Research Review By Dr. Joshua Plener©


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Date Posted:

January 2023

Study Title:

Effectiveness of an intervention for reducing sitting time and improving health in office workers: three arm cluster randomized controlled trial


Edwardson C, Biddle S, Clemes S, et al.

Author's Affiliations:

Diabetes Research Centre, University of Leicester, United Kingdom; NIHR Leicester Biomedical Research Centre; Centre for Health Research, University of Southern Queensland, Australia; School of Sport, Exercise and Health Sciences, Loughborough University, United Kingdom

Publication Information:

British Medical Journal (BMJ) 2022; 378: e069288.

Background Information:

Many adults (and younger people!) spend a large portion of their day sedentary (1-3). In particular, office-based workers have been found to spend 73% of their workday and 66% of their waking day sitting (4)! The emergence of recent evidence linking a high amount of sedentary time to downstream, deleterious health consequences such as increased risk of cardiovascular disease, type 2 diabetes, cancers, anxiety/depression and other health issues exemplifies the need for work and lifestyle modifications for many working adults.

Various interventions have been targeted to reduce sitting time in the workplace and although promising results have been found, the quality of these evaluations have been ‘very low’ to ‘low’ quality of evidence due to various methodological concerns (5). Two recent, large RCTs evaluated multicomponent interventions aimed at reducing sedentary behavior involving a height adjustable desk and found a difference of 45 minutes per eight-hour workday in sitting time in favour of the intervention compared to the control (6, 7). However, these studies only focused on sitting time at work and showed no impact on behavior outside of work. Furthermore, these workplace interventions have been delivered alongside a height adjustable desk and therefore there isn’t an understanding if the effect of an intervention aimed at reducing sitting time without a height adjustable desk would be equally as effective.

To address these research gaps, these authors conducted a large, multisite, cluster randomized controlled trial among desk-based employees. The primary objective was to evaluate the effect of a Smart Work and Life (SWAL) intervention, with and without a height adjustable desk, on daily sitting time during and outside of work, compared with usual practice at a 12-month follow-up. If both interventions were shown to be effective compared to the control group, a secondary objective was to determine if one intervention was more effective than the other.

Pertinent Results:

In total, 756 participants across 78 (office location) clusters were randomized: 26 (locations) to the control arm, 27 to the intervention (SWAL) arm and 25 to the intervention (SWAL) plus standing desk arm. At three months, 12.3% of participants dropped out and at 12 months, 22.2% of participants had dropped out.

Although 51 out of the 52 intervention clusters had training or a workplace champion, by the end of the study, 21% of the intervention clusters didn’t have a champion. Across both intervention arms, 79% of participants completed some or all of the online education.

The intervention groups (SWAL and SWAL + standing desk) showed favourable changes compared to the control group in daily sitting time at three and 12 months. When assessing the primary outcome, the SWAL intervention with a desk group sat for 41.7 minutes less per day than the SWAL intervention without a desk group (who themselves sat for ~20 minutes less than the control group). This means the SWAL plus desk group reduced their sitting time by ~60 minutes! For both intervention groups, self-reported sitting and physical activity variables were found to have favorable changes in the percentage of time sitting, prolonged sitting, and standing at the 3- and 12-month follow-ups compared with the control group. As well, there were small favourable changes in stress and wellbeing in both intervention groups compared to the control group.

During the study, 22.4% of participants reported at least one adverse event. 25% of adverse events were related to irritation from wearing the accelerometer, 0.9% as a result of back pain, 2.3% of adverse events were attributed to pain during the blood test and 72% were unrelated to the study.

Clinical Application & Conclusions:

Both intervention groups were shown to be effective for reducing sitting time compared to the control group. Adding a standing desk to the intervention demonstrated greater effectiveness than the intervention without a standing desk (perhaps this is a case where the more tools you provide, the greater the chance of the intervention succeeding?). Compared to the control group, the standing intervention with a height adjustable desk resulted in more than a 60-minute reduction in daily sitting time, suggestive of a clinically relevant difference which could potentially improve health outcomes. Furthermore, it was found that there was a significant interaction occurring for age, as the intervention plus desk group was more effective during working hours for individuals older than 46 years of age.

Some suggest that an increased time standing could result in an increase in musculoskeletal pain, such as low back pain and lower extremity symptoms (8). In theory, standing still could be just as harmful as sitting still, right? A systematic review of workplace interventions aimed at reducing sitting times found that the effects on musculoskeletal symptoms are unclear, with studies showing either small improvements, worsening of symptoms or no change in symptoms (5). In this study, all three groups had a decrease in the prevalence of musculoskeletal problems as well as their pain rating scores. Therefore, despite the increased time standing, musculoskeletal symptoms and pain didn’t increase.

Future research can assess how people can be best supported to make changes outside of work, conduct implementation studies across different employment sectors, and follow participants for a longer period of time.

EDITOR’S NOTE: Sitting can certainly be a damaging physical input for some people, exacerbating any number of aches and pains. I think this study showed some promise in a multifaceted approach, consisting of a structured program with or without a standing desk (‘with’ being preferable). The reality is, a standing desk may not be physically, nor financially, available to some, so as clinicians we must aim to make movement a part of a daily routine for our patients who need to sit a lot. Another thing to remember is that sitting often doesn’t stop when someone leaves their office or workspace – many people commute/drive (more sitting!), then get home and sit some more (meals, television etc.). As always, encouraging movement or exercise of any type can have a massive impact and in the case of combatting the effects of sitting, even brief postural relief exercises interspersed throughout the day can benefit our patients. Make the recommendations easy to implement, start small and build healthy habits.

Study Methods:

This study was a three-arm cluster randomized controlled trial with follow-ups at 3 and 12 months.

Participants were eligible if:
  • Aged 18 years and older
  • Spend most of their day sitting
  • Worked at least 60% of full time equivalent
  • Could give informed consent and could walk unassisted
Individuals were excluded if they were pregnant, already using a height adjustable desk, and/or were unable to provide informed consent.

Intervention Groups:
The Smart Work and Life (SWAL) intervention was modified based on a previous intervention that was shown to be successful in reducing occupational sitting time over 12 months (6). SWAL focuses on a whole day approach in order to reduce sitting time and is designed for implementation by trained workplace champions within the target organization. The intervention includes a range of multifaceted strategies which draw upon principals of behavior change. These strategies include organizational strategies, environmental strategies, and individual and group strategies. Organizational strategies include gaining the support of senior leaders through a series of business documents and videos, articulating the importance of reducing employee sitting behaviors and explaining how a reduction in sitting time can occur without disrupting performance and productivity. In addition, ‘workplace champions’ were used who were employees enrolled in the study who developed and implemented skills to facilitate the interventions. Environmental strategies included a small scale restructuring of the office environment to encourage more frequent movement around the office and think about their home environment as well. Participants were provided an information booklet discussing guidance on how to use the desk appropriately as well as recommendations on how much standing to achieve throughout the day. Group and individual strategies included education sessions on the benefits of reducing one’s sitting time, encouraging participants to reflect on their own practices to identify barriers and set goals, and provide resources to look at. The main message provided was to sit less, ideally less than 50% of the waking day, and move more often, ideally every 30 minutes (9). Group sessions were encouraged to provide and review key messages of the intervention and discuss barriers and facilitators to reduce sitting time.

The second intervention group partook in the SWAL program and were provided with a sit-stand desk. The control group carried on as usual during the study without any intervention applied to them.

The main outcome measures were daily sitting time at the 12-month follow-up, as measured by an accelerometer that distinguishes between sitting or lying down, static standing, stepping time and transition between sitting and standing (10). Participants were asked to wear the device for 24 hours a day for eight days. The secondary outcomes were measured at three and 12 months for the sedentary behavior, physical activity and lifestyle variables, physical health, and mental health, and work related health and performance, as well as adverse events.

Statistical Analysis:
After the collection of the data, it was checked for any occasions that were misclassified as determined by self-reported wake and sleep times. A valid “wear day” for the workday, and non-workday was defined as wearing the device for 10 or more hours daily, achieving over 1000 steps and spending less than 95% of the day in any one behavior (11). To be included in the analysis, participants had to have at least one valid day which was defined as detection of wearing the device for greater than 16 hours within a 24 hour window.

A sample size of 690 participants from 72 clusters were needed to provide more than 90% power for the primary outcome. An intention-to-treat analysis and a per-protocol analysis were carried out.

Study Strengths / Weaknesses:

  • This study was a large, cluster randomised controlled trial and featured rigorous methodology.
  • The intervention mimicked a real world intervention delivery.
  • Participants were recruited across various areas of England, which increases the generalizability of the findings.
  • The authors planned to conduct a 24 month follow-up assessment, but were unable to due to the COVID-19 pandemic.
  • Over 20% of participants had dropped out of the study by the 12 month follow-up – this may have affected their results.
  • Accelerometers were used which reduces bias of self-reported findings, but participants may have behaved differently while wearing them.

Additional References:

  1. Loyen A, Clarke-Cornwell AM, Anderssen SA, et al. Sedentary Time and Physical Activity Surveillance Through Accelerometer Pooling in Four European Countries. Sports Med 2017; 47: 1421-35.
  2. Hamer M, Stamatakis E, Chastin S, et al. Feasibility of Measuring Sedentary Time Using Data From a Thigh-Worn Accelerometer. Am J Epidemiol 2020; 189: 963-71.
  3. van der Berg JD, Stehouwer CDA, Bosma H, et al. Associations of total amount and patterns of sedentary behaviour with type 2 diabetes and the metabolic syndrome: The Maastricht Study. Diabetologia 2016; 59: 709-18.
  4. Prince SA, Roberts KC, Reed JL, et al. Daily physical activity and sedentary behaviour across occupational classifications in Canadian adults. Health Rep 2020; 31: 13-26.
  5. Shrestha N, Kukkonen-Harjula KT, Verbeek JH, et al. Workplace interventions for reducing sitting at work. Cochrane Database Syst Rev 2018; 6: CD010912.
  6. 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.
  7. Healy GN, Eakin EG, Owen N, et al. A Cluster Randomized Controlled Trial to Reduce Office Workers’ Sitting Time: Effect on Activity Outcomes. Med Sci Sports Exerc 2016; 48: 1787-97.
  8. Coenen P, Willenberg L, Parry S, et al. Associations of occupational standing with musculoskeletal symptoms: a systematic review with meta-analysis. Br J Sports Med 2018; 52: 176-83.
  9. Dempsey PC, Sacre JW, Larsen RN, et al. Interrupting prolonged sitting with brief bouts of light walking or simple resistance activities reduces resting blood pressure and plasma noradrenaline in type 2 diabetes. J Hypertens 2016; 34: 2376-82.
  10. Grant PM, Ryan CG, Tigbe WW, et al. The validation of a novel activity monitor in the measurement of posture and motion during everyday activities. Br J Sports Med 2006; 40: 992-7.
  11. Winkler EAHH, Bodicoat DH, Healy GN, et al. Identifying adults’ valid waking wear time by automated estimation in activPAL data collected with a 24 h wear protocol. Physiol Meas 2016; 37: 1653-68.

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