In light of a recent New York Times article, https://www.nytimes.com/.../long-telomeres-age-
longevity..., which had a misleading title and subtitle, we feel that clarification of the realities
of telomeres in humans is necessary to prevent misinformation and confusion.
To cut to the chase: the many population-based studies on this topic overwhelmingly show
that long telomeres predict longer life, and none show that long telomeres shorten life.
Below, we summarize the relevant extensive scientific evidence about the roles and impacts
of telomeres in humans:
It has long been known that short telomeres limit cell division and predict some
degenerative diseases of aging whereas long telomeres permit, and predict, cell replication
and thus lead to higher risk of some cancers. As might be expected from this, multiple
studies find increased disease risks at either end of the telomere length spectrum in normal
human populations. See, for example,
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7544094/.
Telomere length is determined by a combination of both genetic and non-genetic factors.
In humans, normal small genetic variations that cause telomeres to be shorter than average
increase the risks of immune system problems, heart and lung disease and a variety of
degenerative diseases including Alzheimer’s. And the normal small genetic variations that
instead make telomeres longer than average increase risks for several kinds of cancers.
These common genetic determinants of telomere maintenance in populations (genes
affecting telomerase or telomeres) impose essentially equal health burdens of longer
telomeres (for cancers) vs. shorter telomeres (for other diseases of aging),
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7544094/. Humans thus have evolved a
genetic trade-off, with the health and mortality burdens imposed by cancer versus non-
cancer partially balancing each other out. Yet, as it turns out, the net result of this trade-off
is that, overall, shorter telomeres caused by normal genetic variation predict lower life
expectancy (https://pubmed.ncbi.nlm.nih.gov/34611362/). We speculate that this genetic trade-off for telomere maintenance might help explain the
long-puzzling “cancer paradox”, in which older people with dementias are protected from
cancers, and vice versa, https://alzres.biomedcentral.com/.../s13195-022-01090-9.
Importantly, as well as the genetic influence, telomere length is also determined non-
genetically. Several healthful behaviors are linked to longer telomeres. An important
example of this is exercise. Across multiple studies, the preponderance of evidence
(coming from both observational and intervention studies) links longer telomeres with more
aerobic exercise (https://pubmed.ncbi.nlm.nih.
While the biological mechanisms connecting the two are likely to be complex, it is
important to be aware that exercise has NEVER been found to increase cancer risks – in
fact, the opposite is true. As the National Cancer Institute states: “There is strong evidence
that higher levels of physical activity are linked to lower risk of several types of cancer.”
More information from the National Cancer Institute about the protective effect of exercise
against cancer can be found on their website: https://www.cancer.gov/.../physical-activity-
fact-sheet.
Elizabeth Blackburn, PhD
Elissa Epel, PhD
Jue Lin, PhD
References
Aviv A, Shay JW. Reflections on telomere dynamics and ageing-related diseases in humans. Philos Trans R Soc Lond B Biol Sci. 2018 Mar 5;373(1741):20160436. doi: 10.1098/rstb.2016.0436. PMID: 29335375; PMCID: PMC5784057.
https://pubmed.ncbi.nlm.nih.gov/29335375/
Buttet M, Bagheri R, Ugbolue UC, Laporte C, Trousselard M, Benson A, Bouillon-Minois JB, Dutheil F. Effect of a lifestyle intervention on telomere length: A systematic review and meta-analysis. Mech Ageing Dev. 2022 Sep;206:111694. doi: 10.1016/j.mad.2022.111694. Epub 2022 Jun 26. PMID: 35760212.
https://pubmed.ncbi.nlm.nih.gov/35760212/
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https://www.nature.com/articles/ng.2528
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https://pubmed.ncbi.nlm.nih.gov/34611362/
Protsenko E, Rehkopf D, Prather AA, Epel E, Lin J. Are long telomeres better than short? Relative contributions of genetically predicted telomere length to neoplastic and non-neoplastic disease risk and population health burden. PLoS One. 2020 Oct 8;15(10):e0240185. doi: 10.1371/journal.pone.0240185. PMID: 33031470; PMCID: PMC7544094.
https://pubmed.ncbi.nlm.nih.gov/33031470/
Song S, Lee E, Kim H. Does Exercise Affect Telomere Length? A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Medicina (Kaunas). 2022 Feb 5;58(2):242. doi: 10.3390/medicina58020242. PMID: 35208566; PMCID: PMC8879766.
https://pubmed.ncbi.nlm.nih.
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