Sitting Time Linked To Increased Heart Disease and Cancer Mortality

David Alter, MD, PhD FRCPC Senior Scientist Toronto Rehabilitation Institute-University Health Network and Institute for Clinical Evaluative Sciences Research Director, Cardiac Rehabilitation and Secondary Prevention Program Toronto Rehabilitation Interview with:
David Alter, MD, PhD FRCPC Senior Scientist

Toronto Rehabilitation Institute-University Health Network and Institute for Clinical Evaluative Sciences
Research Director, Cardiac Rehabilitation and Secondary Prevention Program Toronto Rehabilitation Institute


Medical Research: What is the background for this study? What are the main findings?

Dr. Alter: We knew going into the study that exercise was an important lifestyle factor that improved health. We also knew from studies that sedentary time was associated with deleterious health-effects. What we didn’t know was whether the health-outcome effects of sedentary time and exercise were really one and the same (i.e., albeit opposite ends of the same spectrum) or alternatively, whether the health effects of each were independent of one another.  We explored over 9000 published studies to quantify the health-outcome effects associated with sedentary behaviour and extracted only those which took into account both sedentary time and exercise. We found a consistent association between sedentary time and a host of health outcomes independent of exercise. Specifically, after controlling for an individual’s exercising behaviour, sitting-time was associated with a 15-20% higher risk of death, heart-disease, death from heart disease, cancer-incidence, and death from cancer. Sitting time was also independently  associated with a marked (i.e., 90% increase) in the risk for diabetes after controlling for exercise. In short, sedentary times and exercise are each independently associated with health outcomes. We hypothesize that the two may have different mechanism, and may require different therapeutic strategies. But, the health-outcome implications of both are each important in their own right.

Medical Research: What should clinicians and patients take away from your report?

Dr. Alter: A call to action. Several indeed:

First, from a public-health perspective, the signal between sedentary time and deleterious health-outcomes is one that is consistent for multiple diseases and health outcomes. Traditionally, public health and health promotion messaging has focused on exercise alone (among other healthy lifestyle behaviours like diet and smoking-cessation etc.). However, we believe that our study justifies the need for a modification in public-health and health promotion messaging – We must speak about the benefits of both “Exercise” and “Avoidance of excessive sitting” –  A two-pronged message – both are important, but distinct….  “An hour per day of exercise does not give the right of passage to sit for the remaining 23” – It’s time we incorporate the sedentary message into public health.

Second, while we need more scientifically-rigorous research on how best to decrease sitting times, there are things we can do as patients and health care providers in the meantime as the science of sitting times evolves. “Breaking cultural norms” is a challenge. However, we need to begin by providing greater specificity and granularity to our recommendations. The generic “sit less” “exercise more” is often lost on us. We know this already. What we often struggle with, however, is the “how”. While admittedly anecdotal, I’ve had success by setting out a step-by-step plan for my patients. I set forth tangible and achievable tasks that patients can follow which promote self-monitoring, goal-set, and feedback.

How do I do this for my patients?  I begin by having patients monitor their sleeping times, sitting times, and exercise times per day using either a simple app or log-book diary I provide to them. Generally, one week of monitoring serves as a starting point. This task does two things: It engages patients into monitoring their sitting time behaviours to draw awareness to the issue, and serves as baseline set of measures against which I compare when monitoring progress. .  Then, I have patients set a goal – “how many fewer minutes per day should you sit over the next week?” And, “how will you achieve this?”

Some practical tips? Begin by having the patient setting a timer at work to remind them on the half-hour, to get up and stretch from their sitting position and stroll for 2 minutes; There are a host of other activities…..For example, every commercial break on TV, do the same; watch the last 5-10 minutes of a show standing than sitting….great for sports….Have patients multitask during their leisure time. For example, I am currently typing this email while on my elliptical…spelling errors aside, it feels like a “healthy way to message” in more ways than one. Finally, I have patients return where I will provide them with feedback. What health benefits did they achieve over the last week or two by sitting less? This, in my experience, is VERY IMPORTANT.  What patients (and providers) don’t realize is how much can be achieved with just little changes. For example, we burn 2 times as many calories standing as we do sitting. For an average 70 kg male, that is an incremental difference of 70 Kcal/hour. Walking will burn even more than standing- Doing the math, you realize that you can burn quite a number of calories per day through these simple strategies. Cumulatively over a week, month, or year, the numbers add up.

There are many potential approaches when feeding back such  information – – the aim is for patients to internalize the health-benefits of this behaviour change.  There are all sorts of software apps and tools that can help… And more will undoubtedly emerge in the coming years.

The bottom line: reducing sitting time is a distinct priority from our 30-45 minutes per day requirement for moderate to vigorous exercise – -both need to be done. Both need to be promoted. Both should be thought of as “health hygiene”.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Alter: More research is needed. Indeed, we have barely scratched the surface here. This underscores another call to action – – that to our research community. First, our study demonstrated that the measurement of sitting times varied from study to study. Definitions were all over the map in the studies explored. Therefore, we need a more uniform and consistent definition so that we are “speaking the same language” when embarking on further research. Second, we need to better understand the mechanisms by which sedentary behaviours lead to poorer health, and how this differs from exercise and it’s health promoting attributes. Plausible mechanisms are needed to help build the credibility of the message – – especially for clinicians and scientists. Teasing out the mechanisms will also give way to new approaches and solutions.  So, we need to look “underneath the hood” and dig deeper into mechanisms. Third,  we need to better understand how best to “intervene” in order to change the sedentary behaviours of individuals and what effects if any, such therapeutic interventions have on health outcomes. Solutions need be integrative and interwoven within an individual’s 12 hour waking day period- – In so doing, we also need to find better and more innovative ways of quantifying the health-benefits of sitting-less – – These will not be as aesthetic as weight loss. Nor might they feel as intensive as exercise. We need to incorporate health metrics which connect with patients in a way that motivates them from pushing on and sustaining their reductions in sitting times – – after all, solutions may be quite simple and intuitive – but will they resonate with patients? Finally, our approach to solutions may differ from individual to individual  For example, our study suggested that the deleterious effects of sitting time were most pronounced among those who did not participate in any regular exercise. On the flip side, the adverse health effects of sitting may diminished in magnitude among those who do participate avidly in regular exercise. This suggests that our research priorities may necessitate a better understanding of the population – – who are the sedentary non-avid exercisers in the population? Do they need different approaches to their otherwise sedentary but avid-exercise counterparts?

In short, there is a lot more work to be done.  We are hoping that this study serves as a call to action for all!


Biswas A, Oh PI, Faulkner GE, Bajaj RR, Silver MA, Mitchell MS, et al. Sedentary Time and Its Association With Risk for Disease Incidence, Mortality, and Hospitalization in Adults: A Systematic Review and Meta-analysis. Ann Intern Med. 2015;162:123-132. doi:10.7326/M14-1651

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Last Updated on January 20, 2015 by Marie Benz MD FAAD