Is Sitting the New Smoking Habit?
01:10 - What: CNN
highlights of the story
As time spent in sedentary life increased, premature death from any cause also increased.
The negative effects of sitting did not decrease with age, gender, race, BMI, or even exercise habits.
Take a break from exercise every 30 minutes, experts say. Regardless of how much exercise you do, excessive sitting is a risk factor for premature death, anew studypublished Monday in the Annals of Internal Medicine.
There is a direct link between the time spent sitting and the risk of premature mortality from all causes, the researchers said, based on a study of nearly 8,000 adults. As total sitting time increases, so does the risk of premature death.
The good news: People who sat for less than 30 minutes at a time had the lowest risk of premature death.
„Sit less, move moreThe American Heart Association encourages us to do this. But this simplistic guideline isn't enough, said Keith Diaz, lead author of the new study and a research associate in Columbia University's Department of Medicine.
"That would be like telling someone to just 'work out' without saying how," Diaz wrote in an email.
The exercise guidelines are precise, he explained. For example, the US Centers for Disease Control and Prevention.recommend to adultsGet two hours and 30 minutes of moderate-intensity aerobic exercise every week, plus muscle-strengthening activity two or more days a week.
"We need similar guidelines for seating," Diaz said.
"We thought a more specific guideline might go something like this: 'For every 30 consecutive minutes of sitting, get up and move/walk at a brisk pace for five minutes to reduce the health risks of sedentary life,'" he said, adding The study "takes us one step closer to meeting these guidelines," but more research is needed to verify the results.
Getting older means sitting more
To understand the relationship between physical inactivity and premature death, Díaz and colleagues at Columbia, NewYork-Presbyterian/Weill Cornell Medical Center and other institutions looked for reasons for geographic and racial differences in stroke (REGARDS), a study sponsored by the National Institutes of Health.
"The REGARDS study was originally designed to investigate why black people (and especially black people in the southern US) are at greater risk of stroke than white people," Diaz said. He and his co-investigators followed 7,985 black and white adult participants aged 45 and older who had applied to the REGARDS project for an average of four years.
To measure the sedentary time of these adults, the research team used hip-mounted accelerometers. During the study period, the team recorded a total of 340 deaths, which were considered “all-cause mortality” — any death, regardless of cause.
Analyzing the data, the team found that sedentary behavior accounted for about 12.3 hours of an average 16-hour waking day, on average.
"As we age and our physical and mental function declines, we become increasingly sedentary," Díaz wrote.
Previous studies with adults have found that the average daily sitting time is only nine to ten hours a day. The higher mean in his own study is likely "due to the fact that we studied a middle-aged and older population," Díaz wrote. "It could also be partly because we use an activity tracker to track sedentary time, rather than using self-reports."
When measuring duration, the researchers measured participants who sat for an average of 11.4 minutes at a time.
Premature death from any cause also increased as the time spent sedentary increased, the results showed. The same was true for the longer seated stretches. Overall, participants' risk of death increased along with total sitting time and duration of seated stretching, regardless of age, gender, race, body mass index, or exercise habits.
"We found that there was no threshold or boundary where the risk of death increased dramatically," Diaz said, explaining that the risk of death increased as the sitting position increased. "To give you a specific number, those who sat more than 13 hours a day had a 2-fold (or 200%) increased risk of death compared to those who sat less than 11 hours a day."
"The length of the fight is a bit more complicated," Diaz said. Still, he said, the study results show that those who frequently sit in stretches for less than 30 minutes have a 55% lower risk of dying than people who typically sit for more than 30 minutes at a time.
After all, people who frequently sit for more than 90 minutes at a time are almost twice as likely to die as those who almost always sit for less than 90 minutes at a time, he said.
"Uncertain" underlying reasons
How sedentary behavior negatively affects our health is "unclear and complex," wrote Dr. David A. Alter, Associate Professor at the University of Toronto in Ontario, in aeditorialpublished with the study. Alter, who did not contribute to Diaz's research, said some scientists theorize that prolonged sitting decreases insulin sensitivity, while others believe net calorie expenditure decreases with increased sitting time.
The study was not designed to show why sitting increases the risk of premature death, noted Alter, who called the study "methodologically rigorous" and its results "robust."
He said arguably the study's most important contribution was to separate two sedentary behaviors: total daily sedentary time and uninterrupted sedentary duration.
"People with uninterrupted sedentary episodes of 30 minutes or more had the highest risk of death when their total sedentary time also exceeded 12.5 hours per day," Alter noted. "On the other hand, among those whose daily sitting volume was low, the duration of uninterrupted sitting had little or no associated effect on mortality."
By unraveling these two issues, the results show that too much sitting is bad, and worse when it builds into long, uninterrupted sessions throughout the day, Alter noted.
dr Suzanne Steinbaum, director of women's heart health at Lenox Hill Hospital in New York, said, "The longer we sit, the worse it gets. The longer we sit, the more negative the impact on our cardiovascular health."
Steinbaum, who was not involved in the study, said moving every 30 minutes is recommended.
"When we do this for the first time, the positive effects are immediately noticeable," he said. "We need to pay more attention to the movement."
Join the conversation
When asked if a standing desk might be useful for office workers, for example, Diaz said, "There is limited evidence that standing is a healthier alternative to sitting."
"So if you have a job or lifestyle that requires you to sit for a long time, the best suggestion I can make is to take an exercise break every half hour," Diaz said. "Our results suggest that this behavior change may reduce the risk of death."