Vital Coach: A Study of Resiliency in Medical Students

Mean daily nocturnal Heart Rate Variability (HRV): Higher = Better

daily nocturnal Resting Heart Rate (RHR): Lower = Better

Mean nightly sleep: Higher = Better

SD of mid-sleep time: Lower = Better

To score the Perceived Stress Scale 4 (PSS-4), first, reverse the scores for questions 2 and 3 (0 becomes 4, 1 becomes 3, 2 stays 2, 3 becomes 1, and 4 becomes 0). Then, add up the scores for all four questions. The total score will range from 0 to 16, with higher scores indicating greater perceived stress.

MBI-GSS scoring involves summing responses for each of its three subscales: emotional exhaustion, cynicism, and professional efficacy, which are rated on a 7-point frequency scale from 0 (never) to 6 (daily). To determine burnout, high scores on exhaustion and cynicism indicate higher burnout, while low scores on professional efficacy suggest greater burnout. These subscale scores are then interpreted separately to understand the level of burnout for each dimension. Each item is rated on a frequency scale (e.g., 0 to 6), and higher or lower scores on each subscale indicate different levels of burnout.

Exam performance for the three exams during the study period is self-reported by participants via a typeform in the application at the study conclusion.

HRV will be assessed using the root mean square of successive differences (RMSSD, ms) to provide a daily individual score derived from nightly photoplethysmography (PPG) wearable-recorded data. All primary endpoints are computed at the individual level and compared by week, using week-level means (averaged from the individual daily scores). Heart Rate Variability (HRV) [RMSSD, ms] Individual Test= Like earlier mentioned tests these will include week-to-week differences for the weeks during the phase (Baseline Week, Study Week, Exam Week, Recovery Week) (ex. HRV_Recovery (during) - HRV_Exam (during) and comparisons with pre/post intervention phases (ex. HRV_Recovery (during) - HRV_Recovery (pre-intervention)).

Group Test= A linear mixed model for HRV and PSS-4 with fixed effects for Week, Phase (0=pre, 1=post, 2=during) and a Week x Phase interaction, plus a random intercept for participant.

Sensitivity Analyses= Paired t-tests (Wilcoxon as nonparametric alternative).

Daily mean RHR (bpm) will be derived from nightly PPG wearable-recorded data. All primary endpoints are computed at the individual level and compared by week using week-level means (averaged from the individual daily scores). Resting Heart Rate (RHR) [bpm] Individual Test= Like earlier mentioned tests these will include week-to-week differences for the weeks during the phase (Baseline Week, Study Week, Exam Week, Recovery Week) (ex. RHR_Recovery (during) - RHR_Exam (during) and comparisons with pre/post intervention phases (ex. RHR_Recovery (during) - RHR_Recovery (pre-intervention)).

Group Test= A linear mixed model for RHR and PSS-4 with fixed effects for Week, Phase (0=pre, 1=post, 2=during) and a Week x Phase interaction, plus a random intercept for participant.

Sensitivity Analyses= Paired t-tests (Wilcoxon as nonparametric alternative).

Daily Sleep Duration (min) will be derived from nightly PPG wearable-recorded data. All primary endpoints are computed at the individual level and compared by week using week-level means (averaged from the individual daily scores). Sleep Duration [min] Individual Test= Like earlier mentioned tests these will include week-to-week differences for the weeks during the phase (Baseline Week, Study Week, Exam Week, Recovery Week) (ex. SleepDuration_Recovery (during) - Sleep Duration_Exam (during) and comparisons with pre/post intervention phases (ex. SleepDuration_Recovery (during) - SleepDuration_Recovery (pre-intervention)).

Group Test= A linear mixed model for Sleep Duration and PSS-4 with fixed effects for Week, Phase (0=pre, 1=post, 2=during) and a Week x Phase interaction, plus a random intercept for participant.

Sensitivity Analyses= Paired t-tests (Wilcoxon as nonparametric alternative).

Sleep Consistency will be measured as the standard deviation of nightly mid-sleep time derived from wearable-recorded sleep onset and offset times over each 7-day period, aggregated weekly at the individual level and compared across pre-intervention, intervention, and post-intervention phases. Sleep Consistency Individual Test= Like earlier mentioned tests these will include week-to-week differences for the weeks during the phase (Baseline Week, Study Week, Exam Week, Recovery Week) (ex. SleepConsistency_Recovery (during) - SleepConsistency_Exam (during) and comparisons with pre/post intervention phases (ex. SleepConsistency_Recovery (during) - SleepConsitency_Recovery (pre-intervention)).

Group Test= A linear mixed model for Sleep Consistency and PSS-4 with fixed effects for Week, Phase (0=pre, 1=post, 2=during) and a Week x Phase interaction, plus a random intercept for participant.

Sensitivity Analyses= Paired t-tests (Wilcoxon as nonparametric alternative).

Moderation by demographics (age, race, gender) on primary outcomes.