pranayama

Meta-Analysis: Slow Breathing Reduces Systolic Blood Pressure by 5.62 mmHg

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Key Points

  • Diabetics are at an increased risk of hypertension and its negative cardiovascular outcomes

  • Slow breathing reduces systolic blood pressure by 5.62 mmHg and diastolic blood pressure by 2.67 mmHg

  • Slow breathing is a simple way to reduce blood pressure and potentially improve cardiovascular outcomes

The Breathing Diabetic Summary

Hypertension is a significant risk factor for cardiovascular disease, which is the leading cause of death in the U.S. For instance, if systolic blood pressure rises from 115 mmHg to 135 mmHg, your risk of cardiovascular disease doubles.

People with diabetes are also much more likely to develop hypertension. Anywhere from 40 to 80% of diabetics have hypertension, a somewhat somber statistic. Moreover, I am writing this in April 2020 during the COVID-19 pandemic. Studies are revealing that hypertension is correlated with more severe complications.

All of this is to say that reducing blood pressure is more important than ever. There are several medications and lifestyle changes available; however, compliance with these approaches are often low. Therefore, alternative therapies are needed. One such treatment is slow breathing.

 

Slow Breathing and Hypertension

Slow breathing has consistently been shown to reduce blood pressure. In particular, a device called RESPeRATE (which is FDA approved), which slowly reduces breathing rate down to below ten breaths per minute, has been examined extensively. The American Heart Association has even given device-guided slow breathing a “class IIA” rating for reducing blood pressure.  

This meta-analysis provides a concise yet comprehensive summary of studies that have examined slow breathing and hypertension. Their strict search criteria and thorough review of the available randomized controlled trials (RCTs) make this the most robust meta-analysis of slow breathing and blood pressure published to date. 

 

Study Inclusion and Strict Search Criteria

The authors searched several public databases (e.g., Web of Science, MEDLINE) since their inception until mid-2015. They used a combination of search terms like “hypertension OR prehypertension” and “slow breathing OR device-guided breathing” to identify papers relevant to the meta-analysis.

In the identified papers, slow breathing was defined as anything below ten breaths per minute. The subjects had to perform slow breathing at least three times a week for at least 5 minutes each session. They included studies of people with both hypertension and prehypertension. The follow-up period had to be at least 4 weeks and changes in blood pressure had to be reported. They excluded studies of healthy subjects without baseline hypertension or prehypertension

 

Selecting Relevant Studies and Publication Bias

The authors started with 1,984 studies, but only 17 met their criteria for inclusion in the meta-analysis. Although meta-analyses are some of my favorites, there are caveats that we need to mention for this one.

Of the 17 studies selected, five were abstracts only. Additionally, only two had slow breathing without a device. The other fifteen were device-guided slow breathing using the RESPeRATE, and the maker of the device sponsored six of these. Thus, there was a high risk of publication bias with these studies.

 

Slow Breathing Significantly Reduces Blood Pressure

Despite these limitations, the collective results were impressive. The average decrease in systolic blood pressure (SBP) across all seventeen studies was 5.62 mmHg. The two non-device slow breathing studies had an even more significant drop of 7.69 mmHg. For diastolic blood pressure, the mean decrease was 2.67 mmHg for the device-guided slow breathing.  

 

Longer Practice Leads to Better Results

They also examined how the intensity of the slow breathing practice affected results—the conclusion: the longer subjects practiced, the greater their reduction in blood pressure. For example, for slow breathing <100 min a week, the decrease in SBP was 3.01 mmHg, for 100-200 min, it was 6.44 mmHg, and for >200 min, it was 14.00 mmHg.  

 

Reduced Blood Pressure Reduces Risk of Death

The significance of these findings is that modest reductions in blood pressure lower the chances of strokes, coronary events, heart failure, cardiovascular deaths, and total deaths. This is especially important for diabetics who are at higher risk of developing hypertension and heart disease.

Moreover, the improvements from slow breathing were similar to those seen with antihypertensive medications. Those medications have been shown to improve long-term outcomes in hypertensive and prehypertensive patients. Therefore, slow breathing could potentially provide similar positive results if practiced consistently over a long period.

 

Slow Breathing is Free and Has No Side Effects

Finally, slow breathing is free, easy to perform, and does not have any side effects. Moreover, the blood-pressure-lowering effects of slow breathing are far-reaching. For example, slow breathing helps with stress, anxiety, and depression, all of which will also help reduce blood pressure.

 

A Recap of the Main Points 

In summary, slow breathing reduces systolic blood pressure by 5.62 mmHg and diastolic blood pressure by 2.67 mmHg. The more time you practice per week, the greater the blood pressure reductions.  Slow breathing also lowers blood pressure by helping with anxiety, stress, and depression. And by lowering your blood pressure, you reduce the risk of many cardiovascular problems, like stroke or heart disease.

To begin, try breathing at six breaths per minute (4 sec inhale, 6 sec exhale) for five minutes a day and see how you feel. 

 

Abstract

OBJECTIVES: Interest is increasing in nonpharmacological interventions to treat blood pressure in hypertensive and prehypertensive patients at low cardiac risk. This meta-analysis of randomized controlled trials assesses the impact of device-guided and non-device-guided (pranayama) slow breathing on blood pressure reduction in these patient populations.

METHODS: We searched PubMed, EMBASE, CINAHL, Cochrane CENTRAL, Cochrane Database of Systematic Reviews, Web of Science, BIOSIS (Biological Abstracts) Citation Index and Alt HealthWatch for studies meeting these inclusion criteria: randomized controlled trial or first phase of a randomized cross-over study; subjects with hypertension, prehypertension or on antihypertensive medication; intervention consisting of slow breathing at ≤10 breaths/minute for ≥5 min on ≥3 days/week; total intervention duration of ≥4 weeks; follow-up for ≥4 weeks; and a control group. Data were extracted by two authors independently, the Cochrane Risk of Bias Tool assessed bias risk, and data were pooled using the DerSimonian and Laird random effects model. Main outcomes included changes in systolic (SBP) and/or diastolic blood pressure (DBP), heart rate (HR), and/or decreased antihypertensive medication.

RESULTS: Of 103 citations eligible for full-text review, 17 studies were included in the meta-analysis. Overall, slow breathing decreased SBP by -5.62 mmHg [-7.86, -3.38] and DBP by -2.97 mmHg [-4.28, -1.66]. Heterogeneity was high for all analyses.

CONCLUSIONS: Slow breathing showed a modest reduction in blood pressure. It may be a reasonable first treatment for low-risk hypertensive and prehypertensive patients who are reluctant to start medication.

 

Journal Reference:

Chaddha A, Modaff D, Hooper-Lane C, Feldstein DA.  Device and non-device-guided slow breathing to reduce blood pressure: A systematic review and meta-analysis.  Complement Ther Med. 2019;45:179-184. doi: 10.1016/j.ctim.2019.03.005.

 

How slow breathing improves physiological and psychological well-being (hint: it might be in your nose)

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Key Points

  • Slow breathing increases heart rate variability, respiratory sinus arrhythmia, and alpha brain wave activity

  • These physiological changes lead to improved behavioral outcomes

  • The nose links slow breathing to these positive physiological and psychological outcomes

The Breathing Diabetic Summary

I think this paper wins “Best Title Ever” award!

This was a review study that pulled together all of the scientific literature on slow breathing and psychological/behavioral outcomes.  They were trying to answer the following question: What physiological changes are common to all slow breathing studies that have shown improvements in stress and anxiety?

After using some rather rigorous criteria for their literature search, they reduced 158 potential papers down to only 15. 

The physiological outcome parameters they focused on were heart rate variability (HRV), respiratory sinus arrhythmia (RSA), and brain wave activity.  The studies they examined also used several different subjective questionnaires to assess stress, anxiety, depression, and well-being.

As it is with science, there was a lot of nuance and many contradictory findings.  However, several common results did emerge.

First, slow breathing was associated with increases in HRV, particularly in the low frequency (LF) band.  Second, it was associated with increases in RSA.  Finally, slow breathing was associated with increases in alpha brain wave activity (brain waves associated with “flow”) and decreases in theta brain wave activity. 

All of these common physiological changes observed during/after slow breathing were associated with improved psychological and behavioral outcomes.  For example, several studies showed reductions in anxiety, improvements with depression, reduced anger, and increased relaxation.

Thus, slow breathing consistently increases HRV, RSA, and alpha brain wave activity.  These physiological changes then improve psychological and behavioral outcomes.

From a practical perspective, all of the studies used breathing rates of 3-6 breaths/min.  With practice, we can use an app (such as Breathing Zone) to achieve these rates.

Lastly, they examined the importance of the nose.  They reviewed studies showing that nasal breathing has a direct relationship with brain activity, which goes away when the nasal cavity tissue is numbed.  Moreover, certain areas of the brain follow oscillations that match breathing…but only with nasal respiration.  In fact, simply puffing air into the nostrils activates the brain at those “puff” oscillations (independent of actually breathing).

The authors hypothesize that the nose is the link between slow breathing, brain and autonomic functioning, and positive emotional outcomes.

From all of this, we find that slow breathing through the nose at 3-6 breaths/min (Principle 1) has positive effects on HRV, RSA, and brain wave activity.  These benefits then lead to improved psychological and behavioral outcomes.

Abstract

Background: The psycho-physiological changes in brain-body interaction observed in most of meditative and relaxing practices rely on voluntary slowing down of breath frequency. However, the identification of mechanisms linking breath control to its psychophysiological effects is still under debate. This systematic review is aimed at unveiling psychophysiological mechanisms underlying slow breathing techniques (<10 breaths/minute) and their effects on healthy subjects. Methods: A systematic search of MEDLINE and SCOPUS databases, using keywords related to both breathing techniques and to their psychophysiological outcomes, focusing on cardio-respiratory and central nervous system, has been conducted. From a pool of 2,461 abstracts only 15 articles met eligibility criteria and were included in the review. The present systematic review follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Results: The main effects of slow breathing techniques cover autonomic and central nervous systems activities as well as the psychological status. Slow breathing techniques promote autonomic changes increasing Heart Rate Variability and Respiratory Sinus Arrhythmia paralleled by Central Nervous System (CNS) activity modifications. EEG studies show an increase in alpha and a decrease in theta power. Anatomically, the only available fMRI study highlights increased activity in cortical (e.g., prefrontal, motor, and parietal cortices) and subcortical (e.g., pons, thalamus, sub-parabrachial nucleus, periaqueductal gray, and hypothalamus) structures. Psychological/behavioral outputs related to the abovementioned changes are increased comfort, relaxation, pleasantness, vigor and alertness, and reduced symptoms of arousal, anxiety, depression, anger, and confusion. Conclusions: Slow breathing techniques act enhancing autonomic, cerebral and psychological flexibility in a scenario of mutual interactions: we found evidence of links between parasympathetic activity (increased HRV and LF power), CNS activities (increased EEG alpha power and decreased EEG theta power) related to emotional control and psychological well-being in healthy subjects. Our hypothesis considers two different mechanisms for explaining psychophysiological changes induced by voluntary control of slow breathing: one is related to a voluntary regulation of internal bodily states (enteroception), the other is associated to the role of mechanoceptors within the nasal vault in translating slow breathing in a modulation of olfactory bulb activity, which in turn tunes the activity of the entire cortical mantle.

Journal Reference:

Zaccaro A, Piarulli A, Laurino M, et al.  How Breath-Control Can Change Your Life: A Systematic Review on Psycho Physiological Correlates of Slow Breathing.  Front Hum Neurosci.  2018;12:353.