Clinical trial NCT02496507: A Mixed-methods Evaluation of Sit-stand Workstations in an Office Setting
Official title: A Mixed-methods Evaluation of Sit-stand Workstations in an Office Setting: a Randomised Controlled Trial
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Physical Activity
Keywords: sitting
intervention
desks
workplace
cardiovascular
metabolic
qualitative
randomised controlled trial
Lead sponsor: Liverpool John Moores University
Sponsor class: OTHER
First posted: 2015-07-14
Enrollment: 47
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: BASIC_SCIENCE

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%.

Eligibility criteria: Inclusion Criteria:

* full-time member of staff
* access to a work telephone and desktop computer with internet

Exclusion Criteria:

* have a cardiovascular or metabolic disease
* taking any medication
* pregnant
* planned absence \> 1 week during the trial

Primary outcomes:
measure: Change from baseline in workplace sitting time at 4 and 8 weeks
timeFrame: Baseline (week 0), Mid-intervention (4 weeks), End-intervention (8 weeks)
Secondary outcomes:
measure: Change from baseline in workplace standing time at 4 and 8 weeks
timeFrame: Baseline (week 0), Mid-intervention (4 weeks), End-intervention (8 weeks)
measure: Change from baseline in workplace walking time at 4 and 8 weeks
timeFrame: Baseline (week 0), Mid-intervention (4 weeks), End-intervention (8 weeks)
measure: Change from baseline in flow-mediated dilation (FMD) at 8 weeks
timeFrame: Baseline (week 0), End-intervention (8 weeks)
measure: Change from baseline in carotid artery intima media thickness (cIMT) at 8 weeks
timeFrame: Baseline (week 0), End-intervention (8 weeks)
measure: Change from baseline in plasma glucose at 8 weeks
timeFrame: Baseline (week 0), End-intervention (8 weeks)
measure: Change from baseline in triglycerides at 8 weeks
timeFrame: Baseline (week 0), End-intervention (8 weeks)
measure: Change from baseline in total cholesterol at 8 weeks
timeFrame: Baseline (week 0), End-intervention (8 weeks)
measure: Change from baseline in musculoskeletal discomfort or pain at the neck/shoulders at 8 weeks
timeFrame: Baseline (week 0), End-intervention (8 weeks)
measure: Change from baseline in musculoskeletal discomfort or pain at the lower back at 8 weeks
timeFrame: Baseline (week 0), End-intervention (8 weeks)
measure: Change from baseline in musculoskeletal discomfort or pain at the upper back at 8 weeks
timeFrame: Baseline (week 0), End-intervention (8 weeks)
measure: Change from baseline in body mass index at 8 weeks
timeFrame: Baseline (week 0), End-intervention (8 weeks)
measure: Acceptability of the sit-stand workstation
timeFrame: End-intervention (8 weeks)
measure: Feasibility of the sit-stand workstation
timeFrame: End-intervention (8 weeks)
measure: Acceptability of the sit-stand workstation
timeFrame: End-intervention (8 weeks)
measure: Feasibility of the sit-stand workstation
timeFrame: End-intervention (8 weeks)
Other outcomes:
Locations:
city: Liverpool
country: United Kingdom
facility: Liverpool John Moores University
state: Merseyside
Study officials:
affiliation: Liverpool John Moores University
name: Lee EF Graves, PhD
role: PRINCIPAL_INVESTIGATOR
References:
citation: Batterham AM, Hopkins WG. Making meaningful inferences about magnitudes. Int J Sports Physiol Perform. 2006 Mar;1(1):50-7.
citation: Hopkins WG, Marshall SW, Batterham AM, Hanin J. Progressive statistics for studies in sports medicine and exercise science. Med Sci Sports Exerc. 2009 Jan;41(1):3-13. doi: 10.1249/MSS.0b013e31818cb278.
citation: E F Graves L, C Murphy R, Shepherd SO, Cabot J, Hopkins ND. Evaluation of sit-stand workstations in an office setting: a randomised controlled trial. BMC Public Health. 2015 Nov 19;15:1145. doi: 10.1186/s12889-015-2469-8.