Sitting for long periods is associated with chronic disease and even early death. Yet researchers have little understanding of why this is true, even though the world is increasingly designed for sitting, according to a meta-analysis published today in the Annals of Internal Medicine.

Both the study and an accompanying editorial read like a call to arms for researchers in basic science and in the healthcare industry, as the cost implications of caring for an aging population saddled with the lifetime effects of sitting at desks and watching TV were clear in the data.

The authors, led by Aviroop Biswas, BSc, and Paul I Oh, MD, MSc, examined studies involving all-cause mortality, cardiovascular disease, diabetes, and cancer in adults by searching scientific databases for all studies published through August 2014. Forty-seven studies met the criteria, and meta-analyses were performed on 41. Data pooled from the studies found that after adjusting for levels of physical activity, prolonged periods of sitting were positively correlated with:

· All-cause mortality (hazard ratio [HR] 1.240, 95% confidence interval [CI] 1.09-1.41)

· Cardiovascular disease mortality (HR 1.179, 95% CI 1.106-1.257)

· Cardiovascular disease incidence (HR 1.143, 95% CI 1.002-1.729)

· Cancer mortality (HR 1.173, 95% CI 1.108-1.242)

· Cancer incidence (HR 1.130 95% CI 1.053-1.213)

· Type 2 diabetes mellitus (T2DM) (HR 1.910, 95% CI 1.642-2.222)

The editorial by Brigid M. Lynch, PhD, and Neville Owen, PhD, of the Baker IDI Heart and Diabetes Institute of Melbourne, Australia, calls the implications of the study “far-reaching.”

“Sedentary behavior is ubiquitous. Society is engineered, physically and socially, to be sitting-centric.”

Connections among sedentary behavior, chronic disease and their fallout in managed care have been researched before. In 2012, The American Journal of Managed Care reported results from Quinn, et al, which found overweight and obese men were less likely to undergo screenings for colorectal and prostate cancer, even though these men had diets lower in fruits and vegetables and were more likely to have sedentary lifestyles.

In the new edition of Annals, Drs Lynch and Owen draw connections between the findings and what they mean for governments that fund all or much of healthcare coverage, given how little is known about the science of how sitting affects cardiovascular activity. (They note, for example, that the Australian government recommends at least 5 hours of moderate physical activity each week.)

To address the weaknesses in research activity, they call for increases in 3 specific areas:

· Isotemporal substitution modeling. This examines the effects of different associations when time spent doing 1 activity is altered by another activity while time is constant.

· Objective activity montoring. At present, most activity is self-reported. Drs Lynch and Owen recommend using devices to track activity more precisely, such as whether the person was walking up an incline or suddenly accelerating, to reduce errors and provide a more complete picture of activity.

· Studies of population subgroups. Authors of the editorial note that limited information about subgroups is available, even though it is unlikely that risk levels are the same across the population.

Around the Web

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Sedentary Time and Its Association With Risk for Disease Incidence, Mortality and Hospitalization in Adults: A Systematic Review and Meta-Analysis

Too Much Sitting and Chronic Disease Risk: Steps to Move the Science Forward