Work Engagement and Well-being Study (SWELL): a randomised controlled feasibility trial evaluating the effects of mindfulness versus light physical exercise at work

Background: Mindfulness-based programmes (MBPs) are increasingly offered at work, often in online self-guided format, but evidence for effects on work performance (WP) is inconsistent. Objective: This pragmatic randomised controlled feasibility trial assessed procedural uncertainties, intervention acceptability and preliminary effect sizes of an MBP on WP relative to an alternative intervention. Methods: 241 employees from eight employers were randomised (1:1) to a 4-week, self-guided, online MBP or a light physical exercise programme (LE; active control). Feasibility and acceptability measures were primary; WP at postintervention (PostInt) was the primary outcome for preliminary effect size assessment. Secondary outcomes included mental health (MH) and cognitive processes hypothesised to be targeted by the MBP. Outcomes were collected at baseline, PostInt and 12-week follow-up (12wFUP). Prospective protocol: NCT04631302. Findings: 87% of randomised participants started the course; acceptability was high. Retention rates were typical for online trials (64% PostInt; 30% 12wFUP). MBP versus LE offered negligible benefits for WP (PostInt d=0.06, 95% CI −0.19 to 0.32; 12wFUP d=0.02, 95% CI −0.30 to 0.26). Both interventions improved MH outcomes (within-arm ds ≈ −0.40 to 0.58); between-group differences were small (ds ≈ −0.09 to 0.04). Conclusion: The trial is feasible and interventions are acceptable. Results provide little support for a later phase trial comparing an MBP to a light exercise control; procedural challenges are summarised to inform future trials. Clinical implications: MBPs are unlikely to improve WP relative to light physical exercise. Although the MBP improved MH, other active interventions may be similarly efficacious. Trial registration: NCT04631302.