Too Much Sitting Increases Mortality Risk

An opinion article by Professor Koichiro Oka of Waseda University, Japan

A sitting epidemic

Copyright : Waseda University
Copyright : Waseda University

Have you ever thought about how much time you spend sitting, from the time you wake up until the time you go to bed? Think about it—you sit when you watch TV, while you’re on the computer, working at your desk, during meetings, during your commute on a bus or train, while driving your car… what does it all add up to?

One of our studies found that Japanese adults between the ages of 40 and 64 spend an average of two and a half hours watching TV and about an hour on their computers or smartphones during their leisuretime, plus abut three hours at work and half an hour in their cars sitting each day. The total daily average came to eight or nine hours. An international comparative research study of average sitting times for adults across 20 countries1 found that Japanese adults sat the longest of all, suggesting that too many of us are sitting for far too long.

Figure 1 shows the results of assessing the percentage of time spent doing moderate to vigorous physical activity, light physical activity, and sedentary behavior among Japanese adults using an accelerometer. The moderate to vigorous physical activity that has been the focus of prior health promotion research makes up just 5% of the total waking hours, while the overwhelming majority of time is spent doing light physical activity (35–40%) or sedentary behavior (55–60%). It is obvious that human physical activity has been significantly curtailed as we spend our days in increasingly mechanized and automated living and working environments, thanks to a host of ongoing technological advances. There are concerns that we beginning to see a further epidemic of excessive sitting across all areas of daily life.

Health risks of too much sitting

I’d like to share with you some of the latest research on the health risks of too much sitting. One study looked at the effect of total daily sitting hours on all-cause mortality risk2 and found that compared to adults who sat for less than four hours a day, groups who sat 4–8 hours, 8–11 hours, and 11 hours or more each saw their mortality risk go up by an additional 11 percentage points—even if they were getting the amount of physical activity recommended by the World Health Organization. In addition, compared to adults who spent less than two hours a day sitting and watching television in their leisuretime, those who spent 2–4 hours and 4 or more hours doing so each saw their all-cause mortality risk increase by 11 percentage points as well—with the risk of death by coronary heart disease increasing by 18 percentage points for each group3. Another study estimated that each additional hour of time spent sitting and watching TV shortened average life expectancy by 22 minutes4, while still another found that the risk of death due to coronary heart disease was a staggering 82% higher for adult men who sat for an average of ten or more hours a day in their cars compared to those who spent less than four hours per week driving5. A recent study that reviewed this kind of research on the health risks of too much sitting6 indicated that even among those who were getting an appropriate amount of physical activity overall, prolonged sitting was a risk factor not only for mortality but also for being overweight or obese, weight gain, diabetes, some types of cancers, and coronary heart disease. Recent reports have shown deleterious effects in terms of cognitive functioning, depression, functional fitness, musculoskeletal pain (particularly in the lower back, neck, and shoulders), and more. It seems that finding some way to reduce the amount of time we spend sitting is the key to extending our healthy years.

How to eliminate too much sitting

Figuring out ways to begin alleviating our excessive sitting habits somewhat has become a topic of worldwide discussion in recent years. Workstations and standing desks that can easily be configured to accommodate different standing and seated work positions depending on the task or height of the person are a recommended strategy for reducing sitting time among the many people who spend their working hours at a desk. Figure 2 shows the research lab where the graduate students in my seminar course regularly work. Because the life of a researcher necessarily involves more time spent sitting, I introduced a workstation environment that allows students to stand as they work on the computers, read materials, and so on. The effectiveness of this kind of setup has been backed by prior research findings. For example, putting in workstations manufactured by a company called Ergotron reduced daily sitting time at work by about two hours, an effect which was not only maintained three months later, but also resulted in increased HDL (“good”) cholesterol levels among study participants7. Another study featuring similar workstations8 found that in addition to reducing sitting time by about an hour a day, participants experienced improved subjective health in terms of reduced lower back pain, neck pain, mood, and more.

For those who spend a long time sitting at home in front of the TV or computer, it is recommended that you stand up every thirty minutes or so or at least once every hour and move the body around a bit. Some effective strategies include foregoing the use of the remote control when changing channels, taking care of other tasks (tidying up or doing dishes, for example) while the TV is on, moving around or stretching during commercial breaks, and so on. It is these repeated small actions in our daily lives that will maintain and improve our mental and physical health for years to come.

WASEDA’S Health Study (WHS)

While the global spotlight is on the health problems associated with prolonged sitting, there still has not been enough research on the negative effects it has within the Japanese population in particular. To address this issue, Waseda University launched the “WASEDA’S Health Study” project, or WHS, with the intention of generating its own advanced research findings in this area and sharing them with the world. WHS is a collaborative project between the Faculty of Sports Sciences and the Alumni Association, with Waseda alumni as its main target. The main idea is to find the keys to their long, healthy life by focusing on lifestyle factors such as exercise, diet, and stress. Part of the research project involves determining time spent in sedentary behavior as well as sitting patterns through the use of accelerometers or questionnaires. By tracking the health status of participating Waseda alumni over an extended period of time, we plan to identify the relationship between the two. We’ll then make use of the results from the WHS project to support better health not only among our alumni, but throughout the country as well. As part of that process, we hope to offer suggestions that incorporate relevant measures and guidelines.