By Robert Glatter, MD
If you sit all day at work, you may want to pay attention to recent research which demonstrates that prolonged sitting at work raises the risk of dying from cardiac and metabolic diseases, as well as the risk of dying from all causes, even if you work out or exercise.
More recent research is focusing on how sedentary behavior–including sitting and lying down– serve as behavioral risk factors for obesity and chronic disease. As employees spend 9 hours a day or longer at work, with fewer than 20% of jobs involving physical exertion at some level, (with many people spending at least 4 hours a day sitting at work), sedentary time at work is high, leading to dangerous circumstances for the many people affected.
In the study at hand, Anne Grunseit, PhD, from the Prevention Research Collaboration in the School of Public Health at the University of Sydney, Australia, and Norwegian colleagues investigated the relationship between occupational sitting, body mass index (BMI), and mortality in a general population sample from 1995-1997 (45,259). They evaluated 20 year old patients from Norway, placing patients into the following categories: mostly sitting, much walking at work, much walking or lifting, and heavy physical labor. Patients self-reported their level of sitting at work. They were stratified by BMI (healthy, 18.5 to <25 kg/m2; overweight, 25 to <30 kg/m2; and obese, 30 kg/m2 or greater). About 30% of participants reported having an occupation in which they were mostly sitting.
All-cause mortality increased as BMI increased from normal weight to overweight to obese (5.0, 6.8, and 9.4 deaths/1000 person-years, respectively). The trend was similar for CV/metabolic disease mortality (1.8, 2.8, and 4.4 deaths/1000 person-years, respectively). After adjusting for BMI and other variables (light and hard exercise, education, sex, general health, smoking status, and cardiac disease), sedentary work was associated with higher all-cause mortality and cardiac/metabolic disease mortality compared with occupations with significant walking, significant walking or lifting, or heavy physical labor.
Based on the study, all-cause mortality risk increased along with BMI for all levels of occupational activity. For employees with a healthy BMI, the mortality curves over time were the same for all levels of activity, but separated according to activity level as BMI increased, with the greatest risk for sedentary workers in the obese range. As an example, someone who has an active occupation (involving walking and lifting) had a 27% lower chance of dying than someone who mostly sat in their occupation among those in the obese category. Cardiovascular mortality risk was about one-third lower among overweight participants and 45% lower among obese participants who had walking and lifting occupations compared with sitting.
The author concludes that those in occupations involving some activity have lower rates for all-cause and cardiovascular or metabolic disease mortality, even when adjusted for demographic, health, and physical activity characteristics outside of work The study further demonstrated that the protective effect of occupational activity appeared to be significant for the groups whose BMIs were in the overweight or obese categories.
One limitation of the study is that it did not include a category for standing, and did not adjust for quality of diet. Strengths of the study included its prospective and large general population and long follow-up time (12-14 years).
The take home points from this study:
1. Reduced sitting at work would benefit overweight or obese people the most because they already have a higher baseline risk for mortality.
2. People would likely benefit from spending more time standing at work.
3. Using a “medicine ball” as opposed to a chair may be beneficial to engage core muscles if you must sit at work.
4. If you do spend a fair amount of time sitting at work, take frequent breaks to stand. Added tone from standing will allow your muscles to expend energy.