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

March 10, 2026 updated by: University of Southern Denmark

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.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

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.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
91

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Denmark
      • Odense, Denmark, 5230
        • University of Southern Denmark. Department of Psychology.

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Description

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

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Mindfulness Intervention
Participants completed a 10-day app-based mindfulness program (one 10-min guided session/day via Ōura app) in free-living conditions.
Behavioral: App-based mindfulness program (Headspace via Ōura app)
Participants completed one 10-minute guided audio mindfulness 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 session timestamps.
No Intervention: Waitlist Control
Participants wore the Ōura Ring and completed all assessments without receiving any intervention.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Sleep Efficiency
Time Frame: Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Percentage of time asleep relative to total time in bed, measured continuously by Ōura Ring Gen 3 (accelerometry and photoplethysmography); computed as 7-day averages at each assessment timepoint.
Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Total Sleep Time
Time Frame: Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Minutes asleep per night, measured by Ōura Ring Gen 3.
Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Deep Sleep Duration
Time Frame: Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Minutes of slow-wave sleep per night, measured by Ōura Ring Gen 3.
Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Light Sleep Duration
Time Frame: Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Minutes of non-rapid eye movement (NREM) light sleep per night, measured by Ōura Ring Gen 3.
Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Sleep Onset Time
Time Frame: Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Clock time of sleep onset, measured by Ōura Ring Gen 3.
Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Heart Rate Variability (HRV)
Time Frame: Daily during 10-day intervention period
Root mean square of successive differences (RMSSD) (ms) measured during 10-min mindfulness sessions compared to an equivalent pre-session baseline period, assessed by Ōura Ring Gen 3.
Daily during 10-day intervention period
Perceived Stress Scale (PSS-10)
Time Frame: Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Perceived Stress Scale (PSS-10). Self-report questionnaire; sum score 0-40.
Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Pittsburgh Sleep Quality Index (PSQI)
Time Frame: Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Pittsburgh Sleep Quality Index (PSQI). Self-report questionnaire; global score 0-21.
Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Copenhagen Burnout Inventory (CBI)
Time Frame: Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Copenhagen Burnout Inventory (CBI). Self-report questionnaire; subscale scores 0-100%.
Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10); 4-week follow-up (Time 2: days 22-28 of follow-up)
Mindful Attention Awareness Scale (MAAS)
Time Frame: Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10)
Mindful Attention Awareness Scale (MAAS). Self-report questionnaire; sum score 15-90. Administered to the mindfulness intervention group only.
Pre-intervention (Time 0: 7-day average immediately before Day 1); post-intervention (Time 1: 7-day average immediately after Day 10)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
University of Southern Denmark

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Ulrich Kirk, PhD, University of Southern Denmark

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
December 1, 2023

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
May 1, 2024

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
August 1, 2024

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
March 3, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
March 10, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
March 13, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
March 13, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
March 10, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
March 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • 21345

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

De-identified individual participant data will be made available from the corresponding author (Ulrich Kirk; ukirk@health.sdu.dk) on reasonable request. Data sharing will comply with the Danish Data Protection Act and General Data Protection Regulation (GDPR) (Regulation EU 2016/679).

IPD Sharing Time Frame

Following publication of primary results

IPD Sharing Access Criteria

Data available upon reasonable request to the corresponding author.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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