Telomeres are maintained by the enzyme telomerase. This adds to the telomeres, preventing them from shortening as rapidly, thereby allowing the cells to live for longer. A good thing, perhaps, until we learn that cancer cells have increased amounts of telomerase, which allows them to continue dividing.

Sebnem Unluisler, genetic engineer and chief longevity officer at the London Regenerative Institute in the United Kingdom, told Medical News Today:

“Studies have demonstrated a correlation between telomere length and biological age. Generally, shorter telomeres are associated with advanced chronological age and increased susceptibility to age-related diseases. Moreover, individuals with certain genetic variations or lifestyle factors that accelerate telomere shortening tend to exhibit a more rapid aging phenotype.”

Telomere length has been likened to a “biological clock,” with shorter telomeres indicative of greater biological age. Several lifestyle factors have been associated with shorter telomeres. One is a lack of physical activity.

In one study, sedentary women were found to have telomeres that indicated they were biologically 8 years older than women of the same chronological age who exercised more.

Tobacco smoking increases the risk of many diseases, and it also accelerates the shortening of telomeres. A study found that telomere shortening was enhanced in the circulating white blood cells of smokers, increasing the rate of biological aging.

Getting insufficient sleep can also influence telomere length, shortening telomeres even in childhood, which may lead to impaired health.

“Recent studies have suggested that telomere length alone may not be a reliable predictor of lifespan or aging. For example, some individuals with shorter telomeres have been found to live longer than those with longer telomeres. Other factors, such as lifestyle, environment, genetics, and stress also play a role in aging and disease.”

– Dr. Joshua Berkowitz, medical director at IV Boost UK

Shorter telomeres may be associated with shorter lifespans and more rapid biological aging, but are longer telomeres therefore associated with longer lifespans and healthier aging? The evidence is not conclusive.

Many lifestyle factors that are associated with better health are also associated with telomere length.

A diet rich in legumes, wholegrain, and fresh fruit and vegetables, such as the Mediterranean diet, is positively associated with telomere length in several studies. The positive effects of the Mediterranean diet on telomeres may be due to its antioxidant and anti-inflammatory properties.

Physical activity is advisable for general health, but the evidence for the effect of physical activity on telomere length is not clear-cut — although exercise is thought to be beneficial, the optimal exercise dose is unclear.

One study found that moderate exercise helps maintain telomere length, but the benefits decrease with excessive exercise; others found an effect only in people taking extreme amounts of exercise, such as ultra-marathon runners.

Other studies have shown that getting enough sleep, never having smoked tobacco, and avoiding stress may help preserve telomere length.

“While previous research has suggested that longer telomeres may be associated with longevity, most of this research has been done in cells, and it is not yet clear whether longer telomeres in humans are a cause or a consequence of healthy aging.”

— Sebnem Unluisler

One study even found that telomeres at both extremes — much longer or shorter than average — were associated with susceptibility to diseases. Short telomeres were linked to organ failure, and long ones to a variety of cancers.

Now, a new study has shown that longer telomeres may not be the key to healthy aging. It suggests, instead, that long telomeres allow cells with age-related mutations to live longer, increasing the likelihood of tumors and other chronic health conditions.

The study, which looked at people with a mutation (POT1) that causes longer telomeres, found that, while some showed signs of youthfulness, such as no gray hair in their 70s, those with the mutation had a higher incidence of benign and cancerous tumors, as well as the age-related blood condition clonal hematopoiesis, which increases the risk of several cancers, than those without.

One of the authors, Dr. Mary Armanios, professor of oncology at the Johns Hopkins Kimmel Cancer Center, and professor of genetic medicine, molecular biology and genetics, and pathology at the Johns Hopkins University School of Medicine, suggests an explanation.

According to her, “[c]ells with very long telomeres accumulate mutations and appear to promote tumors and other types of growths that would otherwise be put in check by normal telomere shortening processes.”

Sebnem Unluisler commented that “[t]his study suggests that there may not be a simple relationship between telomere length and aging.”

”While longer telomeres may be associated with increased cancer risk, they may also be associated with decreased risk of other age-related diseases and improved overall health,” she noted.

Telomere length may not depend solely on the influence of external factors either, as evidence increasingly suggests.

A study published in Science in April 2024 examined telomere lengths in 147 participants using an innovative method called “Telomere Profiling.”

It found that the telomeres “bookending” specific chromosomes were “consistently longer or shorter,” and that these differences in telomere length across different chromosomes occurred in newborn chord blood, too.

This, the study authors explain, suggests that “telomere length is determined at birth and that chromosome end–specific telomere length differences are maintained as telomeres shorten with age.”

The finding contradicts previous notions about telomeres, which held that these “caps” had fairly consistent average lengths that did not vary across all chromosomes.

Senior author Carol Greider, PhD, Distinguished Professor of Molecular, Cell, and Developmental Biology at UC Santa Cruz, qualified the finding as “jaw dropping” in a press release.

The good news, according to the research team behind this study, is that other researchers and clinicians will be able to use their Telomere Profiling tool to help them improve diagnostics and develop new and better drugs.

Although longer telomeres are associated with longevity in cells, the evidence is not conclusive that they are the key to longer, healthier lives. However, many of the lifestyle factors that reduce the risk of disease also result in longer telomeres.