Tuesday October 13 2015
Simply standing still is no substitute for exercise
"Sitting down at work no worse than standing up," ITV News reports. A new study seems to contradict earlier advice – including recommendations on this website – that standing rather than sitting at work could bring health benefits and reduce the risk of early death.
The study featured more than 5,000 civil servants who provided information on their average sitting time doing different activities such as working, watching TV, or other leisure activities in the late 90s.
They were followed for 16 years to see if sitting time increased the risk of dying from any cause. The results showed no significant association between sitting time and risk of death.
However, the study sample only included white collar employees. And the majority of the participants were Londoners, who tend to walk and stand more as a result of the unique "challenges" posed by public transport in the capital. This means the results may not be applicable to other parts of the country.
These limitations aside, does this mean expensive standing work stations and desks are a waste of money? The lead author seems to think so: "The results cast doubt on the benefits of sit-stand work stations."
Ultimately, simply standing up is no substitute for the moderate to vigorous exercise regime recommended for healthy adults. It could be the case employers are better off investing in gym membership than new desks for their employees.
Where did the story come from?
The study was carried out by researchers from the University of Exeter, University College London, and the University of Sydney (Australia).
It was funded by multiple UK organisations, such as the British Heart Foundation, Stroke Association, the National Heart and Lung Institute, and the National Institute on Aging.
The study was published in the peer-reviewed International Journal of Epidemiology on an open access basis, so it is free to read online or download as a PDF.
It was widely reported on by the UK media, accurately for the most part. The Guardian reported the story accurately and responsibly, but the Daily Mail's headline was exaggerated and misleading: "Couch potatoes rejoice! Sitting for long periods is NOT bad for your health, study claims."
This interpretation of the results of the study is incorrect and potentially dangerous. Sitting down may not be as bad for your health as previously thought, but it is still bad for your health.
The study only looked at overall mortality, not specific health outcomes. So sitting down all day may not kill you, but it could contribute towards your obesity or type 2 diabetes risk. Conversely, the benefits of an active lifestyle are well known.
The Guardian quoted one of the authors of the study, Melvyn Hillsdon, who said: "Any stationary posture where energy expenditure is low may be detrimental to health, be it sitting or standing."
He added: "The results cast doubt on the benefits of sit-stand work stations, which employers are increasingly providing to promote healthy working environments."
What kind of research was this?
This cohort study aimed to assess the association between sitting time and risk of dying in a large group of UK adults with a follow-up period of 16 years.
The researchers considered four sitting indicators for their analysis:
- work sitting
- TV viewing time
- non-TV leisure time sitting
- total leisure time sitting
They say previous research suggested an association between sitting behaviours and increased risk of mortality, cardiovascular diseases and metabolic diseases. This study aimed to add to that evidence base by examining different types of sitting along with total time sitting and risk of death.
Cohort studies of this type, which include a large population with a long follow-up period, can tell us if there is any association between an exposure and an outcome – but this cannot prove direct causality.
What did the research involve?
This research included 5,132 individuals (3,720 men and 1,412 women) from a London employee-based longitudinal study of the British Civil Service, the Whitehall II study. These individuals were free of heart and vascular diseases at the start of the study period.
This study started in 1985 and included civil servants aged between 35 and 55 from clerical and office support, middle-ranking executive and senior administrative grades. The researchers took data from phase 5 (1997-99) of this study, when information on sitting behaviour was collected.
At the start of the study, all the participants completed a questionnaire and underwent a clinical examination. Subsequent measurements were done either through a postal questionnaire alone or a postal questionnaire accompanied by a clinical examination.
In phase 5, participants provided information on work and leisure time sitting behaviours. They reported on average how many hours they spent sitting at work (including driving or commuting) and sitting at home (such as watching TV or sewing) by selecting from eight response categories (none, 1 hour, 2-5, 6-10, 11-20, 21-30, 31-40, 40 or more hours).
Mortality data was collected through the national mortality register by the National Health Service (NHS) Central Registry.
Researchers also collected data on various factors that might influence the results (confounders), such as:
- sociodemographic factors – age, gender, ethnicity and employment grade
- health-related factors – smoking status, alcohol consumption, diet quality, BMI, physical functioning and physical activity
What were the basic results?
Over 16 years, 450 deaths were recorded among the 5,132 participants. Overall, the study found no statistically significant links between any of the five sitting indicators and risk of death.
In analyses adjusted for age, gender, employment grade and ethnicity, there was no difference in mortality risk for:
- individuals with 0-8 hours of work sitting time compared with those with more than 40 hours of work sitting a week (hazard ratio [HR] 0.81, confidence interval [CI] 0.57 to 1.14)
- individuals with 0-8 hours of TV time compared with those with more than 16 hours of TV sitting time a week (HR 1.30, CI 0.88 to 1.13)
- individuals with 0-4 hours of non-TV leisure time compared with those with more than 16 hours of non-TV leisure sitting time a week (HR 0.92, CI 0.66 to 1.28)
- individuals with 0-15 hours of leisure time compared with those with more than 26 hours of leisure sitting time a week (HR 1.36, CI 1.05 to 1.75)
- individuals with 0-26 hours of total time sitting compared with those with more than 55 hours of total sitting time a week (HR 0.95, CI 0.72 to1.27)
How did the researchers interpret the results?
The researchers concluded by saying: "It is possible that previously reported relationships between sitting time and health outcomes are due to low daily energy expenditure, the best solution to which is to increase daily physical activity even at light intensities."
They added: "Until more robust epidemiological and mechanistic evidence exists about the risks of prolonged sitting, the promotion of a physically active lifestyle should still be a priority."
This cohort study aimed to assess the association between sitting time and overall risk of death in a large sample of UK civil servants with a follow-up period of 16 years.
The results showed no association between sitting time and risk of death. The results of this study have relevance for policy makers and employers to promote recommended daily physical activity.
While this study reports some interesting findings, the results should be interpreted with some caution because of the study's limitations. The study does have strengths in its large sample size, long duration of follow-up period, and examination of mortality outcomes through a national register.
However, as acknowledged by the researchers, this Whitehall study only included white collar employees, mainly based in London, so the results cannot be generalised to all populations.
It is also possible people may not be able to give reliable estimates of their sitting time, and these one-off measures taken at the end of the 90s are not representative of lifelong sedentary and activity patterns.
And although the researchers adjusted for some confounding factors, there may be various other health and lifestyle factors that are not considered in the analysis that might have had an influence on the results.
But the findings do not suggest you can regularly sit for long periods and get no exercise but still maintain good health. Sitting down on a regular basis may not directly increase your risk of death, but it could contribute towards the risk of developing chronic diseases such as type 2 diabetes and obesity, which can have an adverse impact on your quality of life.
The importance of healthy eating and daily physical exercise to maintain good health are well recognised. Current physical activity recommendations for adults are 150 minutes of moderate aerobic activity a week, accompanied by strength exercises on two or more days of the week.