Currently submitted to: Journal of Medical Internet Research
Date Submitted: Mar 25, 2026
Open Peer Review Period: Mar 25, 2026 - May 20, 2026
(currently open for review)
Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.
A mobile health intervention promoting physical activity to reduce psychological distress among workers: A randomized controlled trial
ABSTRACT
Background:
Evidence on whether mobile health (mHealth) interventions targeting physical activity can reduce psychological distress among generally healthy workers is limited.
Objective:
This study aimed to investigate the effectiveness of a standalone smartphone app that passively monitors physical activity and mental health in reducing psychological distress among workers.
Methods:
This open-label, 2-arm, parallel-group randomized clinical trial was conducted in Japan over 6 months, with assessments at baseline, 3 months, and 6 months. Eligible participants were workers aged 18 years or older who were able to complete the Japanese questionnaires and owned compatible smartphones. Individuals currently absent from work or with a history of absence within the past 12 months were excluded. Participants were randomized (1:1) to the intervention or control group. Participants in the intervention group used a smartphone app that passively monitors physical activity and mental health for 3 months. The control group received a booklet on job stress and stress management. The primary outcome was psychological distress measured using the K6 scale. Secondary outcomes included self-reported physical activity and digitally recorded activity duration in the intervention group. Analyses followed the intention-to-treat principle. For the main analysis, linear mixed modeling for repeated measures was used to estimate between-group differences in changes in psychological distress across the three time points.
Results:
A total of 793 workers were randomized (intervention: n=397; control: n=396). Psychological distress decreased significantly in the intervention group at three months (mean difference = −0.56, 95% CI: −1.11 to −0.02; P = .04; Cohen’s d = −0.17), although this effect was not sustained at six months. Subgroup analysis showed a larger effect among participants with no or minimal baseline distress (mean difference = −0.63, 95% CI: −1.16 to −0.11; P = .02; Cohen’s d = −0.19). Although self-reported physical activity declined in both groups without significant between-group differences, digitally recorded activity in the intervention group increased during the intervention period (7.92 min increase, 95% CI: 1.36 to 14.49; P = .02).
Conclusions:
The standalone smartphone-based app modestly reduced psychological distress among workers, with clearer evidence among those with no or minimal psychological distress at baseline. Mobile health interventions enabling workers to monitor physical activity and mental health may contribute to preventing mental health problems in workplace settings. Clinical Trial: UMIN-CTR Identifier: UMIN000057908; https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000066193
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