Does a standing desk lengthen your lifespan?

Standing desks are all the rage lately. These desks allow you to stand up while working on your computer. Some standing desks can be raised and lowered, so you can alternate during the course of the day between sitting and standing. The principal argument for these desks is that they provide health benefits.

Proponents of standing desks claim, plausibly, that they give you more energy and improve posture. The CDC has found that standing desks (or “sit-stand” desks) reduce upper back and neck pain and improve moods. At Smithsonian.com, Joseph Stromberg reported that standing desks reduce the risk of obesity and type 2 diabetes. And a 2012 Australian study found that prolonged sitting increased the risk of death. In other words, standing up more and sitting less can help you live longer. All this makes me want to stand up right now.

The newest claim is that standing up lengthens your telomeres. If true, this would provide a mechanism to explain how standing up might lengthen your life. The new study, led by Swedish scientist Per Sjögren, appeared this month in the British Journal of Sports Medicine.

Telomeres are special DNA “caps” on the ends of everyone’s chromosomes. As we age, these caps gradually get shorter, and if they get too short, the cell dies. They function as a kind of molecular clock, telling a cell when it’s old. A substantial body of scientific evidence shows that if you can maintain telomere length, cells—and their owners—will live longer.

But how could merely standing more, or sitting less, shorten our telomeres? Being skeptical, I read the paper.

Here’s what Sjögren and colleagues did: several years ago, they conducted a study measuring the effect of exercise on weight, cholesterol levels, and a few other characteristics. That study included 101 people, all 68 years old. They randomly chose 49 people (14 men, 35 women) to study the effect of exercise on telomere length. They used blood samples taken 6 months apart, both before and after the exercise regimen. This was all completed back in 2011.

Previously, they reported that there was no difference in telomere length between the “exercise” group and the control group. So how can they publish a new study that seems to reach the opposite conclusion? It turns out there isn't a new study at all, but a re-analysis of the original data.

In the early study, the exercise program did have some significant effects: it increased the amount that people walked around by 1663 steps per day, and decreased their sitting time by 2 hours per day. However, people in both groups spent less time sitting over the course of the study. So the scientists re-analyzed the data and looked at telomere length as a function of four more measurements. For one of these measures, change in sitting time per day, telomere length was reduced enough that the relationship showed a p-value of 0.02.

Unfortunately for Sjögren, this new finding is based on just 12 individuals. That's a tiny number for a scientific study. And when I looked at the key figure in the paper, it’s pretty clear that the effect depends critically on just 2 of those 12 individuals who had both reduced sitting time and longer telomeres. Take those 2 people out, and the effect vanishes. The authors admitted that

“The study sample is small and we cannot rule out that the findings are a chance phenomenon.”

We've seen this sort of thing before: a small study with a minimally significant effect. Usually these types of results never get replicated. As much as I’d love to believe I could lengthen my telomeres by standing up a bit more each day, this rather implausible findnig is simply unconvincing. It’s based on a sub-group of only 12 people—and furthermore, this is a re-analysis of previous data, which feels an awful lot like cherry-picking. If there is any effect, it’s very small.

Nevertheless, other studies do show health benefits from spending more time walking and less time sitting. A daily walk probably confers the same benefit as a standing desk, but a standing desk isn’t a terrible idea either. Just don’t count on it to lengthen your telomeres.

Should we test all women for breast cancer-causing mutations?

In this week’s Journal of the American Medical Association, famed geneticist Mary-Claire King argues that all women over age 30 should be tested for cancer-causing mutations in the BRCA1 and BRCA2 genes. King, who made the original discovery of the link between BRCA1 and breast cancer, is one of the world’s leading experts on how mutations in these genes cause cancer.

But her proposed new universal testing policy, which fellow Forbes contributor David Shaywitz calls “audacious,” goes far beyond what other experts recommend. Earlier this year, the highly regarded U.S. Preventative Services Task Force (USPSTF) recommended testing BRCA genes only in women with a family history of breast or ovarian cancer. 

Although there’s no question that King is an expert on BRCA gene testing, I think she’s gone much too far with her latest proposal. She has the science right, but she is far too optimistic about how her recommendation would actually play out. The policy might save some lives, but it would also cause a great deal of pain.

First, it’s worth explaining why King thinks universal BRCA testing is a good idea. In her JAMA article, King and colleagues describe a new study they conducted in Ashkenazy Jews that showed, somewhat surprisingly, that 

“50% of families found to harbor BRCA1 or BRCA2 mutations had no history of breast or ovarian cancer that would have triggered clinical attention." 

In other words, under current policy guidelines, 50% of people who have a damaging mutation in one of these genes will not have their genes tested. Many of them will eventually get breast or ovarian cancer—as King explains, women with harmful BRCA1 mutations have a 60% risk of cancer by age 60, and for BRCA2 the risk is 33% by age 60. That’s a very high risk, though it’s important to keep in mind that many women with these mutations will never get cancer.

With modern DNA sequencing technology, any large-scale genetic BRCA testing program is likely to uncover thousands of mutations that have no harmful effects, and thousands more whose effects are simply unknown. (Aside: each BRCA gene spans about 80-90 thousand nucleotides of DNA, and each of those letters can mutate in 4 ways, changing into one of the other 3 bases or just being deleted. This means there are at least 400,000 mutations possible in each gene, not counting larger deletions. A colleague and I published an article in 2010 describing one such BRCA test.) King is clearly aware that such reporting these mutations to patients would only sow confusion, and she recommends that:

“Testing for BRCA1 and BRCA2 should focus solely on unambiguously loss-of-function mutations with definitive effect on cancer risk…. A VUS [variant of unknown significance] can increase confusion and compromise clinical management; for population-based screening, these variants should not be reported.”

Herein lies one of the biggest problems with King’s idea. We don’t have universal agreement on which mutations have no significance, and even if we did, most physicians are not experts on cancer genetics. In our lawsuit-prone medical culture, there exists an unfortunate tendency to over-treat and over-report everything. 

Thus I fear that if we had wider BRCA testing, clinical labs would report all mutations back to physicians (how could they not?), and physicians in turn would report everything to the patients. The result would be that millions of women would be told "you have a mutation in BRCA1, and we don't know what it means." What's a patient supposed to do with that?

The other problem is that the only treatment to prevent breast and ovarian cancer is surgery to remove a woman’s breasts and ovaries. We don’t have a pill you can take, or lifestyle changes you can adopt, that will dramatically reduce your risk of hereditary cancer. But unlike a cancer diagnosis, the discovery of a BRCA mutation does not mean you have cancer. It simply means you have a risk, possibly a high risk, of getting cancer at a young age. We know from decades of research that people are not very good at evaluating risk. We tend to over-estimate the danger of events that seem very dramatic or visible to us, as cancer is to many people. 

By King’s own estimates, widespread BRCA testing would detect cancer-causing mutations in 250,000 to 415,000 women in the U.S. This estimate assumes the test doesn’t have false positives, which it almost certainly would. All of these women would then be faced with an extremely difficult dilemma: should they have both their breasts removed, or live the rest of their lives in fear of breast cancer? 

This dilemma was famously on display last year, when actress Angelina Jolie revealed in a New York Times article that she’d had a double mastectomy, after discovering that she carried high-risk BRCA mutations. Jolie’s mother died from cancer at the age of 56, and she explained in her article that as a result of the surgery, “ I can tell my children that they don’t need to fear they will lose me to breast cancer.”

King’s proposal is audacious, and it’s well worth debating. But without a better treatment option, telling hundreds of thousands of women that they have a high risk of breast and ovarian cancer carries a potentially enormous cost, both physical and emotional, for these women. Rather than putting huge numbers of women under the surgeon’s knife, we should instead double or triple our investments in research on treatments that may eventually make surgery unnecessary. 

Do high voltage power lines cause cancer?

This could be a very short article. I could just write “no, power lines don’t cause cancer"—but that wouldn't explain why so many people believe otherwise. And it won’t help people who are thinking about buying a home that has power lines nearby. So let’s look at this question a bit more closely.

For the past century or more, humans have been surrounding ourselves with an ever-growing array of electrical devices. All of these devices create electrical or magnetic fields, often called EMFs. There’s no doubt that our exposure to EMFs has increased dramatically in modern times. Not surprisingly, many people have worried that this is a bad thing. The belief is so pervasive that NIH has at least two websites devoted to this topic, one by NIEHS and one by NCI, as does the Medical College of Wisconsin. Realtors have created webpages to inform home buyers about how power lines might affect the value of their home. Not surprisingly, you can easily find companies on the Internet that will sell you devices (such as SafeSpace and EMFshield) to protect your body from the supposed perils of EMF.

People worry especially about high-voltage power lines, probably because they are carried by very large, highly visible structures that look vaguely threatening. This fear seems to have started with a 1979 study in which Nancy Wertheimer and Ed Leeper reported a correlation between high-voltage power lines and childhood leukemia in the area around Denver, Colorado. Wertheimer's results spurred numerous studies in the years since. A review of the evidence in 1995 pointed out that

“There is no known mechanism by which magnetic fields of the type generated by high voltage power lines can play a role in cancer development. Nevertheless, epidemiologic research has rather consistently found associations between residential magnetic field exposure and cancer.”

Scientifically, the question at the time was, were these associations real or coincidental?  If they were real, what’s the mechanism? Clearly, further studies were needed. Well, twenty years later, the data are in: power lines do not cause cancer.

In 2002, the WHO commissioned a huge (339 pages) and very thorough report on all the types of electrical and magnetic fields on the planet and how these EMFs might effect our health. Among its findings were:

“There is little experimental or theoretical evidence that mutations could be directly caused by ELF [extremely low frequency] magnetic fields…. There is little evidence that ELF electric or magnetic fields can cause malignant transformation of cells in culture.”

The final conclusion of the WHO commission was that

“Static electric and magnetic fields and extremely low-frequency electric fields are not classifiable as to their carcinogenicity to humans (Group 3).”

Group 3 means we don’t have any positive evidence that EMFs cause cancer. The only lower category, Group 4, would mean we have evidence that electromagnetic fields do NOT cause cancer, but such evidence is very difficult to produce. In other words, they concluded that the evidence didn't support a link, but more studies might yet find something.

After the 2002 report by the WHO, a study in 2005 raised the alarm again. In that study, Gerald Draper and colleagues claimed to find an association between the distance to the nearest high voltage power line and childhood leukemia. Draper found that living less than 200 meters from these power lines (in England and Wales) raised the risk of leukemia significantly compared to living at least 600 meters away.

The scientific reaction to the Draper study immediate and highly critical. Hepworth and colleagues pointed out that the results did not support a causal role for electromagnetic fields (which were not measured), but at best a geographic correlation. Kheifets and colleagues demonstrated out that the effect disappeared when the control groups were analyzed differently. Other critiques quickly emerged as well: a sign that science was working to self-correct, as it often does. But Draper’s study was widely reported, while the criticisms were not. The critiques, though, paint a compelling picture that Draper’s work was seriously flawed.

One of the most recent studies is from 2013 by Elliott et al. who looked at over 50,000 cases of cancer, including leukemia, brain cancer, breast cancer, skin cancer, and others. They found no increased risk for any of these cancer types and concluded

“Our results do not support an epidemiologic association of adult cancers with residential magnetic fields in proximity to high-voltage overhead power lines.”

This debate sounds very familiar. Many false hypotheses, such as the notion that vaccines cause autism, or that acupuncture can reduce pain, show the same pattern: a few small studies produce weak positive evidence, but then larger, better studies fail to back them up. Proponents always call for more studies, but if the effect is real, it doesn't disappear when you do a bigger study. If anything, the effect should appear stronger.

A major problem that the EMF alarmists have, which none of the proponents have ever answered, is one of mechanism: how is the very weak EMF from a power line supposed to cause cancer? Multiple theories have been suggested: maybe EMFs affect the movement of magnetic particles within cells, or alter the voltages across cell membranes—but as the editor of BMJ, Geoff Watts, put it in his response to the 2005 Draper study:

“Evidence to support these and other ideas is at best thin and at worst non-existent.”

So no, electrical power lines do not cause cancer. But they're still ugly. We should bury them all underground.