Digital nudge emails to increase early registration for an occupational health support program: a stratified randomized controlled trial

Objective: To evaluate whether nudge emails increased early registration for an occupational health support program among employees advised to act after annual health checkups. Methods: In this stratified randomized controlled trial, 871 employees with no documented action after health checkup recommendations were randomized to nudge or standard emails. The primary outcome was registration by July 12, 2022, before a universal desktop reminder; the secondary outcome was registration by July 20, 2022. Adjusted odds ratios were estimated using logistic regression. Results: Among 749 analyzed employees, registration in the unexamined/incomplete-action group was higher with nudge emails than with standard emails (64.7% vs 50.9%; adjusted odds ratio, 1.81; 95% CI, 1.32–2.47). No significant difference was observed among non-responders. Conclusions: Nudge emails accelerated early registration, particularly among employees who had not yet acted.