The study followed some 5000 men and women over a 16 year period and found that sitting at work or at home was not associated with increased risk of death even when age, socioeconomic status, ethnicity, health, alcohol consumption and diet were taken into consideration. So, according to these authors, sitting may not be as bad for us as we previously thought.
There remains little doubt that lack of exercise and a sedentary lifestyle represent key health problems in today’s modern society. A quick search on the World Health Organisation’s (WHO) website and you’ll find that physical inactivity ranks 4th in the global leading risk factors for mortality, with many countries around the world demonstrating a trend for women to be less active than men. While health organisations around the world are making a concerted effort to encourage the general public to incorporate exercise into their leisure and free time, this may not be the only period of our day that is dominated by sedentary behavior. Work forms one of the largest segments of sedentary time for employed individuals, and current trends have shifted parts of the working population into less active, ‘sitting’ jobs.
But what does this mean for our long-term health? One study, published last month in PLoS ONE, aimed to answer this question by assessing the impact of occupational sitting on the risk of cancer, cardiovascular disease, and all-cause mortality from a large number of British men and women. Stamatakis and colleagues gathered data from identical health surveys conducted in England and Scotland between 1994 and 2004. Subjects (5380 women, 5788 men) were classified based on whether the majority of time in their job was spent walking, standing or sitting. Subjects were further categorized on levels of physical activity during free time, alcohol intake, smoking, socioeconomic status, and whether they had cardiovascular disease or cancer at the time of the survey. The mortality rate (number of deaths) was then monitored over a 13 year follow-up period.
The major findings reported by this study were that standing/walking occupations carried a lower risk of mortality from either all-causes or cancer, in women but not men. When the researchers further compared groups based on free-time physical activity levels, they found that in both men and women, high levels of free-time physical activity coupled with a standing/walking occupation was associated with a lower risk of cancer and all-cause mortality versus low free-time activity coupled with sitting occupation. At first glance, it could be easy to take the results at face value, but there are limitations to the study design which the authors themselves highlight: Much of the data is self-reported, which may introduce bias, especially when it comes to levels of physical activity during free-time. In addition, there was no information available on how long individuals had been in their current jobs, nor was there any data for people switching jobs during the 13 year follow-up, which may have eventually placed them into a different category. The findings are also surprising given that a similar study published earlier in the year, found that even moderate free-time exercise was enough to reduce the risk of both cardiovascular and all-cause mortality, regardless of levels of physical activity in work.
The issue still seems unresolved, and it has also been discussed here on the blog earlier. Current exercise recommendations from the Norwegian Directorate of Health suggest daily physical activity levels should be at least 30 min, a total 3.5 hours per week, which has been shown in a number of studies to confer significant benefits to health and an overall decrease in mortality rates. However, a busy lifestyle, coupled with raising a family may make this target difficult to reach during our leisure time, making activity levels at work a significant factor in overall health. Everything is better than nothing, and maintaining a physically active lifestyle outside of work hours will contribute significantly to achieve the health benefits of exercise. However, if you’re still worried and have been sat at your desk for the last few hours, when you reach the end of this sentence, why not stand up and take a walk?
Allen Kelly, post doc at CERG.
Our previous blog post called for more than the recommended 30 minutes of daily exercise for people with inactive jobs or inactive lifestyles. Our campaign against inactivity goes on, today representing a study by an Australian research group. The findings concluded that each hour you spend sitting in front of the TV reduces your life expectancy by 21.8 minutes – ten minutes longer than a cigarette.
The study, lead by J. Veerman at the University of Queensland, was published in The British Journal of Sports Medicine. Data from 12000 Australians was collected by a national survey on diabetes, obesity and lifestyle. The respondents answered questions about health, diseases, exercise, smoking, dietary habits and hours of watching television per day.The goal was not to measure time in front of the screen specifically, but get a ballpark figure of the amount of hours a person spent sitting. With these data in hand, the researchers tried to isolate the factor of risk posed by long stay seated for other unhealthy habits like smoking and not exercising. Their conclusion was that adults who spends six hours a day sitting in front of TV, lives nearly five years less than persons who do not watch television.
Interestingly, another study on the same subject was published this fall by a British group in the scientific journal Diabetologia, and reviewed 18 studies – total 794,577 individuals investigated – that took into account not only the period in which the person remains seated in front of the TV, but also the time sitting at work. The authors showed that adults on average spend between 50 and 70 % of their day sitting. Furthermore, the study showed that people who spend more than seven hours a day sitting have a 112 % increase in risk of developing diabetes, 147 % in risk of cardiovascular disease and 49 % in risk of dying prematurely even if they exercise regularly.
So, the take home message is: spend less and less time sitting and exercise more! It’s just as simple as that. We will write more about this topic the coming weeks, and you can also find tips for exercising in previous blog posts.
Written by Gustavo da Silva, researcher at CERG.