Mindfulness meditation has been reported to reduce stress and enhance well-being. However, its effects on heart rate variability (HRV)-a physiological marker of stress-remain underexplored. This study aimed to examine how meditation practice is associated with subjective stress, HRV, and their interaction, using mobile health (mHealth) technologies. This three-week observational study included 90 participants: 19 meditation practitioners (meditation group), 32 recreational runners as an active control group characterized by lower stress and higher HRV (running group), and 39 individuals without regular meditation or exercise habits (control group). HRV was continuously recorded using Garmin smartwatches. Subjective stress levels and activity states were assessed three times daily through a smartphone-based experience sampling method (ESM), yielding a total of 4,557 responses (mean = 51.8 per participant). From the meditation group, start and end times of 632 daily meditation practices (mean = 33.3 per participant) were also collected via the app. Standardized questionnaires on stress and related measures were administered at the end of the study period. The questionnaire survey confirmed that stress levels were significantly lower in both the meditation and running groups compared to controls (median Perceived Stress Scale scores; 21 [meditation], 22 [running], and 25 [control]; Kruskal-Wallis P = .024; adjusted Wilcoxon P = .048 and .040, respectively). Smartwatch-derived HRV (RMSSD) was elevated in the running group relative to controls (medians: 47.0 and 42.0, respectively; P < .001), whereas no significant difference was observed between the meditation and control groups (medians: 40.8 and 42.0, respectively). Bayesian analysis of the ESM data indicated that higher subjective stress levels were associated with a concurrent RMSSD reduction of -2.24 ms (95% credible interval: -3.97 to -0.26). Although this pattern was consistent across groups, the steeper decline of -3.94 ms (95% CI: -7.04 to -0.74) was observed only in the running group, likely reflecting their elevated baseline HRV. Additionally, Bayesian modeling of 632 logged meditation sessions revealed an acute RMSSD increase of +4.68 ms (95% CI: 2.96 to 6.38) during meditation, with effects sustained for at least 30 minutes post-practice. Although HRV among meditation practitioners did not appear elevated in overall daily life, the ability to increase HRV at arbitrary timings, along with the prolonged residual effect, may correlate with stress reduction. This hypothesis requires further exploration with adequate controls. Despite the preliminary nature of this study due to its limited sample size, our findings highlight the potential of mHealth-based methodologies to capture stress and HRV dynamics in real-world settings.

The authors have declared no competing interest.

This study did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Garmin Japan Ltd. provided electronic coupons to some participants as part of their compensation for participation.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethics Review Board of the Institute of Medical Science, The University of Tokyo gave ethical approval for this work (Approval Number: 2022-11-0629). Human Subject Research Ethics Review Committee of Tokyo Institute of Technology gave ethical approval for this work (Approval Number: 2022154).

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The datasets generated and analyzed during this study are available from the corresponding author on reasonable request.