A Digital Mindfulness Intervention to Improve Sleep Efficiency and Heart Rate Variability in Healthy Adults

A Digital Mindfulness Intervention to Improve Sleep Efficiency and Heart Rate Variability in Healthy Adults: A Randomized Waitlist-Controlled Trial

This study tested whether a 10-day smartphone app-based mindfulness program can improve sleep and reduce physiological stress in healthy adults. Eighty-one healthy adults were randomly assigned to either a mindfulness group (completing a daily 10-minute guided session via the Ōura app for 10 days) or a waitlist control group. All participants wore an Ōura Ring throughout the study to objectively measure sleep and heart rate variability (HRV). Questionnaires on perceived stress, sleep quality, burnout, and mindfulness were completed before, immediately after, and four weeks after the intervention. The study was conducted at the University of Southern Denmark.

This randomized controlled trial (RCT) used a waitlist-controlled design to examine whether a 10-day smartphone app-based mindfulness program could improve sleep and reduce physiological stress markers in healthy adults. The study was embedded within a broader 4-month longitudinal cohort study (N=140); the RCT sub-study focused on participants in the low-stress stratum (Perceived Stress Scale [PSS-10] ≤13) at screening. Participants (n=81) were randomized in approximately a 3:2 ratio to either a mindfulness intervention group (n=49) or a waitlist control group (n=32). The mindfulness group completed one 10-minute guided audio session daily ("destress" module, narrated by Headspace) delivered via the Ōura app for 10 consecutive days in free-living conditions at a time of their own choosing. Compliance was monitored objectively via app-recorded session timestamps. The waitlist control group wore the Ōura Ring and completed all questionnaires identically without receiving any intervention. All participants wore an Ōura Ring Gen 3 throughout the study to objectively and continuously measure sleep architecture, sleep efficiency, and heart rate variability (HRV). Self-report questionnaires on perceived stress (Perceived Stress Scale; PSS-10), sleep quality (Pittsburgh Sleep Quality Index; PSQI), burnout (Copenhagen Burnout Inventory; CBI), and mindful attention (Mindful Attention Awareness Scale; MAAS) were administered before, immediately after, and four weeks after the 10-day intervention period. The study was conducted at the University of Southern Denmark, Odense, Denmark.

Inclusion Criteria:

• Adults aged 20-60 years
• Body mass index (BMI) in normal range (18.5-29.9 kg/m²)
• Low stress at screening (Perceived Stress Scale (PSS-10) score ≤13)
• Willingness to wear the Ōura Ring continuously throughout the study
• No current regular mindfulness practice (defined as >20 min/week)
• Ability to provide written informed consent
• Sufficient Danish or English language proficiency

Exclusion Criteria:

• Current regular mindfulness or meditation practice >20 min/week
• Self-reported diagnosis of cardiovascular or neurodegenerative disease
• Current diagnosis of anxiety or depressive disorder
• Use of psychotropic medications, hypnotics, or medications affecting heart rate variability (HRV) or sleep
• Pregnancy
• Shift work or highly irregular sleep schedules
• Concurrent participation in another mindfulness or behavioral sleep intervention