Does Mindfulness Meditation Increase Heart Rate Variability?

This study showed mindfulness effects on nervous system control of the heart.

Reviewed by Monica Vilhauer

Key points

• HRV is increased when parasympathetic activity is increased.
• Effects of mindfulness on HRV were inconsistent, with some measures showing increased HRV and some no effect.
• Mindfulness also significantly reduced perceived stress and improved subjective sleep quality.

Heart rate variability (HRV) typically increases with parasympathetic activation (rest-and-digest response) and decreases with sympathetic activation (fight-or-flight response). The autonomic nervous system regulates various bodily functions, including respiration, where parasympathetic activity increases during exhalation and sympathetic activity rises during inhalation.

We'll now look at a study that aimed to examine the effects of mindfulness practice on HRV in a naturalistic setting, exploring both acute and chronic changes. The study also assessed how mindfulness affects respiratory rate. Mindfulness involves frequently refocusing attention on the present moment after distraction, which is thought to increase cognitive capacity and reduce stress, potentially leading to higher daytime and nighttime HRV. However, these cognitive effects of mindfulness remain speculative, and future studies are needed for further validation.

Intervention and hypotheses:
The researchers used the Headspace app to compare a 10-day mindfulness intervention with an active music listening control and a non-intervention control group. The primary outcome was HRV, measured through RMSSD (a time-domain measure of parasympathetic activity) and HF-HRV and LF/HF ratios (frequency-domain measures). The hypotheses were:

1. Mindfulness would increase daytime HRV after the intervention.
2. HRV would increase over the 10-day practice period.
3. Mindfulness would decrease respiratory rate in the acute phase but not in the chronic phase.
4. Mindfulness would increase HRV during sleep after the intervention.

Study design:
The study included 30 participants in each group: mindfulness, music control, and non-intervention control. Two-thirds of participants were female. Random assignment was used, but the researchers were not blinded to group allocation. Participants were excluded if they had prior mindfulness experience, psychiatric illness, or used certain medications. HRV was continuously measured for 48 hours before and after the intervention. The mindfulness group followed an introductory mindfulness course via the Headspace app, practicing for 20 minutes daily for the first 5 days and 30 minutes for the next 5 days. The music group listened to instrumental playlists for the same duration, while the control group maintained their usual routines.

Measures and findings:
HRV was measured through RMSSD (an indicator of parasympathetic activity), HF-HRV (related to respiratory sinus arrhythmia and parasympathetic activity), and the LF/HF ratio (indicating the balance between sympathetic and parasympathetic activity). Importantly, this mindfulness study did not involve intentional breath modulation, making it more reliable for assessing mindfulness effects independent of breathing regulation.

The study found:

• Mindfulness increased subjective mindfulness levels and reduced perceived stress, as shown by standardized questionnaires. Subjective self-rated sleep quality also improved in the mindfulness group.
• Mindfulness increased daytime RMSSD, but there were no significant changes in HF-HRV or the LF/HF ratio.
• Similarly, mindfulness increased nighttime RMSSD without significant changes in HF-HRV or the LF/HF ratio.
• No chronic effects on respiratory rate were observed in the mindfulness group.
• Both mindfulness and music produced acute increases in RMSSD, but only mindfulness significantly reduced respiratory rate during practice.

Discrepancy between RMSSD and HF-HRV:
The discrepancy between increased RMSSD and unchanged HF-HRV can be explained by the differences in what each metric captures. RMSSD reflects general parasympathetic activity and is less affected by respiratory patterns, while HF-HRV is more directly linked to breathing. In this study, the lack of intentional breath control could, one might speculate, explain why HF-HRV did not increase, even though RMSSD did. Thus, mindfulness may have increased general parasympathetic activity (as indicated by RMSSD) without significantly changing respiratory-driven vagal tone (measured by HF-HRV).

Correlations:
Adequate compliance with the interventions was verified, though there was some variability in adherence. There was a moderate positive correlation between the amount of mindfulness practiced and increases in RMSSD, suggesting that greater practice led to larger improvements in parasympathetic activity. Similar trends were observed in the music group.

Summary:
The results indicate that mindfulness may enhance HRV and reduce stress, but the findings were inconsistent across different HRV measures. Specifically, RMSSD increased while HF-HRV remained unchanged, possibly due to the study’s focus on non-breath-regulated mindfulness. Future research should explore whether long-term mindfulness practice produces sustained improvements in HRV and/or cognitive capacity. Limitations include potential differences in activity levels across groups — specifically the passive control group were just told to carry on with their lives as usual. Nonetheless, the findings suggest that mindfulness may positively influence HRV, especially when considering general parasympathetic activity.

This study summary also appears in audio format as part of the Mental health monologue of the week series on the Exploring Health and Medicine podcast.