Exploring the health benefits of bhramari pranayama (humming bee breathing): A comprehensive literature review

Sources and search strategy of literature

Our investigation of the literature was based on Scopus, PubMed, Cochrane Library and Google Scholar. In April 2023, the mentioned databases were searched using the search strategy ‘Keywords in title, abstract and keyword’ methodology. The search strategy was adapted to include terms relating to or describing a bhramari pranayama practice (i.e. Bhramari, Bhramari, Bee humming breath, Humming bee breath, Pranayama and Yoga breathing) as search words in the title or abstract or keywords. The electronic search strategy for PubMed was ‘(Bhramari[Title/Abstract]) OR (Bhramari[Title/Abstract]) OR (Bee humming breath*[Title/Abstract]) OR (Humming bee breath*[Title/Abstract]) OR (Pranayama[Title/Abstract]) OR (Yoga breathing[Title/Abstract])’. A similar searching strategy was adopted for Scopus, Cochrane Library and Google Scholar the first hundred results were identified based on the relevance. No limitations of years and restrictions of languages in the database were enforced during the search. In addition, reference lists of included papers were screened for additional eligible papers.

Eligibility criteria of literature

Studies had to meet the following eligibility criteria for study selection: (1) Study types: All experimental studies (which includes single-arm clinical trials, clinically controlled trials and randomised control trials [RCTs]) were considered eligible. On the other hand, conference abstracts, review papers, website articles, case studies, research protocols and publications without peered review were excluded. (2) Intervention types: Studies that included the individual effect of bhramari pranayama practice as an intervention were considered eligible. Studies were excluded if bhramari pranayama was not the intervention or it was combined with other practices. (3) Participant types: Studies conducted on healthy as well as unhealthy human patients with any age groups are eligible. (4) Outcomes types: Studies were eligible if they assessed any health-related outcomes related to any body system were considered eligible. Studies with no related results were excluded from the study.

Data extraction and management

The required pieces of information were extracted and verified. From each included study, the researchers have extracted the design of the study, country of affiliation, year of publications, characteristics of participants (sample size and demographic details of participants, age, gender, etc.), details of interventions, assessments and outcomes. The outcome variables assessed in each study were classified based on the health outcomes observed in the studies (i.e. psychological, cardiovascular, pulmonary variables or if any other health-related variables were found) and those extracted data were used in the required fields.

Characteristics of the included literature

The total number of studies included in this review was 46, including 18 single-arm clinical trials, 20 two clinically controlled trials (CCTs) and six RCTs that took place between 2006 and 2023. These 46 trials included a total of 3097 participants: six studies conducted only on males, three studies conducted only on females, 20 eight studies on both sexes and nine studies that did not specify the gender of the participants. The categorised age group of the participants showed that five studies were on adolescents (10–18 years), 31 studies were on adults (19–59 years), three studies were on senior adults (60 years and older), and seven studies did not mention the age group of the participants. The classified geographical regions showed that 38 studies were conducted from India, four studies were from Japan and one study each from Egypt, Nepal, Singapore and Spain. The mean total duration of intervention of the included studies was 10.04 ± 6.63 weeks as well as the mean duration of bhramari practice per day was 16.56 ± 12.88 min.

Twenty-four included studies conducted on bhramari pranayama were on psychological variables ^{[37,41,42,44,45,47,50,54-58,62,63,65,67,70,72,74,76,78-81]} followed by 22 studies were on cardiovascular variables^{[36-40,45,46,48,49,51,52,58,60,61,64,66-69,73,75,77]} and five studies were on pulmonary variables.^{[43,53,57,59,71]} The follow-up duration of bhramari pranayama was classified as very short-term (i.e. ≤1 week), short-term (i.e. one week to 3 months), intermediate-term (i.e. ≥ three months to 1 year) and long term (i.e. ≥12 months) showed 22 studies as very short term, 21 studies as short term, three studies as an intermediate-term and no studies showed it for long term. The graded health status of the participants showed that 31 studies were conducted on healthy populations and 15 studies were on patient population {i.e. four studies on hypertension,^{[48,49,51,52]} three studies on tinnitus^[40,55,76] and one study each on chronic rhinosinusitis,^[53] insomnia,^[56] visual impairment,^[54] menopausal syndrome,^[42] pregnancy,^[73] chronic obstructive pulmonary disease,^[43] asymptomatic COVID-19^[41] and dental patient).^[63] The details of each individual included study were presented in Table 1.

Effect of bhramari pranayama on psychological functions

This review included 24 trials on bhramari pranayama and psychological variables^{.[37,41,42,44,45,47,50,54-58,62,63,65,67,70,72,74,76,78-81]} There were ten single-arm clinical trials, 12 CCTs and two RCTs. Eleven studies were undertaken to examine the very short-term impacts of bhramari pranayama on psychological variables, while another 11 studies investigations were to observe the short-term impacts and two studies to examine the intermediate-term effects of the practise.

Gamma wave patterns were shown to be elevated during the practice of bhramari pranayama in a single-group clinical trial and in two clinical control trials of very short- and short-term duration.^[74,78,81] The findings also revealed that bhramari pranayama altered the scaling exponent for raw EEG data in frontal and temporal regions of the brain, symmetric activation in prefrontal regions and stronger temporal lobe synchrony.^[70,79,80] Bhramari pranayama practised for a short term resulted in a considerable rise in alpha-EEG after the practice, according to a single-group clinical investigation.^[67] Clinical controlled trials’ findings revealed significant improvement in attention performance following bhramari pranayama in a very short duration.^[37,47,54] Following the practise of bhramari pranayama, reaction time was also significantly shortened in the very short and intermediate intervals according to three studies, comprising a single-group clinical trial, a clinical control trial and an RCT.^[50,65,72] Bhramari pranayama practise was associated with lower levels of stress,^[41,44,45] anxiety^{[41,47,63,76]} and depression,^[41,76] according to single group clinical trials, clinically controlled trials and an RCT conducted for very short to intermediate periods. Following the practise of bhramari pranayama, single-group clinical trials and clinical controlled trials have shown a significant improvement in sleep quality,^[41,44,56] comfort levels,^[63] quality of life^[41,55] and overall mental health.^[42,62] Bhramari pranayama also had a considerable impact on the body’s prakriti (i.e. vata, pitta and kapha), according to two short-term clinical controlled trials.^[57,58]

Effect of bhramari pranayama on cardiovascular functions

This review included 22 trials on bhramari pranayama and cardiovascular variables.^{[36-40,45,46,48,49,51,52,58,60,61,64,66-69,73,75,77]} There were nine single-arm clinical trials, ten CCTs and three RCTs. Twelve studies were undertaken to examine the very short-term impacts of bhramari pranayama on cardiovascular variables, while another eight studies investigations were to observe the short-term impacts and two studies to examine the intermediate-term effects of the practise.

Single-group clinical trials, as well as clinical control trials with very short- to short-term follow-up periods, revealed increased heart rate, total peripheral resistant, diastolic blood pressure, and mean arterial pressure with a significant reduction in pulse interval, stroke volume and cardiac output during bhramari pranayama. Following the practice, there were significant drops in heart rate, pulse rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, rate-pressure product and double product.^{[38,39,40,46,51,52,64,68,77]} Four studies of short-term to intermediate-term duration, including three single group clinical trials and one RCT, showed a reduction in hyper-reactivity to cold pressor test after practicing bhramari pranayama.^{[45,66,73,75]} Short-term results from a clinical controlled trial indicated that bhramari pranayama increased cardiorespiratory endurance.^[58] In a short-term period, a single-group clinical trial revealed an increase in haemoglobin.^[67] The very short-term effects of bhramari pranayama on cerebral blood flow did not show any significant changes in the middle cerebral artery in the brain.^[61]

Single-group clinical trials, clinically controlled trials, and RCTs on heart rate variability performed for very short- to intermediate-term durations revealed a decrease in the RR interval, very low frequency (VLF) and high frequency (HF) as well as an increase in low frequency (LF) and LF to HF ratio during the practise of bhramari pranayama.^{[36,60,68,69]} Following the practise of bhramari pranayama, there was an increase in the RR interval, standard deviation of the N-N intervals (SDNN), root mean square of successive differences (RMSSD) and the number of adjacent NN intervals that differ from each other by more than 50 ms (NN50), percentage of successive RR intervals that differ by more than 50 ms (pNN50) and HF as well as decrease in the LF and LF to HF ratio.^{[37,38,39,48,49,69]}

Effect of bhramari pranayama on pulmonary functions

This review included five trials on bhramari pranayama and pulmonary variables.^{[43,53,57,59,71]} There were three CCTs and two RCTs. All five studies were undertaken to examine the short-term impacts of bhramari pranayama on pulmonary variables.

All lung function metrics increased significantly in a clinical controlled trial and RCTs conducted for short-term duration (i.e. increased in forced vital capacity, forced expiratory volume in 1 s, ratio of forced expiratory volume in 1 s and forced vital capacity, slow vital capacity, forced expiratory flow 25–75% and peak expiratory flow rate).^[57,59,71] A reduction in dyspnoea scores and sinonasal outcome scores was observed in short-term clinical controlled trials following the practice of bhramari pranayama in chronic rhinosinusitis and chronic obstructive pulmonary disease patients.^[43,53]

Effect of bhramari pranayama on patient population

This review included 15 trials on bhramari pranayama and patient population, including four studies on hypertension,^{[48,49,51,52]} three studies on tinnitus^[40,55,76] and one study each on chronic rhinosinusitis,^[53] insomnia,^[56] visual impairment,^[54] menopausal syndrome,^[42] pregnancy,^[73] chronic obstructive pulmonary disease,^[43] asymptomatic COVID-19^[41] and dental patient.^[63] Three studies were single-arm clinical trials, 11 studies were clinically controlled trials, and one study was RCT. Five studies were undertaken to examine the very short-term impacts, while another nine studies investigations were to observe the short-term impacts and one study to examine the intermediate-term effects of bhramari pranayama.

Clinical controlled trials and an RCT on hypertensive patients observed a significant decrease in systolic blood pressure, LF, and LF to HF ratio as well as an increase in RR interval, standard deviation of the N-N intervals (SDNN), root mean square of successive differences (RMSSD) and the number of adjacent NN intervals that differ from each other by more than 50 ms (NN50), percentage of successive RR intervals that differ by more than 50 ms (pNN50) and HF after the practice of bhramari pranayama in very short-term and intermediate-term period.^{[48,49,51,52]} The results of short-term clinical controlled trials on tinnitus patients showed that practising bhramari pranayama significantly reduced tinnitus annoyance, tinnitus loudness, tinnitus handicap, depression and anxiety associated with tinnitus and improved quality of life in tinnitus patients.^[40,55,76] Single-arm clinical trials and clinical controlled trials revealed improvement in sleep quality in insomnia patients,^[56] attention performance in visual impairment students^[54] and clinical symptoms in patients with menopausal syndrome.^[42] In asymptomatic COVID-19 patients and dental patients, bhramari pranayama practise reduced depression, anxiety and stress and improved sleep quality, comfort level and quality of life.^[41,63] Short-term single-arm clinical trials and clinical controlled trials have shown a reduction in the sinonasal outcome scores in patients with chronic rhinosinusitis,^[53] a reduction in dyspnoea scores in patients with the chronic obstructive pulmonary disease^[43] and a reduction in the cardiovascular hyper-reactivity to cold stress in pregnant women after practicing bhramari pranayama.^[73]

Adverse events

No adverse events or harmful effects were noted in any of the studies of bhramari pranayama included in our review.

Limitations

A limitation of this review is that the quality of the included studies was not assessed; nevertheless, it covered a wide range of clinical trials on bhramari pranayama and received a large number of citations, making it a valuable resource for individuals interested in research on this topic. To establish efficacy in a research setting, only RCTs and CCTs were considered robust study designs that minimise selection bias and distribute confounders. However, depending on the quality of the included research, the conclusions may or may not be stronger. It was not studied whether bhramari pranayama has any long-term effects during long-term follow-up, and fewer of the included research were designed as RCTs. A universal standardisation of bhramari pranayama practices throughout the research is necessary, as the practice guidelines and methodologies varied among the included studies.

Thus, more thorough RCTs with long-term follow-up are required in this area to determine whether bhramari pranayama practice will be advantageous in the long run. In addition, more RCTs are required in this field to confirm the practice’s efficacy in clinical conditions (such as tinnitus, hypertension, chronic obstructive pulmonary disease, chronic rhinosinusitis and insomnia). Future research could address these limitations and assess the mechanisms underlying the effects of bhramari pranayama in more clinical settings, especially within the field of experimental and cognitive psychology.