A cluster randomized controlled trial to reduce office workers' sitting time: impact on activity outcomes

PURPOSE: To evaluate, compared to usual practice, the initial and long-term effectiveness of a workplace intervention targeting reducing sitting on activity outcomes.

METHODS: Office worksites (≥1km apart) from a single organization in Victoria, Australia were cluster randomized to intervention (n=7) or control (n=7). Participants were 231 desk-based office workers (5 to 39 participants per worksite) working at least 0.6 full time equivalent. The workplace-delivered intervention addressed organizational, physical environment, and individual behavioural change to reduce sitting time. Assessments occurred at baseline, three-, and 12-months, with the primary outcome participants' objectively measured (activPAL3 device) workplace sitting time (mins/8-h workday). Secondary activity outcomes were: workplace time spent standing, stepping (light, moderate-vigorous and total) and in prolonged (≥30min) sitting bouts (h/8-h workday); usual duration of workplace sitting bouts; and, overall sitting, standing and stepping time (mins/16-h day). Analysis was by linear mixed models, accounting for repeated measures and clustering and adjusting for baseline values and potential confounders.

RESULTS: At baseline, on average, participants (68% women; mean±SD age = 45.6±9.4 years) sat, stood and stepped for 78.8±9.5%, 14.3±8.2%, and 6.9±2.9% of work hours respectively. Workplace sitting time was significantly reduced in the intervention group compared to the controls at three months (-99.1 [95% CI -116.3 to -81.8] min/8-h workday) and 12 months (-45.4 [-64.6 to -26.2] min/8-h workday). Significant intervention effects (all favoring intervention) were observed for standing, prolonged sitting, and usual sitting bout duration at work, as well as overall sitting and standing time, with no significant nor meaningful effects observed for stepping.

CONCLUSIONS: This workplace-delivered multicomponent intervention was successful at reducing workplace and overall daily sitting time in both the short- and long- term.