A Mixed-methods Evaluation of Sit-stand Workstations in an Office Setting
- Conditions
- Physical Activity
- Interventions
- Other: Sit-stand workstation
- Registration Number
- NCT02496507
- Lead Sponsor
- Liverpool John Moores University
- Brief Summary
The purpose of this study is to investigate whether a device that allows office workers to sit or stand whilst working can reduce their sitting time at work and improve their health over 8 weeks.
- Detailed Description
Study design
Treatment arms in this two-arm parallel-group randomised controlled trial (RCT) included a sit-stand workstation intervention group (each participant received a sit-stand workstation) and a control group (usual practice).
Recruitment
- Organisation level
Office workers from one organisation were targeted by the research team in August-September 2013. Consent was sought from 11 departmental managers for employee recruitment, installation of sit-stand workstations, study contact and laboratory visits during work time. Departments were located across four buildings with varying office layout (open-plan, individual offices or a combination). Employees within the targeted departments were predominantly administrative staff.
- Individual level
Via an email from the research team, all employees in consenting departments received an overview of the study and participant information sheet, and were invited to a study information session (two sessions were organised per department). Employees were given 2 weeks to express interest. Interested employees were screened for eligibility using stated criteria by the research team via telephone. If inclusion criteria were met, written informed consent was obtained and baseline assessments scheduled. There was no racial or gender bias in the selection of participants.
Group assignment and Intervention
Following baseline assessments, participants were assigned by one member of the research team to a treatment arm using a randomised block design and random number table. Departments served as blocks and participants within departments were randomly assigned at the individual-level to an arm. Assignment of individual participants within each department alternated between arms (i.e. intervention, control, intervention, control...).
Data collection
At baseline, 4 weeks (mid-intervention) and 8 weeks (end-intervention), participants' office-based behaviours were assessed via ecological momentary assessment (EMA) diaries. At baseline and 8 weeks, participants attended University laboratories in the morning for individual assessments of other stated outcomes. Prior to laboratory visits, participants were required to fast for a minimum of 8 hours, avoid the consumption of alcohol for 12 hours, and avoid strenuous exercise for 24 hours.
Sample size
Allowing for small drop out, the study aimed to recruit 25 participants per arm, and retain 23 participants per arm. A sample size of 23 per arm was chosen a priori to achieve 90% power (alpha 5%; two-tailed) to detect a minimum difference of 60 minutes/8-hour workday between arms for workplace sitting time (primary outcome: expected SD of 60 minutes/day). Data collection for vascular and metabolic outcomes would provide effect size estimates for power calculations in subsequent trials.
Statistical analyses
* Data was analysed using the Statistical Package for the Social Sciences (SPSS) version 22 (IBM, New York, USA) with the alpha level set at p≤0.05. Intervention effects were compared at 4 weeks (sitting, standing and walking) and 8 weeks (all outcomes) from baseline using analysis of covariance (ANCOVA). The variable change score (4 or 8 weeks minus baseline) was the dependent variable, with intervention arm (control vs intervention) the independent variable. In all analyses, covariates were the baseline value for the variable to control for any imbalances at baseline. Anthropometric, sociodemographic, work-related and office-environment characteristics were tested as potential confounders for all outcomes. Confounders were entered as covariates if significant associations (p≤0.05) were observed with changes in an outcome and the effect on the mean difference between groups exceeded 20%. For changes in sitting, standing and walking time, baseline values of the other two behaviours were tested as potential confounders, though no effects on the mean difference between groups exceeded 20%. Adjusted change scores and 95% confidence intervals (CIs) for the difference in change between groups are presented unless stated otherwise. Acceptability and feasibility data are reported as medians and quartiles.
* Missing data and Intention-to-treat analysis Due to participant withdrawal, lost EMA diaries or the inability to conduct assessments, data were missing for all outcomes. Accordingly, a per-protocol analysis was conducted and participants were excluded from analyses for outcomes they were missing data for. For workplace sitting, standing and walking, the per-protocol analysis was compared with an intention-to-treat analysis, as a sensitivity analysis. To treat missing data, the fully conditional imputation technique and ten imputation sets were used due to a low rate of missing data. Imputation was based on all 47 randomized participants.
* Minimum important differences analysis Inferential statistics were ran using minimum clinically important difference principles, described elsewhere. Briefly, this approach makes inferences based on meaningful magnitudes and is recommended alongside hypothesis testing. A spreadsheet computed the quantitative and qualitative probability that the true effects were beneficial, trivial or harmful, after the outcome statistic, its p value, and the smallest/minimal important difference was entered. Minimum important differences for sitting and standing were 60 minutes/day, and for walking 10 minutes/day. Minimum important differences for other outcomes were determined through a distribution-based method as a Cohen's d (standardized difference between change scores between groups) of 0.2 between-subjects standard deviations (SDs). The SD of pooled baseline data was used to negate the possibility of individual differences from the intervention influencing the SD at 8 weeks. For each effect at 8 weeks, quantitative probabilities for benefit, trivial and harm, and qualitative descriptors are reported. Effects were interpreted as unclear if probabilities for benefit and harm were \>5%.
Recruitment & Eligibility
- Status
- COMPLETED
- Sex
- All
- Target Recruitment
- 47
- full-time member of staff
- access to a work telephone and desktop computer with internet
- have a cardiovascular or metabolic disease
- taking any medication
- pregnant
- planned absence > 1 week during the trial
Study & Design
- Study Type
- INTERVENTIONAL
- Study Design
- PARALLEL
- Arm && Interventions
Group Intervention Description Intervention Sit-stand workstation Provision of a sit-stand workstation for use at work.
- Primary Outcome Measures
Name Time Method Change from baseline in workplace sitting time at 4 and 8 weeks Baseline (week 0), Mid-intervention (4 weeks), End-intervention (8 weeks) An ecological momentary assessment (EMA) diary assessed time spent sitting, standing, walking and in other activities during work hours over 5 days (Monday-Friday). At 15-minute intervals participants used a diary to record their main behaviour in response to the question: "What are you doing right now?" The options were sitting, standing, walking or other. If other was selected, participants were instructed to write the activity they were doing.
Time spent in each behaviour per day was estimated by multiplying the frequency of recordings by 15. A diary day was considered valid if data entries were provided for ≥75% of time spent at work. Time spent in each behaviour was calculated for each valid day and means were calculated from valid days. To be retained for analyses, participants had to provide ≥2 valid days at each time point.
- Secondary Outcome Measures
Name Time Method Change from baseline in plasma glucose at 8 weeks Baseline (week 0), End-intervention (8 weeks) Assessed via standard venepuncture technique
Change from baseline in flow-mediated dilation (FMD) at 8 weeks Baseline (week 0), End-intervention (8 weeks) A measure of endothelial dysfunction, which is an early and integral manifestation of atherosclerotic disease.
Change from baseline in carotid artery intima media thickness (cIMT) at 8 weeks Baseline (week 0), End-intervention (8 weeks) An early subclinical marker of structural atherosclerosis.
Change from baseline in body mass index at 8 weeks Baseline (week 0), End-intervention (8 weeks) Calculated from assessment of stature and body mass
Acceptability of the sit-stand workstation End-intervention (8 weeks) (Intervention arm only) Interviews
Change from baseline in triglycerides at 8 weeks Baseline (week 0), End-intervention (8 weeks) Assessed via standard venepuncture technique
Change from baseline in total cholesterol at 8 weeks Baseline (week 0), End-intervention (8 weeks) Assessed via standard venepuncture technique
Change from baseline in workplace standing time at 4 and 8 weeks Baseline (week 0), Mid-intervention (4 weeks), End-intervention (8 weeks) An ecological momentary assessment (EMA) diary assessed time spent sitting, standing, walking and in other activities during work hours over 5 days (Monday-Friday). At 15-minute intervals participants used a diary to record their main behaviour in response to the question: "What are you doing right now?" The options were sitting, standing, walking or other. If other was selected, participants were instructed to write the activity they were doing.
Time spent in each behaviour per day was estimated by multiplying the frequency of recordings by 15. A diary day was considered valid if data entries were provided for ≥75% of time spent at work. Time spent in each behaviour was calculated for each valid day and means were calculated from valid days. To be retained for analyses, participants had to provide ≥2 valid days at each time point.Change from baseline in workplace walking time at 4 and 8 weeks Baseline (week 0), Mid-intervention (4 weeks), End-intervention (8 weeks) An ecological momentary assessment (EMA) diary assessed time spent sitting, standing, walking and in other activities during work hours over 5 days (Monday-Friday). At 15-minute intervals participants used a diary to record their main behaviour in response to the question: "What are you doing right now?" The options were sitting, standing, walking or other. If other was selected, participants were instructed to write the activity they were doing.
Time spent in each behaviour per day was estimated by multiplying the frequency of recordings by 15. A diary day was considered valid if data entries were provided for ≥75% of time spent at work. Time spent in each behaviour was calculated for each valid day and means were calculated from valid days. To be retained for analyses, participants had to provide ≥2 valid days at each time point.Change from baseline in musculoskeletal discomfort or pain at the lower back at 8 weeks Baseline (week 0), End-intervention (8 weeks) Assessed via an adapted questionnaire from a previous trial
Change from baseline in musculoskeletal discomfort or pain at the upper back at 8 weeks Baseline (week 0), End-intervention (8 weeks) Assessed via an adapted questionnaire from a previous trial
Change from baseline in musculoskeletal discomfort or pain at the neck/shoulders at 8 weeks Baseline (week 0), End-intervention (8 weeks) Assessed via an adapted questionnaire from a previous trial
Feasibility of the sit-stand workstation End-intervention (8 weeks) (Intervention arm only) Interviews
Trial Locations
- Locations (1)
Liverpool John Moores University
🇬🇧Liverpool, Merseyside, United Kingdom