Mind and Body
How Much Sitting Is Bad for Your Health? 10 Hours Is a Dangerous Maximum
Even if working out every day feels impossible, the fitness trackers of 36,383 adults provide a powerful reason not to give up on at least moving a little bit each day. New numbers published Wednesday in The BMJ show that any amount of activity — even activities that are so leisurely they may not even seem like exercise at all — go a long way toward holding death at bay.
The data in the paper, gleaned from eight studies, shows that 10 hours of sedentary time per day was associated with a 48 percent increase in risk of death. But even light exercise greatly reduced that risk.
Lead study author Ulf Ekelund, Ph.D., a professor of sports medicine at the Norwegian School of Sport Sciences, says this result shows that sedentary life and exercise are opposite sides of the same coin.
Specifically he found that around 300 minutes of light-intensity exercise (think: easy walking) per day could offset the risk of early death by as much as 50 percent. But that’s the maximum threshold. Ekelund tells Inverse that even if you don’t hit that threshold, there’s still a lot to gain from being moderately active.
"Every single step counts and reduces the risk."
“Having said that, for those who are inactive and do very small amounts of activity, every single step counts and reduces the risk,” says Ekelund. “Twenty-five minutes of brisk walking per day (which can be split up in shorter bouts) is associated with a substantially reduced risk for premature mortality.”
Ekelund and his colleagues’ key finding is actually measured in counts per minute (cpm), which is essentially how much movement a fitness tracker (or accelerometer, in the case of this study) picks up during the day. For example, a totally sedentary person would have a cpm of less than 100, since you still move around a little while seated, whereas someone doing light exercise would have between 101 and 1951 counts per minute.
In the paper, the authors note that 300 counts per minute was the maximum threshold for reducing risk of death. People who achieved that threshold reduced their risk by 66 percent.
But counts per minute can be hard to translate to real life, and in the paper, Ekelund’s team translates this data into something a bit more tangible: How many minutes of exercise you need to do to truly offset risk of death by the maximum amount.
For example, if you’re committed to doing light-intensity exercise (walking slowly, cooking, or dish-washing), 375 minutes was associated with a 52-percent decrease in risk of death compared to sedentary people. If you’re willing to work a bit more vigorously, 80 minutes of high-light (brisk walking) physical activity was associated with a 60 percent decrease in death risk. Finally, performing 24 minutes of moderate to vigorous exercise (jogging or carrying heavy loads) was associated with a 61 percent less likely to die.
Part of the value of Ekelund’s work is that it establishes a dose-dependent relationship between exercise and reducing risk of death. That’s important because when we think of exercise, we tend to think in thresholds: We aim for 10,000 steps per day, or we are told to hit 150 minutes of moderate activity by government guidelines. What these thresholds ignore is that even if you fall short of these cutoffs, you’re still benefitting from that exercise.
But for those enticed by the idea of hitting maximum risk reduction, Ekelund adds this “maximum” level of risk reduction is more attainable than it seems.
That average of 300 counts per minute of an accelerometer per day was “almost exactly the activity levels of US men,” based on analyses done in other studies — though it was 10-15 percent higher than that achieved by US women. In Norway and Sweden however, people are already crushing this metric, moving about about 10-15 percent more than that threshold.
Notably, none of these levels of physical activity require intense training. They just involve being moderately active — and if you want to be more time-efficient, they involve going on a jog that lasts less than 30 minutes. To get started, Ekelund says that it’s not necessary to shell out additional cash for workout gear or a class.
“Walking is an excellent type of physical activity. Simple, affordable (free) and achievable for the vast majority,” he says.
It may not be enough to make a successful athletic training plan, but even this basic amount of exercise can go a long way for most people’s health.
**Data Extraction and Analysis: Guidelines for meta-analyses and systematic reviews for observational studies and PRISMA guidelines were followed. Two authors independently screened the titles and abstracts. One author performed a full text review and another extracted the data. Two authors independently assessed the risk of bias. Individual level participant data were harmonised and analysed at study level. Data on physical activity were categorised by quarters at study level, and study specific associations with all cause mortality were analysed using Cox proportional hazards regression analyses. Study specific results were summarised using random effects meta-analysis.
Main Outcome Measure: All cause mortality.
Results: 39 studies were retrieved for full text review; 10 were eligible for inclusion, three were excluded owing to harmonisation challenges (eg, wrist placement of the accelerometer), and one study did not participate. Two additional studies with unpublished mortality data were also included. Thus, individual level data from eight studies (n=36383; mean age 62.6 years; 72.8% women), with median follow-up of 5.8 years (range 3.0-14.5 years) and 2149 (5.9%) deaths were analysed. Any physical activity, regardless of intensity, was associated with lower risk of mortality, with a non-linear dose-response. Hazards ratios for mortality were 1.00 (referent) in the first quarter (least active), 0.48 (95% confidence interval 0.43 to 0.54) in the second quarter, 0.34 (0.26 to 0.45) in the third quarter, and 0.27 (0.23 to 0.32) in the fourth quarter (most active). Corresponding hazards ratios for light physical activity were 1.00, 0.60 (0.54 to 0.68), 0.44 (0.38 to 0.51), and 0.38 (0.28 to 0.51), and for . moderate-to-vigorous physical activity were 1.00, 0.64 (0.55 to 0.74), 0.55 (0.40 to 0.74), and 0.52 (0.43 to 0.61). For sedentary time, hazards ratios were 1.00 (referent; least sedentary), 1.28 (1.09 to 1.51), 1.71 (1.36 to 2.15), and 2.63 (1.94 to 3.56).
Conclusion: Higher levels of total physical activity, at any intensity, and less time spent sedentary, are associated with substantially reduced risk for premature mortality, with evidence of a non-linear dose-response pattern in middle aged and older adults.