An office-based intervention involving a height-adjustable workstation and instruction package reduced the amount of time spent sitting. Workers sat for around 60 to 90 minutes less per day at six and 12 months compared with the control group.
Sitting for long periods is a risk factor for ill health even in people meeting recommended levels of physical activity. Reducing time sitting at work could have health and economic benefits, but the evidence is limited. This trial was fairly small, involving 146 NHS workers. No firm conclusions can be drawn as to whether reduced sitting time may translate into effects on musculoskeletal health, work performance or sickness absence. However, the results are promising and will be important if shown to be effective and cost-effective for individuals and their employers when implemented more widely.
A larger NIHR-funded study involving council workers is underway which may provide further evidence and cost data.
Why was this study needed?
It’s estimated that over a third of people in the UK (about 20 million) do not meet suggested physical activity targets. Low levels of physical activity are linked with cardiovascular disease, type 2 diabetes, certain cancers and general ill health. Prolonged sitting is thought to slow the body’s metabolism, affect blood sugar regulation, blood pressure and amount of fat burned. It’s a recognised risk factor even among people who meet government physical activity targets. The NHS advises people to get up after sitting for 30 minutes.
Office workers are estimated to spend three-quarters of their working hours sitting. A 2018 Cochrane review looked at interventions to reduce sedentary time at work. There was insufficient evidence for most interventions, but low-quality evidence that height-adjustable desks may reduce sitting time at work by 100 minutes a day at up to three months. This study was commissioned to look at sitting time after longer follow-up.
What did this study do?
The NIHR-funded SMarT cluster randomised trial assigned 37 office departments within the three hospitals of the University Hospitals of Leicester NHS Trust to the 12-month intervention or control. One hundred and forty-six people working at least three days weekly at the same desk chose to participate.
The intervention involved an initial seminar covering the health consequences of prolonged sitting; tracking of participants’ normal daily sitting and activity levels using a wearable wrist device that captures time spent in moderate or vigorous activity (the activePAL device); a personalised action plan; provision of a height-adjustable desk and chair cushion that vibrated after pre-set periods to remind the person to get up. Educational/motivational leaflets and brief coaching sessions were provided every few months.
The activePAL data was shared with intervention participants at each follow-up. Activity levels were measured in the control group, but they received no feedback. Assessors were unaware of group assignment. Thirty three per cent of control and 17% of intervention participants did not complete follow-up.
What did it find?
- At 12 months, people using the SMarT Work intervention sat for 81.64 minutes less at work each day than people in the control group (95% confidence interval [CI] 112.27 to 51.01 minutes less). This was analysis of all participants by intention-to-treat, though analysis of only those who completed follow-up gave similar results (-83.28, 95% CI -116.57 to -49.98).
- Reductions in occupational sitting time were also seen at three (-50.62, 95% CI -78.71 to -22.54) and six month (-64.40, 95% CI -97.31 to -31.50) follow-up (data for complete cases only).
- There was a similar reduction in total daily sitting time, and increases in occupational standing time and total daily standing time at all time-points compared with the control group. However, there was no difference between groups in either total daily activity or daily stepping time at any follow-up.
- The SMarT intervention gave some improvement in work-related outcomes of work engagement and job performance at six and 12 months (about 0.5 point improvement on a 7-point scale). It also gave some improvement in presenteeism (continuing at work with health problems) but had no effect on sickness absence.
- Effects of the intervention on musculoskeletal problems, mood, and quality of life were mixed.
What does current guidance say on this issue?
NICE’s 2008 guideline on physical activity in the workplace has no recommendations on standing desks. Recommendations aimed at workers focus on encouraging walking and cycling to work, using stairs instead of lifts, and moving around more in the workplace. Other recommended actions include employers providing information on walking and cycling routes and encouraging people to set goals for distances walked or cycled.
An update review by NICE in January 2019 found that this study's findings supported existing recommendations to reduce sitting time at work. NICE plans to update the physical activity in the workplace guideline to include the ongoing SMArT Work & Life trial (expected 2021).
What are the implications?
The findings provide encouragement for organisations thinking about introducing standing desks. However, people choosing to participate in the study may be more motivated to standing at work than other employees.
The study was also small and did not have power to detect reliable differences for outcomes other than time sitting. As these results are promising it is likely that the characteristics or workplaces and the people that benefit will need further study before costs can be justified.
The results of the larger study of the SMarT intervention will assess longer-term outcomes over two years in 660 office workers in England. This may assist in any review of guidance and would be an opportunity to gather cost data too. This will be important for employers and the NHS if wider use is recommended.
Citation and Funding
Edwardson CL, Yates T, Biddle SJH et al. Effectiveness of the Stand More AT (SMArT) Work intervention: cluster randomised controlled trial. BMJ. 2018;363:k3870.
This project was funded by the National Institute for Health Research Department of Health Policy Research Programme (project number PR-R5-0213-25004).
British Heart Foundation. Physical inactivity and sedentary behaviour report 2017. Birmingham: British Heart Foundation; 2017.
NHS website. Why we should sit less. London: Department of Health and Social Care; updated 2016.
NICE. Physical activity in the workplace. PH13. London: National Institute for Health and Care Excellence; 2008.
NICE. 2019 exceptional surveillance of physical activity in the workplace (NICE guideline PH13). London: National Institute for Health and Care Excellence; 2019.
Shrestha N, Kukkonen‐Harjula KT, Verbeek JH et al. Workplace interventions for reducing sitting at work. Cochrane Database Syst Rev. 2018;(12):CD010912.
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