If you’re reading this headline at your desk, I’m sorry to share some bad news: a recent study in the Annals of Internal Medicine found that adults who are inactive for longs periods of time during the day are at risk for early death–even if they exercise regularly. As one researcher put it, “Sitting really is the new smoking.” The prospective cohort study, funded by the National Institutes of Health, followed nearly 8,000 adults in the United States aged 45 and over for a period of 4 years after recording their sedentary time in a one-week period using a hip-mounted accelerometer (as opposed to prior studies that relied on self-reporting to evaluate the total amount of sedentary time). The researchers found that both the total volume of sedentary time and its accrual in prolonged, uninterrupted bouts were associated with all-cause mortality. Accordingly, they suggest that physical activity guidelines target reducing and interrupting sedentary time to reduce the risk for death.
So what does this mean? Unfortunately, according to lead study author Keith Diaz of the Center for Behavioral Cardiovascular Health at Columbia University Medical Center in New York, exercise in and of itself is not enough. According to Diaz, the “findings suggest that it is simply not enough to be active or move at just one specific time of the day, that is, exercise . . . We need to be mindful of moving frequently throughout the day in addition to exercising.” Diaz noted that there should be specific guidelines for sitting, such as “for every 30 consecutive minutes of sitting, stand up and move/walk for five minutes at brisk pace to reduce the health risks from sitting.” Along these lines, the study found that people are less likely to die young if they break up sedentary time by moving around every half hour than if they remain seated for longer stretches of time without getting up. This would mean taking frequent “activity” breaks, since the study found that sedentary behavior, on average, accounted for about 12.3 hours of an average 16-hour waking day.
Some other interesting findings from an analysis of the data in the study: those who sat for more than 13 hours per day had a 2-fold (or 200%) greater risk of death compared to those who sat for less than about 11 hours per day; those who frequently sat in stretches less than 30 minutes had a 55% lower risk of death compared to people who usually sat for more than 30 minutes at a stretch; and people who frequently sat for more than 90 minutes at a stretch had a nearly two-fold greater risk of death than those who almost always sat for less than 90 minutes at a stretch.
The study is not without certain limitations. For one thing, the participants may not be representative of the general U.S. population. In addition, the accelerometers could not distinguish between sedentary time from sitting versus inactive periods when people were standing. And, the study was not a controlled experiment designed to establish how or whether sedentary time directly causes premature death.
Notwithstanding these limitations, the study does provide a cautionary tale for employers and their employees who spend large amounts of uninterrupted time sitting behind a desk. Employers may be wise to encourage employees to take more frequent activity or walking breaks and caution against remaining sedentary for long periods of time (e.g., for more than 30 minutes at a time). They may also consider providing employees with office furniture that encourages movement, such as treadmill desks, under desk steppers, or cycles. Unfortunately, despite their growing popularity, Diaz notes that “standing desks” may not be a solution: “there is limited evidence to suggest that standing is a healthier alternative to sitting.”