Q&A with 2017 Mustard Post-Doctoral Fellow on his recent and new research on prolonged sitting
The health risk of sitting too long has become a topic of great interest in recent years. In the workplace setting, it’s now increasingly common to see programs that use standing desks or time-tracking devices to encourage office workers to sit less. All the while, questions remain about what the evidence has to say about the effectiveness of strategies to reduce sitting time.
A new researcher at the Institute for Work & Health (IWH) hopes to answer some of these questions. Dr. Aviroop Biswas, who joined the Institute this spring as the 2017 Mustard Post-Doctoral Fellow, helped uncover the extent to which sedentary lifestyles are associated with health risks. A meta-analysis that he published in the Annals of Internal Medicine in 2015 (doi: 10.7326/M14-1651) was named one of the most influential articles that year by the American Heart Association’s Council on Lifestyle and Cardiometabolic Health. He shares what he has learned and where his research takes him next in this Q&A.
Q: You published a meta-analysis a couple of years ago that generated quite a lot of media coverage. Can you explain what you set out to find in this paper?
A: When we began this research, the knowledge at the time was that sitting for long periods was associated with a lot of health risks. But there was nothing that really consolidated the literature to quantify the independent association between prolonged sedentary time and health outcomes.
Our paper was the first meta-analysis to focus on the association between sedentary time and health outcomes, while adjusting for the effects of physical activity. What made our study unique was that we looked at the risk for two groups of people. One group was the “active couch potatoes”— people who exercised and met their recommended 150 minutes of moderate-intensity physical activity a week, but otherwise sat a lot for the rest of the day. The other group was people who didn’t exercise enough and were very sedentary.
Q: What did you find?
A: When we adjusted for the effects of physical activity across all the papers looking at adult populations, we found that prolonged sedentary time was associated with a 91 per cent increased risk for Type 2 diabetes. We saw increased risks for mortality from all causes, for cardiovascular diseases, for deaths from cardiovascular diseases. We also saw increased risks for both incidence of, and deaths from, certain types of cancer—particularly those associated with reproductive and metabolic health.
The higher risks I’ve just mentioned were found when comparing people who sat the most in a day with those who sat the least. We used that method because the studies in the review all defined their study groups and comparison groups differently.
To also understand how exercise affected these risks, we compared the highly sedentary people who didn’t exercise enough and the people who were highly sedentary but who also exercised. As I mentioned, this second group of people also sat many hours in the office or in front of the TV, but they also met the exercise guidelines of 150 minutes of moderate-intensity exercise a week. For this group, the risk for mortality from all causes was 30 per cent lower than for those who didn’t exercise enough. This suggested that exercise seems to have protective benefits.
Setting the record straight
Dr. Avi Biswas’s article in the Annals of Internal Medicine on the health effects of prolonged sitting generated quite a lot of media attention. Unfortunately, some of the coverage misrepresented the findings.
With headlines such as, “Excessive sitting is deadly, even with regular exercise, Toronto researchers say” or “Even with exercise, excessive sitting linked to premature death,” a number of articles gave the impression that physical activity has no benefit. However, Biswas’s meta-analysis did find protective effects of exercise.
In summary, the research team found:
- Prolonged sitting was linked to a 91 per cent increase in risk of Type 2 diabetes.
- Prolonged sitting was also linked with 15 per cent higher risks of cardiovascular diseases and associated deaths.
- It was also linked to 13 per cent higher risks of cancer and cancer deaths—specifically cancers of the breast, colon, uterus lining and ovarian epithelial cells.
- From the studies that looked at the relationship between physical activity and sedentary time on deaths from all causes, people who were highly sedentary faced a 46 per cent higher risk of dying early compared to people who were not sedentary.
- Those same studies showed people who were highly sedentary but who otherwise met the exercise guidelines of 150 minutes a week had a 30 per cent lower risk of dying than people who didn’t exercise enough.
Q: What might explain this link?
A: We’re still at the early stages of understanding this, so by no means is this the definitive answer. But one main hypothesis among researchers is that a sedentary lifestyle makes our body’s metabolic system less efficient. Sitting for long periods means that we use less of our skeletal muscles associated with our posture. The associated metabolic pathways, which are linked to the firing of our skeletal muscles helping us to regulate blood sugar, store fat and so on, aren’t as active and so the pathways become less efficient.
So what do you do? You would want to keep those muscles firing as much as possible by breaking up your sitting time. Breaking up your sitting boosts your metabolic system. Take standing breaks, walking breaks, and move around as much as you can.
Q: Where is there still debate among researchers?
A: There’s a big debate on what people should do to reduce the risks of a sedentary lifestyle. While some researchers recommend breaking up sitting with standing or light movement, another study I conducted found that intensity makes a difference. Calisthenics and walking around the office for a few minutes every hour seem to give a greater metabolic boost over a shorter period of time than just using a standing desk for long periods. Exercising regularly seems to give the biggest boost, and might even completely reduce the risks of sedentary behaviour if you do enough of it. Hence, some researchers (me included) still believe that any recommendation should focus on promoting regular exercise first.
Q: Where is your research taking you next?
A: My doctoral research focused on strategies to reduce sedentary behaviour for patients undergoing lifestyle-based rehabilitation after a cardiac event. During that time I found that people commonly spend a lot of their day at work, and work is where they do most of their sitting. Addressing the dearth of recommendations to reduce sitting at work is something I’m very interested in. I’m also looking to explore the intersection between the workplace environment, worker lifestyles and the prevention of illness and injury.
Q: What was it like to see so much media coverage for your research?
A: It was a very pleasant surprise, especially as it happened during my graduate studies. Not all the coverage was entirely reflective of our findings, however. Several media sources reported that the risks from sitting are great no matter how much exercise we do. I believe they misinterpreted our independent analysis of the effects of prolonged sedentary behaviour. Instead, the message should have been more optimistic—that regular exercise has protective benefits over the risks from sitting. Examples such as these made me realize the importance of clearly communicating research findings to the public.
Source: At Work, Issue 88, Spring 2017: Institute for Work & Health, Toronto
- "Too much standing hurts, too" (At Work article)