Effect of slow breathing on autonomic tone & baroreflex sensitivity in yoga practitioners

Yoga Nidra for hypertension: A systematic review and meta-analysis

BACKGROUND

Hypertension is a prevalent chronic condition that affects a substantial proportion of the world's population. Medications are commonly prescribed for hypertension management, but non-pharmacological interventions like yoga are gaining popularity.

OBJECTIVE

The purpose of this systematic review and meta-analysis is to assess the efficacy of Yoga Nidra (YN) for the management of hypertension.

METHODS

A systematic review and meta-analysis of clinical trials, i.e., non-randomized and randomized controlled trials (RCTs) was conducted to investigate the effects of YN on hypertension. PubMed, the Cochrane Library, SCOPUS, and EBSCO were searched for relevant studies published up to September 2022. The quality of the included studies was assessed using the Cochrane risk of bias tool. The primary outcome measure was the change in systolic blood pressure (SBP) and diastolic blood pressure (DBP) after YN intervention, analyzed as weighted mean difference (WMD), in comparison to control groups. The random-effects model was used for the meta-analysis. Risk of bias was assessed for RCTs and non-RCTs using Cochrane's RoB-2 and ROBINS-I tools, respectively.

RESULTS

Five RCTs and three Non-RCTs involving a total of 482 participants (239 for YN vs 243 for controls) were included in this review. The meta-analysis indicated that YN significantly reduced SBP (WMD = 12.03 mm Hg, 95% CI [7.12, 16.93], Z = 4.80, p < 0.00001) and DBP (WMD = 6.32 mm Hg, 95% CI [3.53, 9.12], Z = 4.43, p < 0.00001) compared to control groups. The overall risk of bias for the three RCTs was high, whereas for the five non-RCTs, one had an overall moderate risk while the other four had an overall serious risk of bias.

DISCUSSION

This systematic review and meta-analysis provides evidence supporting the efficacy of YN as a complementary therapy for hypertension management. YN is a safe, cost-effective, and easily accessible intervention that primarily relies on interoception and induces a deep relaxation response in practitioners, aiding them in coping with various components of high blood pressure, such as stress, vascular inflammation, peripheral vascular resistance, etc. Our understanding of the mechanisms of YN is constantly evolving, and there is a need for further research to fully explore and appreciate the significance of this ancient science and its potential efficacy on BP. Considering the results and the multifactorial role of YN, it can act as a safe and reliable adjuvant therapy to complement the pharmacological treatment of hypertension. However, further studies with larger sample sizes, longer follow-up periods, and homogenous populations are warranted.

CONCLUSION

This meta-analysis suggests that YN is effective in reducing SBP and DBP, particularly in individuals with hypertension. The results highlight the potential of YN as a complementary therapy for hypertension management. Healthcare providers may consider recommending YN to patients with hypertension as an adjuvant therapy to medication. Further studies are required to identify standardized optimal forms and durations of YN best suited for hypertension management.

Role of yoga in stress management and implications in major depression disorder

Major Depressive Disorder (MDD) is one of the leading causes of disability affecting more than 340 million people and second largest contributor to global burden of disease. Chronic stress is a common risk factor and important contributor for MDD. Stress could be defined as the "perceived inability to cope". Stressful life events are shown to provoke a sequence of psychological and physiological adjustments including nervous, endocrine and immune mechanisms. Stress can lead to elevation of a variety of inflammatory cytokines and stress hormones, can cause autonomic dysfunction and imbalance in neurotransmitters. Yoga can reduce depressive symptoms by alleviating stress. Studies have shown that yoga can reduce inflammation, maintain autonomic balance and also has a role in maintaining the neurotransmitters. It has role on hypothalamic-pituitary-adrenal (HPA) axis, the peripheral nervous system including GABA, limbic system activity, inflammatory and endocrine responses. Yoga along with antidepressants can help in reducing the depressive symptoms in patient with MDD. Yoga is an ideal complementary and alternative therapy for mental health disorders.

Induced Relaxation Enhances the Cardiorespiratory Dynamics in COVID-19 Survivors

Most COVID-19 survivors report experiencing at least one persistent symptom after recovery, including sympathovagal imbalance. Relaxation techniques based on slow-paced breathing have proven to be beneficial for cardiovascular and respiratory dynamics in healthy subjects and patients with various diseases. Therefore, the present study aimed to explore the cardiorespiratory dynamics by linear and nonlinear analysis of photoplethysmographic and respiratory time series on COVID-19 survivors under a psychophysiological assessment that includes slow-paced breathing. We analyzed photoplethysmographic and respiratory signals of 49 COVID-19 survivors to assess breathing rate variability (BRV), pulse rate variability (PRV), and pulse-respiration quotient (PRQ) during a psychophysiological assessment. Additionally, a comorbidity-based analysis was conducted to evaluate group changes. Our results indicate that all BRV indices significantly differed when performing slow-paced breathing. Nonlinear parameters of PRV were more appropriate for identifying changes in breathing patterns than linear indices. Furthermore, the mean and standard deviation of PRQ exhibited a significant increase while sample and fuzzy entropies decreased during diaphragmatic breathing. Thus, our findings suggest that slow-paced breathing may improve the cardiorespiratory dynamics of COVID-19 survivors in the short term by enhancing cardiorespiratory coupling via increased vagal activity.

Slow yoga breathing improves mental load in working memory performance and cardiac activity among yoga practitioners

This study investigated the immediate effect of slow yoga breathing (SYB) at 6 breaths per minute (bpm) simultaneously on working memory performance and heart rate variability (HRV) in yoga practitioners. A total of 40 healthy male volunteers performed a working memory task, ‘n-back’, consisting of three levels of difficulty, 0-back, 1-back, and 2-back, separately, before and after three SYB sessions on different days. The SYB sessions included alternate nostril breathing (ANB), right nostril breathing (RNB), and breath awareness (BAW). Repeated measures analysis of variance showed a significant reduction in reaction time (ms) in 2-back condition immediately after ANB (−8%), RNB (−8%) and BAW (−5%) practices. Similarly, the accuracy was improved in the 0-back condition after RNB (4%), and in the 2-back condition after ANB (6%) and RNB (6%) practices. These results suggest that SYB practice enhances cognitive abilities (8–9%) related to memory load and improves the functioning of cardiac autonomic activity, which is required for the successful completion of mental tasks.Trial registered in the Clinical Trials Registry of India (CTRI/2018/01/011132).

The Cardiovascular Variability during Transient 6° Head Down Tilt and Slow Breathing in Yoga Experienced Healthy Individuals

OBJECTIVE

The intervention of yoga has been shown to improve autonomic conditioning in humans and better adaptability to orthostatic challenges. Similarly, slow breathing at 0.1 Hz akin to pranayama also increases baroreflex sensitivity (BRS). Hence, we intended to investigate whether yoga practitioners have different autonomic responses at rest,during slow deep breathingas well as during 6° head down tilt (HDT) compared to naive group individuals.

AIM

The aim of the study was to evaluate the acute effects of slow breathing on cardiovascular variability during HDT in yoga practitioners compared to yoga-naïve individuals.

SETTINGS AND DESIGN

This was a comparative study with repeated measures design conducted in Autonomic Function Test lab of the Department of Physiology, All India Institute of Medical Sciences, New Delhi, India.

MATERIALS AND METHODS

Time domain and frequency domain parameters of heart rate variability, blood pressure variability (BPV), and BRS were evaluated during 6° HDT and slow breathing at 0.1 Hz on forty yoga-naïve individuals and forty yoga practitioners with an average age of 31.08 ± 7.31 years and 29.93 ± 7.57 years, respectively. All of the participants were healthy.

STATISTICAL ANALYSIS USED

General Linear Mixed Model ANOVA was applied with yoga experience as a between-group factor in repeated measures. Independent sample t-test was applied for between group comparison of respiratory rate, demographic, and anthropometric data. P <0.05 is considered statistically significant.

RESULTS

Between-group comparison during HDT with spontaneous breathing has shown a significantly lower heart rate (P = 0.004) with higher RR interval (RRI) (P = 0.002) and pNN50% (P = 0.019) in yoga practitioners. The sequence BRS (P < 0.0001) and α low frequency (LF) of spectral BRS (P = 0.035) were also significantly higher in the yoga group compared to the naïve group. Similarly, during HDT with slow breathing, the heart rate was lower (P = 0.01); with higher RRI (P = 0.009); pNN50% (P = 0.048). Standard deviation of successive RR interval difference of systolic BPV was lower (P = 0.024) with higher sequence BRS (P = 0.001) and α LF of spectral BRS (P = 0.002) in yoga group than naïve group.

CONCLUSION

The yoga experienced individuals exhibit higher resting parasympathetic activity, lower systolic BPV, and higher BRS than naïve to yoga individuals. It is inferred from the findings that yoga practitioners were better adapted to transient cephalad fluid shift that happens during 6° HDT. Furthermore, acute slow breathing during 6° HDT reduced the systolic blood pressure in all the participants suggesting the beneficial role of slow breathing during exposure to extreme conditions such as microgravity which might help in the prevention of adverse effects of cephalad fluid shift during long-term weightlessness and maintain the astronaut health. Future mechanistic studies with active yoga intervention are necessary to understand the adaptive mechanisms involving central and vascular modulations contributing to either attenuation or accentuation of the cardiovagal baroreflex during HDT and slow breathing in healthy individuals.