Monday, October 22, 2012

Office chairs of death

Two recent studies remind us of the perils of sitting for prolonged periods. The big surprise here is that whilst exercise helps provide a measure of offset, prolonged sitting appears to be a bad thing in and of itself. If the conclusions are valid, they would suggest that the standard advice of exercising 3-4 times a week (with some gusto) is insufficient and we need to move about more while at work. Quite literally, an "uprising" may be called for.

Study 1: Published in Diabetologia:

  • "Sedentary time in adults and the association with diabetes, cardiovascular disease and death: systematic review and meta-analysis"
  • Analysed 18 existing studies involving almost 800,000 people.
  • Comment from the researchers: "Dr Emma Wilmot, who led the study, said it was clear that those who sat the most had a higher risk of diabetes, heart disease and death than those who sat the least.She said: "If a worker sits at their desk all day then goes to the gym, while their colleague heads home to watch TV, then the gym-goer will have better health outcomes."But there is still a health risk because of the amount of sitting they do. "Comparatively, the risk for a waiter who is on their feet all day is going to be a lot lower." She added: "People convince themselves they are living a healthy lifestyle, doing their 30 minutes of exercise a day. "But they need to think about the other 23.5 hours." BBC.

The hazards of high levels of sitting were first highlighted in
the 1950s when J. Morris et al identified a twofold increase
in the risk of a myocardial infarction in London bus drivers
compared with active bus conductors [1]. In the following
60 years research has focused on establishing the links between
moderate-to-vigorous intensity physical activity (MVPA) and
health, largely overlooking the potentially important distinc-
tion between sedentary (sitting) and light-intensity physical
activity. The opportunities for sedentary behaviour in modern
society, such as watching television (TV), sitting in a car or
using the computer, are ubiquitous. As such, sedentary behav-
iours are an important facet of human lifestyle. Objective
measures have demonstrated that the average adult spends
50–60% of their day in sedentary pursuits [2].

Conclusions/interpretation Sedentary time is associated
with an increased risk of diabetes, cardiovascular disease
and cardiovascular and all-cause mortality; the strength of
the association is most consistent for diabetes.
 Study 2: Published in The British Journal of Sports Medicine:
  • "Television viewing time and reduced life expectancy: a life table analysis" 
  • Reported on in the New York Times: "ccording to the survey data, in 2008, the year that the researchers chose as their benchmark, Australian adults viewed a collective 9.8 billion hours of television. Using complex actuarial tables and adjusting for smoking, waist circumference, dietary quality, exercise habits and other variables, the scientists were next able to isolate the specific effect that the hours of sitting seemed to be having on people’s life spans. And the findings were sobering: Every single hour of television watched after the age of 25 reduces the viewer’s life expectancy by 21.8 minutes.By comparison, smoking a single cigarette reduces life expectancy by about 11 minutes, the authors said.Looking more broadly, they concluded that an adult who spends an average of six hours a day watching TV over the course of a lifetime can expect to live 4.8 years fewer than a person who does not watch TV.  Those results hold true, the authors point out, even for people who exercise regularly. It appears, Dr. Veerman says, that “a person who does a lot of exercise but watches six hours of TV” every night “might have a similar mortality risk as someone who does not exercise and watches no TV.” 

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