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From Issue #6 December 20, 2012

Genetic Shoelaces Told My Demise

A protective structure at the end of chromosomes may be key to predicting — and changing — our lifespan.

By Mark Harris Twitter icon 


Every one of the roughly 50 trillion cells in your body contains a ticking biological clock counting down your mortality. We can’t yet read the clock’s face to reckon your expiration date, but some scientists now believe they have deciphered at least part of the message and can predict about how long people with the clock’s hands set like yours might live. You might even be able to hit the snooze button and improve the odds of a longer life.1

These cellular clocks are called telomeres, tiny genetic structures found on the ends of chromosomes, and they are often compared to the protective aglets on shoelaces.2 Every time a cell divides and reproduces, the telomeres fray and get a little shorter. When telomeres become very short, cells either shut down or die.

Some scientists say their research shows that, in practice, telomeres respond to every beer drunk, cigarette smoked, vegetable chomped, and marathon run, recording them for posterity in every cell in the human body. They claim that peeking at this hidden data stream using simple medical tests can reveal one’s true biological age and even life expectancy. To be fair, other researchers rate the results no better at predicting mortality than the length of the crease between one’s thumb and one’s wrist.

To thy own quantified self, be true

The quantified self movement may help thousands improve their fitness and break bad habits by digitally tracking their daily activities for later analysis, but there’s no denying that the process is tedious. There’s the Garmin to charge, the FitBit to sync, and the Nike+ app to open, to say nothing of even nerdier accessories. (To judge by the stupendously unattractive Zeo sleep-management headband, a quantified couples movement is unlikely to emerge any time soon.)

How much easier it would be if telomere measurement could accurately quantify one’s biological well-being without relying on satellites, smartphones, or Velcro’d gadgets. I have dabbled in most of the life-logging gear on the market, and like many quantified selfers, I mailed off a tube of spittle to 23andMe long ago. I got back my genetic profile, detailing my ancestral lineage, carrier status, and likelihood of suffering conditions from the life-threatening to the borderline comical. I discovered, among other things, that I have a slightly higher than average risk of suffering coronary heart disease, no breast cancer mutations to pass on, and a propensity for my earwax to be of the wet variety.

Exciting stuff. But 23andMe lacks that crucial feedback loop that sustains the measuring of one’s every move. With my genetic destiny so mercilessly exposed, I couldn’t reproduce the self-congratulatory glow of “crushing” (as Nike+ would have it) a previous best run, or bask in the knowledge, transmitted wirelessly from smart bathroom scales, that I had succeeded in keeping my body fat percentage to that of an emaciated teenager. I was either going to develop restless leg syndrome (a 1.5% probability) or I was not — end of story.

What could make telomeres irresistible to selfers is that, unlike our genetic code, they are definitely not static and they may even be partially under our control.

Aglet examination

Short telomeres have been linked to age-related conditions such as heart disease, stroke, osteoporosis, and dementia. Elderly people with the shortest telomeres are up to three times as likely to die from heart disease or develop cancer. A recent study of over 100,000 older Californians by Kaiser Permanente found that those with the shortest telomeres (in the 10th percentile and under) were nearly a quarter more likely to die in the three years following measurement than the rest.

Telomeres were discovered in the 1970s, earning a Nobel prize for Australian scientist Dr. Elizabeth Blackburn. But only recently have consumer tests become available. One day last summer I visited a local phlebotomist, had him draw a small amount of blood, and shipped it via overnight delivery to SpectraCell’s laboratory in Houston, Texas. SpectraCell was the first company to offer commercial telomere length testing in the US, and a one-off test there runs about $300. Dr. Blackburn herself has set up a company, Telome Health, that intends to market a simpler saliva test for telomere length early in 2013, probably priced significantly lower than SpectraCell’s.

Both are PCR (polymerase chain reaction) assays, commonly used in paternity tests and DNA fingerprinting, with SpectraCell claiming a margin of error of around 8%. Both companies provide patients with a report comparing their telomere length to the average for that chronological age. According to SpectraCell’s vice president Otto Schaefer, “It can serve as a wake-up call if you’re aging faster than others in your age range.” Telome Health goes so far as to say that telomere length can predict future years of healthy life.

But just how useful are these tests? And once one has an inkling of one’s possible demise, is there anything that can postpone the inevitable? Dr. Paul Shiels, a lecturer on aging at the University of Glasgow in Scotland, measured the telomeres of nearly 400 Glaswegians over a 10-year period. The results were shocking. After a decade, he found that telomeres had shortened by around 8% in people who earned less than $40,000, but only 0.6% in people with higher incomes. There were also disparities between those living in rented accommodations and those living in their own homes, and for people eating a poor rather than a healthy diet.

“Social status and deprivation play a major part in how quickly people age and develop disease,” says Shiels. “Telomere tests are great for a public health intervention when you want some sort of readout of how you’re doing.” Another supporter of telomere testing is Bill Andrews, founder of Sierra Sciences, a biotechnology company based in Reno, Nevada. “A lot of people out there are suffering from a severe telomere length problem and don’t know it,” he says. “Plenty of 30-year-olds could have the telomere lengths of a 60-year-old. These tests will show that.”

The risks of knowing

With the introduction of Telome Health’s quick, painless, and (relatively) cheap saliva assay, some experts expect a boom in consumer testing. “People will like to say that they’ve got the telomeres of a 20-year-old, as a sort of trophy,” says Dr. Tim Spector of King’s College London. “I could also see lawyers being interested in divorce cases — a before-and-after test. It’s a hot topic whether chronic stress is a factor in telomere length.”

Americans are protected by the 2008 Genetic Information Nondiscrimination Act (GINA), which forbids insurers from denying coverage or charging higher premiums based on genetic test results. It also prevents most employers from discriminating against employees. But there are worries that telomere testing could still be abused. Companies with fewer than 15 employees are exempt from GINA, and the legislation doesn’t cover, say, checking a prospective partner before a wedding.

The hook for hard-core quantified selfers is that telomere length does not appear to be a one-way street. Numerous studies have shown that giving up smoking and drinking, improving your diet, reducing stress, and getting more exercise (but not too much) can lengthen telomeres over time. “Eating a balanced diet with fruit and vegetables is akin to putting high-grade gas in the car. It doesn’t have a spectacular or immediate effect but over a lifetime can act as a screen to prevent damage,” says Dr. Shiels.

However, such general preventive advice is already well known — and poorly followed. A third of adults in the US are clinically obese, and even the growing quantified self movement is unlikely to prevent that from rising to almost half by 2030.3 Scientists are now looking for treatments that can reverse telomere shortening without people having to forgo their unhealthy lifestyles.

Just add telomerase

Bill Andrews was one of the first to identify human telomerase, an enzyme that increases the length of telomeres in reproductive cells, allowing children to be born with fully developed protective coating. He hopes that by stimulating the production of telomerase throughout the body, people will live longer, healthier lives. “I wouldn’t be surprised if we suddenly saw people living to be 150 or longer,” he said.

Andrews’s company, Sierra Sciences, has screened over 300,000 chemicals for their ability to activate telomerase and has already found a handful of candidates. Such anti-aging drugs will not come cheap. The only telomerase activator available now, TA-65, costs up to $1,200 for a six-month supply and has not actually been shown to increase the average length of telomeres. Despite this, Andrews swears by it.

He said, “I’m an ultra-marathon runner. Three weeks after taking TA-65, I went from the back of the pack to being a front-runner. I often win my age group now.” While TA-65 may have made Andrews feel younger and fitter, his average ranking among runners seems to have decreased in the years following his starting use of the compound in mid-2007.

Andrews’s views and claims are on the periphery; mainstream researchers remain skeptical. “Telomerase is a bit too much of a machine gun,” says Tim Spector. “It’s going to affect far too many other mechanisms, and it’s going to have major side effects, the most obvious being that you increase the risk of every cancer.”

The only time that human cells produce extremely high levels of telomerase in nature, becoming truly immortal, is in the rampant growth of cancer. In fact, several researchers are taking the opposite approach to Andrews. They are developing telomerase inhibitors that shut down the production of telomerase in cancerous cells, forcing them to die out rather than endlessly reproduce. “There’s a good reason we don’t have telomerase in our normal cells,” says Paul Shiels. “It allows our telomere clock to tick down naturally and prevent the spread of damaged cells.”

Omega man

So how far down has my biological clock ticked? As a skinny 41-year-old non-smoker, I was hoping for a reasonably good result. Infants typically have around ten kilobasepairs of telomeres, while 80-year olds might have fewer than six. It turns out that my telomere length is just over eight kilobasepairs — about average for a 33-year old.

Does that mean I can expect to live eight years longer than others my age? Sadly not, says Tim Spector. “Some people with high telomeres die at 50, while others with low telomeres live perfectly normal, healthy lives. As a group, it’s useful for science. But for predicting when an individual’s going to die, it’s useless.”

Useless or not for funeral planning, SpectraCell carries out hundreds of consumer blood tests a month, and Telome Health hopes its numbers will soar into the thousands once its cheaper, needle-free system arrives next year.

Dr. Blackburn’s company makes the uncertainty of telomere testing an asset. Its interim CEO, Dan Hunt, once told me, “More interesting than just getting one test is to test every six months, so people can see the results of stress reduction, exercise, and changes to their diet. We’d like to see people adopt telomere testing as a monitoring technology.”

Of course they would, and something tells me that we quantified selfers are going to be their very best customers.

Photo of gene chips/microarrays via the National Institutes of Health.

  1. Estimates put the human body’s cell count at between 10 and 100 trillion. Biological anthropologist Greg Laden suggests that the range for adults is approximately 46 to 68 trillion. This number excludes bacteria and other co-residents, which could number 10 quadrillion. 

  2. An aglet is the name of that thing that you know you should know the name of that protects the end of your shoelace in a little cylinder of plastic. Telomere, the singular form, is pronounced like “tell a mere.” 

  3. The only positive note on this score appeared last week, when the New York Times reported that several major cities had seen unexpected, significant, and verifiable dips in childhood obesity. The reasons are so far unknown. 

Mark Harris averages 7.18 minute miles running, 15.8 mph on long distance bike rides, has 6.2% body fat and has telomeres that are 8.08 kilobasepairs long and shrinking. He has written 104 stories for The Sunday Times in London, 31 features for The Economist and 1 for The Magazine. He lives in 98103. His website is shamefully neglected.

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