 0.78 (Telomeres Mendelian Randomization Collaboration, JAMA Oncology, 2017). In 379,758 UK Biobank participants, genetically longer telomeres showed little association with parental lifespan or having a centenarian parent (Kuo and colleagues, Aging Cell, 2019). Epithalon induced telomerase and lengthened telomeres in human fibroblasts in culture. No human trial has shown that lengthening telomeres with any compound extends lifespan.
Does telomere length determine lifespan?
Telomere length predicts lifespan in population studies, but it does not determine it. Short telomeres in white blood cells go with a higher risk of death, yet the genetic evidence suggests telomere length is one factor that shifts risk between diseases rather than a master clock that sets how long a person lives. Telomeres are the repeating DNA caps on the ends of chromosomes. They shorten a little each time most cells divide, and when they get too short the cell stops dividing. That makes telomere length an appealing candidate for a biological clock. The problem is that a measurement can predict death without causing it. People with short telomeres may also smoke more, carry more inflammation or have more chronic disease, and those things could shorten telomeres and shorten life separately. To separate the two, researchers use two tools. Twin studies compare people who share genes and upbringing. Mendelian randomization uses gene variants that set telomere length at conception, which are not changed by later habits or illness. Both tools tell a more complicated story than the cohort data alone.
Measured Short Telomeres Predict Death. Inherited Short Telomeres Do Not.
Hazard ratios; 1.0 means no difference. Sources: Rode and colleagues, Journal of the National Cancer Institute, 2015; Bakaysa and colleagues, Aging Cell, 2007.
How much does short telomere length raise the risk of death?
Short telomere length raises the measured risk of death by roughly 40 percent at the extremes of the population. In the Copenhagen City Heart Study and the Copenhagen General Population Study, 64,637 people had telomere length measured by quantitative PCR. Over follow-up of 0-22 years, with a median of 7 years, 7607 people died. Those in the shortest telomere decile had a multivariable-adjusted hazard ratio of 1.40 (95% CI 1.25 to 1.57) for all-cause death compared with the longest decile, and results were similar for cancer and cardiovascular death. A Swedish twin study tested whether shared genes or upbringing explain the link. Comparing twins within each pair, the twin with the shortest telomeres had about three times the risk of death of the co-twin with the longest, a hazard ratio of 2.8 (95% CI 1.1 to 7.3), according to Bakaysa and colleagues in Aging Cell in 2007. The wide confidence interval reflects a small sample, but the within-pair design rules out family background as the whole explanation. These are associations. They show that telomere length is a useful marker of risk. They do not show that a person who lengthened their telomeres would gain the matching years.
What happens when genetics decides telomere length?
When telomere length is set by inherited genes, the link with overall death largely disappears. The Copenhagen researchers scored each person on three gene variants, in TERC, TERT and OBFC1, that shorten telomeres. Each shortening allele cut telomere length by 69 base pairs (95% CI 61 to 76). If short telomeres caused early death, people born with more shortening alleles should have died sooner. They did not. The allele score was not associated with cardiovascular, other or all-cause mortality. It was associated with lower cancer mortality, with a hazard ratio of 0.95 (95% CI 0.91 to 0.99) per allele. Rode and colleagues concluded that genetically determined short telomeres were associated with low cancer mortality but not with all-cause mortality. The most likely reading is that much of the observed link between short telomeres and death runs the other way or through shared causes: illness, inflammation and other aging processes wear telomeres down in blood cells, and the shortened telomeres flag that damage.
Do longer telomeres raise cancer risk?
Yes. Genetically longer telomeres raise the risk of several cancers, and for some rare cancers the effect is large. The Telomeres Mendelian Randomization Collaboration analysed summary data from 103 genome-wide association studies covering 35 cancers and 48 non-cancer diseases, with 420,081 cases and 1,093,105 controls. Per one standard deviation of genetically longer telomeres, the odds ratios were 5.27 for glioma, 4.35 for serous low-malignant-potential ovarian cancer, 3.19 for lung adenocarcinoma, 2.98 for neuroblastoma, 2.19 for bladder cancer, 1.87 for melanoma, 1.76 for testicular cancer, 1.55 for kidney cancer and 1.31 for endometrial cancer. The authors noted that associations were stronger for rarer cancers and in tissues where stem cells divide less often. The biology fits. Telomere shortening is one of the brakes that stops a damaged cell from dividing indefinitely. A cell that starts with longer telomeres can divide more times before that brake engages, which gives a cell carrying cancer-driving mutations more chances to grow.
Genetically Longer Telomeres Raise the Odds of Nine Cancers
Odds ratio per 1 SD of genetically longer telomere length. Source: Telomeres Mendelian Randomization Collaboration, JAMA Oncology, 2017.
Do longer telomeres protect the heart?
Longer telomeres appear to protect against coronary heart disease and a few other conditions. In the same 2017 Mendelian randomization study, each standard deviation of genetically longer telomeres was linked to an odds ratio of 0.78 for coronary heart disease, 0.63 for abdominal aortic aneurysm, 0.42 for celiac disease and 0.09 for interstitial lung disease. For most psychiatric, autoimmune, inflammatory and diabetic conditions there was little evidence of any effect. A UK Biobank analysis by Kuo and colleagues in Aging Cell in 2019 reached the same split with a different method. Using 13 gene variants in 379,758 participants aged 40-70, followed for a mean of 7.5 years, it estimated effects per 250 base pairs of longer telomere, which the authors described as roughly the average change over a decade. Coronary heart disease odds fell to 0.95 and cancer odds rose to 1.11.
The Same Genes Lower the Odds of Four Non-Cancer Diseases
Odds ratio per 1 SD of genetically longer telomere length; below 1.0 means lower risk. Source: Telomeres Mendelian Randomization Collaboration, JAMA Oncology, 2017.
Do people with longer telomeres live longer overall?
The genetic evidence that longer telomeres add years overall is weak. In the Kuo study, genetically longer telomeres showed little evidence of association with parental lifespan, centenarian status of parents, cognitive function, grip strength, sarcopenia or falls. The authors concluded that telomere lengthening may offer little gain in later-life health status and face increasing cancer risks. A larger UK Biobank study by Codd and colleagues in Nature Genetics in 2021 measured telomere length in 472,174 participants and identified 197 independent variants at 138 genomic loci. It estimated that at age 40, people with telomeres more than 1 standard deviation shorter than the population mean had a 2.5-year lower life expectancy than people 1 standard deviation or more longer. That is a real difference, though it compares the two tails of the population, not what an individual could change. A 2020 PLoS One analysis by Protsenko and colleagues set the cancer and non-cancer effects side by side using population disease rates. Long genetic telomere length was tied to an excess 94.04 cases per 100,000 people per standard deviation across 9 cancers. Short genetic telomere length was tied to 121.49 excess cases per 100,000 across 4 non-cancer diseases. Measured as disability-adjusted life years, the totals were 1255.25 and 1007.75. The authors concluded that long and short telomere length carry disease burden of approximately equal magnitude.
Long and Short Telomeres Carry a Similar Disease Burden
Excess cases and disability-adjusted life years per 100,000 people per SD of genetic telomere length. Source: Protsenko and colleagues, PLoS One, 2020.
What happens to people born with very long telomeres?
People born with very long telomeres because of POT1 gene mutations develop more tumors and blood cell disorders, according to a 2023 study in the New England Journal of Medicine. DeBoy, Armanios and colleagues at Johns Hopkins followed 17 carriers of loss-of-function POT1 mutations and 21 relatives without them, then added 6 more carriers. Among carriers whose telomeres were measured, 9 of 13 had telomeres above the 99th percentile. Carriers had benign and malignant tumors in many tissues, plus lymphomas and myeloid cancers. Five of 18 (28%) had T-cell clonality and 8 of 12 (67%) had clonal hematopoiesis of indeterminate potential, an expansion of mutated blood cells that raises the risk of blood cancer. Unlike their relatives, carriers maintained telomere length over 2 years instead of losing it with age. The authors wrote that short telomere syndromes cause age-related disease, but whether long telomeres are an advantage was poorly understood. In this family, they concluded, cancer risk was mediated by extended cellular longevity. It is one family with a rare mutation, but it is a direct look at what lifelong long telomeres can do.
What Lifelong Long Telomeres Looked Like in POT1 Carriers
Carriers with each finding versus carriers tested. Source: DeBoy and colleagues, New England Journal of Medicine, 2023.
- With finding
- Tested
How fast do telomeres shorten with age?
Telomeres shorten slowly and unevenly with age, and a single measurement is a noisy guide to biological age. A 2023 meta-analysis by Ye and colleagues in Ageing Research Reviews pooled 414 study samples covering 743,019 people aged 0-112. The pooled correlation between telomere length and age was -0.19, which is weak. Two people of the same age can have very different telomere lengths. In studies reporting base pairs, the median rate of change was -23 base pairs per year across cross-sectional samples and -38 base pairs per year in longitudinal samples that followed the same people. The shortening rate slowed until about age 50, then stayed fairly stable. The measurement method and tissue type changed the results, which is one reason commercial telomere tests are hard to compare. For context, the Kuo study treated 250 base pairs as roughly a decade of average change. Inherited variation between people is often larger than what a decade of aging takes away.
What does this mean for epithalon and telomerase activators?
The telomere evidence does not support the idea that lengthening telomeres will extend human life, and it raises a cancer question that no telomerase activator trial has answered. Epithalon, the tetrapeptide Ala-Glu-Asp-Gly, induced the catalytic subunit of telomerase, telomerase activity and telomere elongation in telomerase-negative human fetal fibroblasts in culture (Khavinson and colleagues, Bulletin of Experimental Biology and Medicine, 2003). A follow-up cell study from the same group reported that fetal lung fibroblasts which stopped dividing at passage 34 made 10 extra divisions, reaching 44 passages, when treated with epithalon (Khavinson and colleagues, 2004). These are cell culture results from a single research group. They show a mechanism, not a health outcome. The genetic data cut both ways for that mechanism. Inherited longer telomeres track with less coronary heart disease and more of several cancers, and families with very long telomeres develop tumors. Whether a short course of a telomerase activator in adulthood behaves like lifelong inherited long telomeres is unknown. Our epithalon guide (epithalon.com/blog/epithalon-peptide-longevity-telomere) covers the human studies that exist, and our review of hyperbaric oxygen (epithalon.com/blog/hyperbaric-oxygen-telomere-length-aging-evidence) shows how telomere claims can outrun trial design.
Is a telomere test worth getting?
A telomere test has limited value for an individual. Telomere length predicts mortality across large populations, but the correlation with age is weak, the result varies with the lab method and tissue, and the genetic evidence suggests that a short result mostly flags other damage rather than being the damage itself. Measures that respond to change and connect to outcomes tend to be more useful. Blood pressure, ApoB, fasting glucose, fitness and grip strength each have direct links to disease risk and each can be tracked over time. Our articles on grip strength (epithalon.com/blog/grip-strength-mortality-predictor-men-evidence) and ApoB (epithalon.com/blog/apob-vs-ldl-cholesterol-men-heart-risk-evidence) cover two of them. Anyone who gets a telomere test should treat it as one data point, ask which method the lab used, and avoid making treatment decisions on that number alone.
Where do the figures in this article come from?
Every figure in this article comes from a source checked during research. Copenhagen cohorts: Rode, Nordestgaard and Bojesen, Journal of the National Cancer Institute, 2015 (doi.org/10.1093/jnci/djv074). Swedish twins: Bakaysa and colleagues, Aging Cell, 2007 (doi.org/10.1111/j.1474-9726.2007.00340.x). Cancer and non-cancer odds ratios: Telomeres Mendelian Randomization Collaboration, JAMA Oncology, 2017 (doi.org/10.1001/jamaoncol.2016.5945). UK Biobank Mendelian randomization: Kuo and colleagues, Aging Cell, 2019 (doi.org/10.1111/acel.13017). UK Biobank genetics and life expectancy: Codd and colleagues, Nature Genetics, 2021 (doi.org/10.1038/s41588-021-00944-6). Disease burden: Protsenko and colleagues, PLoS One, 2020 (doi.org/10.1371/journal.pone.0240185). POT1 family: DeBoy and colleagues, New England Journal of Medicine, 2023 (doi.org/10.1056/NEJMoa2300503). Telomere shortening meta-analysis: Ye and colleagues, Ageing Research Reviews, 2023 (doi.org/10.1016/j.arr.2023.102031). Epithalon cell studies: Khavinson and colleagues, Bulletin of Experimental Biology and Medicine, 2003 (doi.org/10.1023/a:1025493705728) and 2004 (doi.org/10.1023/b:bebm.0000038164.49947.8c).
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