Patients Should Take a Break from Being Sedentary

Abstract & Commentary

By Rahul Gupta, MD, MPH, FACP, Clinical Assistant Professor, West Virginia University School of Medicine, Charleston, WV. Dr. Gupta reports no financial relationships relevant to this field of study.

Synopsis: Sedentary time is associated with an increased risk of diabetes, cardiovascular disease, and cardiovascular and all-cause mortality.

Source: Wilmot EG, et al. Sedentary time in adults and the association with diabetes, cardiovascular disease and death: Systematic review and meta-analysis. Diabetologia 2012;55:2895-2905.

In the United States, sedentary behavior has become animportant component of the obesity epidemic equation. Sedentary behavior is defined as any waking behavior associated with an energy expenditure ≤ 1.5 METs in a sitting or reclining posture. It is considered separate and distinct from a lack of moderate-to-vigorous intensity physical activity. In essence, too much sitting is now thought to be a health risk that is in addition to, and distinct from, too little exercise. Accumulating evidence suggests that more and more children, youth, and adults in the United States are spending excessive time being sedentary. While the explanation can be attributed to a host of reasons in our modern society, the resultant overweight and obesity and their associated health problems have a significant economic impact on the U.S. health care system. It is estimated that in 2008, the medical care costs of obesity alone totaled about $147 billion.1 Consequently, there is an increased interest in the health implications of excessive sedentary behavior. A recent meta-analysis revealed that prolonged television viewing was associated with increased risk of type 2 diabetes, cardiovascular disease, and all-cause mortality.2 While television viewing may be one of the most common causes of the “couch potato effect,” other sedentary behaviors, including desk work, screen time such as computers and video games, and reading, etc., must also be accounted for. As the body of epidemiological evidence on the adverse health outcomes associated with sedentary behavior continues to accumulate, it is important that we understand the full spectrum of the impact of sedentary behavior on chronic diseases as well as mortality.

In their research, Wilmot et al conducted a systematic review of the literature including various cross-sectional and prospective studies. A total of 18 studies were included with 794,577 participants. The results demonstrated that greater sedentary time (when compared with the least) was associated with a statistically significant 112% increase in relative risk of diabetes, 147% increase in relative risk of cardiovascular disease, 90% increase in relative risk of cardiovascular mortality, and 49% increase in relative risk of all-cause mortality. The statistical association between sedentary time and diabetes was found to be stronger than for mortality outcomes.

The researchers argued that there are a number of reasons for the strong association between sedentary time and diabetes. Peripheral insulin resistance is the hallmark for diabetes and impaired glucose tolerance. From research data in rodents, it seems that immobility quickly leads to significant peripheral resistance in skeletal muscle, which is the largest insulin-sensitive organ in the body. Similarly, human bed-rest studies also demonstrate that inactivity results in negative metabolic consequences, including insulin resistance.

Commentary

Despite the proven evidence of the health benefits of physical activity, the United States remains predominantly a sedentary society. Most of the primary care physicians have begun to routinely recommend physical activity to their patients at varying and appropriate levels. The chronic diseases and the resultant ensuing disability is often the reason patients give for not adhering to the recommended physical activity regimen. However, according to the CDC, new estimates reveal that nearly 26 million Americans have diabetes and 79 million have prediabetes. In fact, more than a third of all American adults are estimated to have metabolic syndrome. The above study is remarkable in this context since it attempts to distinguish the “too much sitting” from “too little exercise.” Research has demonstrated that interrupting periods of prolonged sitting, whether it’s at work or at home, can help in reducing insulin resistance, burning calories, and improving metabolic processes. A recent study from the National Cancer Institute comprising more than 650,000 individuals demonstrated that being active during leisure time (rather than sedentary) can add up to 4.5 years in life expectancy.3 Even moderate physical activity such as gardening and walking at a brisk pace lowered mortality when compared with no activity. Of interest in this study, in those who were both obese and inactive, the life expectancy was shortened by 7.2 years.

It is critical for the primary care physician to link this new and emerging evidence into an understanding that social and environmental determinants play an important role in the sedentary behavior of individuals, causing them to be overweight and obese. For those patients who are unable or unwilling to adhere to physical activity recommendations, it may be more important to address the sedentary behavior instead. So, the new paradigm would be for physicians to stress the fact that patients must not remain sedentary beyond 15 minutes or so without taking a break!

References

1. Finkelstein EA, et al. Annual medical spending attributable to obesity: Payer- and service-specific estimates. Health Affairs 2009;28:w822-w831.

2. Grøntved A, Hu FB. Television viewing and risk of type 2 diabetes, cardiovascular disease, and all-cause mortality: A meta-analysis. JAMA 2011;305:2448-2455.

3. Moore SC, et al. Leisure time physical activity of moderate to vigorous intensity and mortality: A large pooled cohort analysis. PLoS Med 2012;9:e1001335.