Standing Up for Your Heart
You don't have to exercise to help your heart. Sure, exercise will probably make your heart last longer, but it's not the only thing you can do to avoid the biggest complication of diabetes.
Just standing up -- otherwise known as giving your butt a rest -- now seems to work independently of physical activity to reduce your chance of dying from heart disease. A 2010 study that the American Journal of Epidemiology published indicates that the less leisure time we spend sitting the better it is for our hearts.
The lead author, Alpa Patel, Ph.D., of the American Cancer Society's epidemiology research program, sent me the full-text of the study when I requested it. Dr. Patel and seven of her associates explored the connection between sitting and mortality by analyzing the survey responses of 123,216 people who had no history of cancer, heart attack, stroke, or emphysema, or other lung diseases. These were people who enrolled in the American Cancer Society's 1992 Cancer Prevention II study.
The researchers examined how much time those people sat down after work as well as how much exercise they got between 1993 and 2006. The results were clear. How much time they spent sitting was associated with an increased risk of death from heart disease for both men and women. Women (but not men) who sat less had a smaller risk of dying from cancer. Women who reported that they sat for more than six hours a day during their leisure time versus those who sat for fewer than three hours a day had a 37 percent higher death rate from all causes. For men it was about 18 percent higher.
"Prolonged time spent sitting, independent of physical activity, has been shown to have important metabolic consequences, and may influence things like triglycerides, high density lipoprotein (HDL), cholesterol, fasting plasma glucose, resting blood pressure, and leptin, which are biomarkers of obesity and cardiovascular and other chronic diseases."
After adjusting for the amount of physical activity these people got, the researchers found that the association remained virtually unchanged. But when people sat more and exercised less, the difference was even greater. Women had a 94 percent higher death rate from all causes. For men it was 48 percent higher. "Several factors could explain the positive association between time spent sitting and higher all-cause death rates," Dr. Patel says. "Prolonged time spent sitting, independent of physical activity, has been shown to have important metabolic consequences, and may influence things like triglycerides, high density lipoprotein (HDL), cholesterol, fasting plasma glucose, resting blood pressure, and leptin, which are biomarkers of obesity and cardiovascular and other chronic diseases."
This type of study is called a prospective cohort study. It follows over time a group of similar individuals who differ with respect to certain factors under study, in order to determine how these factors affect rates of a certain outcome. "The prospective study is important for research on the etiology of diseases and disorders in humans because for ethical reasons people cannot be deliberately exposed to suspected risk factors in controlled experiments." Prospective cohort studies are a useful type of observational study. One of my favorite bloggers, Dr. Michael Eades, makes that point forcibly in his post critiquing Dr. T. Colin Campbell's The China Study. "But in the end it is still only an observational study," Dr. Eades writes of The China Study. "Correlations are not causation. Any scientist worth his/her salt will tell you that all you can do with data from observational studies is use them to form hypotheses that can be rigorously tested in randomized, controlled trials."
So we should continue to look for proof that we will be more healthy if we sit less. As science progresses we may know that for sure in a generation or two. Meanwhile, the new study has already prompted me to stand up more. I already get a lot of exercise. I even get up from my desk chair or easy chair pretty often. I used to think it was unfortunate that I had to. I have what my late wife used to call "bitty buns." I have so little padding on my rear end that sitting down for more than a few minutes at a time gets uncomfortable even when I use seat cushions. I used to think that this was a problem. Now I am going further, following up on my renewed interest in converting my computer time from sitting to standing. Dr. James Levine, a Mayo Clinic endocrinologist, is my model. Four years ago I wrote here about how he mounted his computer over a treadmill, and while he works, he is walking at the rate of 0.7 miles per hour.
A few months ago I told Abhijeet Mhapsekar, who programs mendosa.com, about walking on a treadmill while he worked to help his bad back. My programmer actually did get a treadmill with his computer mounted over his desk. When Abhiheet was considering a treadmill desk, I told him that I wouldn't get one unless he did. Now the ball is in my court. And in yours.