A few months ago my friend Steve announced his plan to live to 150.
Steve is no gerontologist – he sells data management software to corporate clients – but in his spare time he's been reading up on longevity and blogging about what he's learned. His goal is to make the most of what science has to offer to reach a record-breaking lifespan.
It's ambitious, but not that far-fetched, he says. Just last week the oldest man ever, Jiroemon Kimura, died at 116. Given the pace of medical discovery maybe someone will get to 150 some day. Why not Steve?
It's certainly easy to understand his motivation. Like me, Steve was born at the tail end of the baby boom. In a little more than 18 months, every last straggling member of that historic cohort will finally hit age 50. For our demographic, longevity is no longer an abstract concept. And just in case we're not thinking about it enough, there's an anti-aging industry doing all it can to cash in on our anxieties.
Into this carnival of hormone therapies and supplements comes an increasingly accessible test that promises to show just how well (or poorly) we're holding up against the ravages of time.
It involves telomeres – which, if you haven't had to think about this yet, are tiny structures at the ends of your chromosomes that keep them from fraying and losing crucial bits of genetic information. What interests researchers who study aging is that when cells divide, their telomeres get shorter. Once they get too short, cells stops dividing and may die. Played out across the whole body, there's mounting evidence that shorter telomeres translate into increased susceptibility to diseases and the gradual wearing out of tissues that is the hallmark of old age.
It's tempting to think of our telomeres as the cellular equivalents of the grim reaper's hourglass, counting out our predetermined life spans. But the hourglass can get periodic refills – thanks to an enzyme called telomerase, which acts to build telomeres back up. And the rise of telomere testing for consumers is also pegged to evidence that telomere length is not just an inherited inevitability but may be influenced by factors such as stress, exercise and nutrition. The thinking is, if you can regularly monitor your telomere length, you'll be more apt to do the right things to slow the rate at which they're burning away.
"We all want to live healthier, longer," says Calvin Harley, a telomere researcher and CEO of Telome Health, a company based in Menlo Park, Calif., that offers telomere testing to consumers. "Measuring telomere length and allowing individuals to see if their cellular age is more advanced than their chronological age may be a motivation to improve lifestyle."
I can only hope.
As a working journalist in my late 40s I've hardly lived a life of serenity. Years of deadline pressures and lost sleep have surely taken their toll, along with with a general lack of exercise and too many late- night refrigerator raids. Now with three young children at home and all the usual pressures of midlife, I can easily imagine my telomeres burning up like so many sparklers.
Yet I'm also fascinated by the possibility that aging is more than just a collection of symptoms such as aching joints and greying hair. The idea that there is a mechanism that accounts for why our bodies run down is compelling. The idea that we can do something about it is hard to resist.
While I'm not pursuing longevity as doggedly as my friend Steve, I am certainly interested enough to get my telomeres measured.
The detailed workings of telomeres first came to light in the 1980s through the work of Elizabeth Blackburn, who won the Nobel Prize in medicine in 2009 together with Carol Greider and Jack Szostak. Dr. Blackburn is also a co-founder of Telome Health, which employs a method called QPCR to measure telomere length – a test which retails for about $400 a pop.
There are other testing methods, with a range of accuracy and costs, but they all work by zeroing in on the repeating sequence of nonsense DNA that can be found at the tips of every chromosome. The sequence serves the same purpose as a film leader. As cells divide, chromosomes naturally get shorter over time – telomeres offer protective buffering, so that in this process important information isn't sacrificed.
In time, advocates of testing say, telomeres will become a routine health diagnostic like cholesterol. For now, though, the easiest way to get your telomeres tested in Canada – outside of clinical research – is through a place like the Executive Health Centre, a Toronto clinic that offers preventive health care for its high-performing clients (and which offered me a free telomere test for the purpose of this story).
Elaine Chin, the chief medical officer of the centre, says about 30 of her clients have asked for a telomere test since she began offering it this year.
She stresses its value as a spur to behaviour modification. It's one thing to step on a scale and find out that being overweight is a risk factor for cardiovascular disease and diabetes. It's somehow a bit more jarring to put your DNA under the microscope and witness how your particular mode of living is playing out at a molecular level.
"People will not change their behaviour until they know they own a problem," Dr. Chin says.
Knowing whether or not I own a problem means rolling up my sleeve and giving up some blood – lots, in fact, 14 vials in all. The reason for the big draw, Dr. Chin explains, is that the centre is not promoting telomere testing in isolation but as part of a big picture health assessment that includes looking at a wide range of nutrients and other factors in my blood.
This makes me skeptical about whether knowing my telomere length is going to tell me anything truly meaningful apart from the common sense health message about eating right and exercising more. Yet, I'm also apprehensive that it will tell me something I really don't want to know.
What comforts me, paradoxically, is that despite media reports, telomeres do not actually tell you how long you are going to live. That's because there's a huge variation between individuals. A teenager can have shorter telomeres than a 70-year-old, yet that teenager is far more likely to still be around in 20 years. The correlation between telomere length and lifespan is something that emerges when larger numbers of individuals are analyzed as a group.
"It's not a crystal ball; it's statistical," said Dr. Blackburn at a recent appearance in Toronto organized by the Executive Health Centre.
What's more significant for individuals, proponents of the testing stress, is the rate of change in the length of our telomeres. That can be monitored year after year and used as an incentive to promote changes to diet and other habits.
Telomere length can also tell us about our risk of certain diseases. Short telomeres appear to correlate with higher risks for cancer, diabetes and cardiovascular disease. With telomere testing, individuals who come up short could be warned to take preventive steps, or to treat other risk factors such as stress and depression which may work in tandem with telomeres to shorten lifespan. For those who are already battling disease, the information could help guide treatment.
"Already in certain settings you can see that people who have short telomeres are responding poorly to certain drugs," Dr. Blackburn said.
As the population ages in much of the world, individuals and as well as nations face huge burdens associated with chronic disease. Any reliable indicator that can help reduce those burdens may be just what overtaxed health-care systems need most in the coming decades.
In that broader sense, telomeres are part of a larger move toward personalized (and preventive) medicine propelled by the increasing affordability of reading and interpreting human DNA. What is today the exclusive province of private clinics such as the Executive Health Centre may be the future of public health.
There is a catch
If most of human history can be characterized by its lack of information about individual health and the risk of disease, it's also the case that for people living in the developed world today it's possible to have the opposite problem. There are so many different kinds of diagnostic tests available it's become a meaningful question to ask just how much information is relevant to maintaining health, and how much is simply worrisome noise.
With the field still trying to figure out exactly how telomeres relate to aging and health, some researchers express strong reservations about telomere testing for health assessment – and taking tests at face value.
"It's easy to get correlations in aging, because many, many things are affected as you get older," says David Harrison, a gerontologist at the Jackson Laboratory in Bar Harbor, Me. While he doesn't rule out that telomeres play a role in aging, he is not persuaded that their role is clear or that telomere testing is meaningful. And he is wary, he says, when researchers in the field have a commercial interest in the testing technology.
Peter Lansdorp, a professor of medicine at the University of British Columbia and scientific director of the European Research Institute for the Biology of Ageing in the Netherlands, is also cautious about individual testing. He argues that the variation in telomere tests – the degree to which the same test performed on the same sample would lead to a different result – is still too high for a single test to be very meaningful.
On top of that, he says, a test provides only an average telomere length across all of a cell's chromosomes. It's not entirely clear that such an average is important, since it is the shortest telomeres that are more relevant to disease.
Dr. Blackburn herself is careful to say that the mechanisms that may connect telomeres and telomerase to disease are not yet worked out, but says that clear associations are showing up in the data. She is now involved in looking at the telomeres of some 100,000 individuals though the Kaiser Permanente Research Program on Genes, Environment and Health. Among the early findings, she says, is that the longer past 80 a subject lives, the more likely he or she is to have longer telomeres than most.
Other work shows that the give and take between tearing down and building up telomeres includes a strong link to cancer. Cancer cells divide uncontrollably and certain types of cancer are linked to an overzealous production of telomerase. One avenue for shutting down tumour cells may be through inhibiting telomerase.
This also leads to the most speculative and tantalizing aspect of telomere science: that by enhancing telomerase production in normal cells the negative effects of telomere shortening can be thwarted and average lifespan – or at least healthy lifespan – can be extended.
Or to put it another way: A drug that enhances telomerase may do the same or better than healthy living, allowing us to have our cake, literally, and eat it too.
Current research in this area has focused on a telomerase activator called TA-65 with intriguing results. In 2011, a group of researchers at the Spanish National Cancer Centre found that TA-65 extends telomeres in mice without increasing cancer risk.
Most would say it is far too soon to know whether such work will lead to a genuine breakthrough or whether telomerase activators will eventually become as common as vitamin pills. Maria Blasco, who co-authored the study at the Madrid centre and who is also the chief scientific adviser to Life Length, another company that makes telomere tests, says, "It is likely that the first pharmacological telomerase activators will be used to treat diseases associated with extreme telomere shortening."
Nevertheless, a cottage industry in telomere activation is already booming, mainly because TA-65 is a naturally occurring substance, extracted from Astragalus, a common herb. That means it is not regulated by the U.S. Food and Drug Administration, and so TA-65 can be ordered online.
Meanwhile, a couple weeks have passed and I'm back at the Executive Health Centre to get my results. To my pleasant surprise, I find my telomeres are slightly longer than average for someone my age.
My first thought is that I should thank my 91-year-old mother, who may have given me some good genetic armour that is counteracting all of my bad behaviour. My second thought is that this kind of anecdotal reasoning is precisely the sort of unscientific just-so story that is almost inevitable when one tries to explain a single point of data that is influenced by many hidden factors and may simply be random.
Dr. Chin says it's what I do with the information in my approach to personal health that matters. And maybe telomere testing, at least for the time being, is an invitation to a bit of self-deception in service of a greater good.
Certainly I've become more aware that there's an awesome and delicate machinery at work in every cell of my body. And even though I'm not entirely sure scientists know what it's doing, I have to admit I'm less inclined to eat a doughnut and gum up the works. If Steve is shooting for 150, maybe I can aim a little higher too.
Guilt by association?
A sampling of recent studies show correlations between telomere length, disease, longevity and health risk factors...
- Heart disease: A study of more than 3,500 patients with heart disease showed that telomere length is a predictor of survival rates. (Anderson, et al, Circulation, 2013)
- Dementia: In 1,983 subjects older than 65, shorter telomeres have been associated with the early onset of dementia. (Honig et al, Journal of the American Medical Association - Neurology, 2012).
- Depression: The measurement of 1,063 subjects in Scotland correlated shorter telomeres with a history of depression in younger adults. (Phillips et al, Psychosomatic Medicine, 2013)
...but not always
- Diabetes: A study of 3,968 women in the Nurse’s Health study found no strong correlation between telomere length and Type 2 diabetes. (Du et al, Public Library of Science One, 2013)
- Obesity: A study of 439 overweight or obese women found 12 months of dietary weight loss and exercise did not change telomere length. (Mason et al, Obesity, 2013)