Over the last few years I’ve seen a great amount of fuss being made over the use of standing desks based on reports claiming that too much time spent sitting will kill you. The idea, at least from a health standpoint, that if you have a desk job, you’re better off standing at your desk all day rather than sitting. Doesn’t this new evidence contradict what we’ve always heard about the supposed health hazards present in jobs where standing all day is a requirement? If we were to look at the average lifespan of an assembly line worker, do they live longer lives than the average population, provided they have not been exposed to other obvious work-place hazards such as asbestos? I’m not even sure I can name someone I’ve met, myself included, who has had to stand all day at their job and didn’t wish they had a job where they could be sitting more often – because standing all day is painful. Who knew…
It seems that a lot of people do, in fact, know that being on their feet for prolonged periods of time is painful. Do a Google search for “jobs that require being on your feet all day” and you’ll see links several pages deep leading to discussions about the pains associated with standing and how to cope with it. Hidden among them you might see a couple articles that praise the health benefits of standing. Some of the common issues I see people having in these discussions range from feet and back pain, to poor circulation increasing the risk of carotid atherosclerosis and development of varicose veins. If you delve into the discussions people are having about standing desks, you may see stories about people who have tried it and eventually reverted back to a sitting desk. Then, of course, you have others who love their standing desks. They might say the folks who have tried standing and failed were not doing it right. They should have modified their set up with an ergonomic so and so, or should have used a padded mat to stand on, or special shoes rather than a treadmill. If standing for prolonged periods of time were so natural, then why should it require such specialized equipment?
One of the studies repeatedly cited by places like the NY Times that support the health claims for standing over sitting comes from the journal Diabetologia. This study reviewed data from 16 prospective studies and found that more time sitting was associated with an increased risk of diabetes, cardiovascular disease, and all-cause mortality. A few things that should be noted; all studies used self-reporting as a measure of time sitting and time sitting was defined by time spent participating on a particular activity associated with sitting – TV viewing time was the activity measured in almost all cases, and body weight, dietary and other lifestyle factors were accounted for in some of the studies but not all of them.
First of all, I’ve said it on this blog before but causation does not equal correlation. Epidemiological studies like these are inherently prone to error because its nearly impossible to isolate a single causal relationship due to the scale and uncontrolled nature of the studies. With that in mind, the only statistically significant correlation this study found was between greater sitting time (i.e. TV viewing time) and an increased risk of diabetes. Type II diabetes is known to be more prevalent in people who lead sedentary lives, so of course, there is going to be a greater association between sitting time and diabetes. Let’s not forget that diet, genetics, and activity level all come together as risk factors for diabetes.
One of the more well designed studies used in this review looked at 240,819 American men and women and found that 6.6%, or 15,942 of those reported having diabetes after an 8 year follow up with a self reported amount of TV viewing time greater than or equal to 7 hours per day. The study controlled for some of the biggest confounding factors such as age, diet and smoking. If you’re curious like me about the prevalence of diabetes in the overall population the National Diabetes Statistics in 2010 reports that 11.3% of Americans over the age of 20 are diabetic. That means if I did my own study and randomly sampled 240,819 American men and women, I would find that roughly 27,213 of them would have diabetes. If I eliminate the 18.1% of Americans who smoke I’m left with approximately 22,287 people with diabetes in my study, or 9% of the population. If I remove even more based on dietary factors its going to bring me closer to the 6.6% of the people found in the original study. Now, I can state in my report that this subset of people were at a greater risk of having diabetes due to sitting because they told me they watched more than 7 hours of TV a day, while ignoring other important factors like genetic predisposition and obesity.
In other words, how meaningful are the conclusions about sitting and diabetes when I can pull nearly the same numbers randomly out of the population without controlling for anything other than age and smoking status? Apply the same logic to the other risk factors derived from sitting and I’m willing to bet you’d come to the same conclusions. The study in Diabetologia found an overall increased risk of 49% in all cause mortality with sitting. I can also flip a coin any number of times and come up tails around 50% of the time.
Going back to my original thought about jobs that require standing for long periods of time, what are some of these jobs? Besides the assembly line worker, there is the postal service, retail, construction, food service and health care professions like doctors and nurses. All of these are high stress jobs that most people probably would not associate with longevity. In fact, there is a lot of documentation already out there that I will simply link to rather than repeat here that discusses the known health problems associated with occupations that require prolonged standing.
Common sense should prevail in these discussions. If you have the luxury of choice and stand rather than sit at your job, you’re probably healthier because you’re probably more health conscious in other parts of your life. You will burn more calories and exert more effort in standing if nothing else. And you’re probably going to be stressed out, depressed along with the physical factors that result from standing or sitting all day if you’ve got little choice in the matter. Reports that draw these very loose correlations to activities like sitting certainly do not merit extreme changes in lifestyle. If your job allows you the freedom to do so, I would think the best response would be a combination of sitting and standing throughout the day, rather than favoring the extreme.
Feel free to sit down and relax though, its not going to kill you.