America Has a Sitting Problem – The Negative Health Effects of Being Sedentary
As discussed several times in the MGC blog, there are multiple, interacting lifestyle factors underlying the epidemic of chronic non-transmissible disease that has been unfolding in the US over the past 75 years. There is accumulating evidence that an unhealthy diet, exposure to environmental toxins, poor sleep quality, chronic stress and a compromised gut microbiome are all interacting to create low grade systemic immune activation in the gut and throughout the body, leading to metabolic dysregulation and chronic diseases affecting all organs, including the brain. In addition to these well-known factors, an extensive body of research strongly suggests, that dramatic changes in the pattern of our daily physical activities over the past 75 years, also play an important role in the increasing prevalence of these diseases. Most importantly, research shows that there are simple ways to counteract this negative influence.
In 1950, 10% of households in the United States owned at least one TV, whereas this number has increased to 98%, indirectly implying that more people are spending more time sitting in front of their TVs, rather than pursuing some physical activity. Sitting in the car while commuting to work for hours every day is the result of a steadily increasing percentage of the population living in suburbs (a number that has increased from 15% in the 1940s to 50% in 2000) rather than in the center of cities within walking distance of work and shops. A similar trend is observable in the workplace: In 1950, there were 16,000,000 workers in the United States who had sedentary jobs, whereas this number has increased almost 4-fold, to 58,000,000 or 42% of our current workforce.
The shocking news is that adults in the US spend nearly 80% of their waking hours in a sitting position, spend about 20% engaged in light intensity physical exercise, like walking, and only 1.5% in moderate to vigorous exercise like running or weight lifting.
We have known for a long time that physical activity is something that is healthy for us, and the popularity of gyms, particularly amongst younger individuals clearly reflect this increased awareness. However, amongst younger, healthy individuals, the trend to work out in gyms, go mountain biking and running has been fueled not so much by health considerations, but by a desire to look good, by keeping body weight down and increase muscle mass. What often gets unnoticed is the strong correlation between regular physical exercise and many aspects of our health.
Something that has received little attention is how big of a toll our increasingly sedentary lifestyle has inflicted on our overall health, and what role it plays in the unfolding chronic non-communicable disease epidemic. Evidence shows that sedentary behavior is associated with an increased risk for stroke, diabetes, high blood pressure and cancer mortality, the very diseases that make up the epidemic.
I recently attended a fascinating talk by Dr. Keith Diaz, a professor at the Center for Behavioral Cardiovascular Health at Columbia University Medical Center, who has published extensively on the detrimental role that our sedentary lifestyle plays in the current chronic disease epidemic and who has published simple guidelines to fight this unhealthy trend.
Looking at the risks conferred by sedentary behavior, Diaz et al. 2017 found that the risk for all-cause mortality by being sedentary, without moderate to vigorous physical activity (as you get working out in the gym for 90 min), was elevated only for those who were sedentary for greater than 11.5 hours per day. The study was a prospective cohort study looking at 7985 black and white adults aged 45 years and older. Those who were sedentary for 11.5 – 12.4 hours were 41% more likely to experience all-cause mortality. Those who sat in their chairs for 12.4 – 13.3 hours per day were 104% more likely, and those who were greater than 13.3 hours per day were 247% more likely to experience all-cause mortality.
When adjusting for moderate to vigorous physical activity, being sedentary for greater than 11.5 hours was still associated with an increased risk for all-cause mortality, with an increased risk of 163% for greater than 13.3 hours.
Now let’s look at if the issue here is total sedentary time or prolonged, uninterrupted sedentary time. In other words, does it make a difference if somebody is sitting on their desk all day without interruptions, as opposed to people interrupting their daily sedentary routine by getting up frequently from their desk. As shown in the figure above, one can see that those who were sedentary for shorter periods of time (left column, between 1 – 29 minutes), had no increased risk for all-cause mortality, for 30-59 minutes, the risk became slightly elevated (second column from left), and for anyone sitting for 60-89 minutes or greater than 90 minutes (right two columns), the risk became significantly higher.
Based on an extensive body of research, Diaz recommends a simple, individualized, and flexible lifestyle modification. The recommendations are broken down into two categories: moderate to vigorous exercise & interruption of sedentary time. The exercise component includes a recommendation of 3-5 days per week of moderate to vigorous aerobic exercise, like running, resistance training, and power yoga for a duration of 20 – 60 minutes. The other, equally important but often neglected, recommendation is the regular interruption of sedentary behavior with brief bouts of movement. The goal is to be sedentary for less than 9.5 hours per day, with movement of any intensity (more intense, the better) every 30 minutes for any duration (the longer, the better).
In summary, if you weren’t aware of these startling numbers, this information may make you want to reconsider your daily routine at work or during studies: introduce frequent interruptions into your schedule in the form of going up and down the stairs, walking around the block or just get up for a few minutes and stretch. If pursued on a regular basis in addition to your daily workout schedule, it may be as important for your health as eating a healthy diet and getting a good night’s sleep. Obviously, following all three of these lifestyle modifications gives you the maximal benefit.
E. Dylan Mayer is a graduate from the University of Colorado at Boulder with both a major in Neuroscience and minor in Business. He is fascinated by the interactions of brain, gut and microbiome, and the role of nutrition in influencing the health of our microbiome, as well as our own well-being. He is currently earning his Master’s Degree in Human Nutrition at Columbia University.