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

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.

Slow Breathing at Six Breaths per Minute Improves Baroreflex Sensitivity and Reduces Blood Pressure

Key Points

• Slow breathing improves baroreflex sensitivity, reduces blood pressure, and potentially reduces chemosensitivity

• Slow breathing with ujjayi is not as effective as slow breathing alone in untrained practitioners

• Choose an inhale-to-exhale ratio that is comfortable for you when practicing slow breathing

The Breathing Diabetic Summary

Slow breathing at around 6 breaths/min improves cardiovascular and autonomic functioning. For example, it increases baroreflex sensitivity (BRS), which measures your heart’s ability to adjust your blood pressure in response to changing conditions. Slow breathing also increases parasympathetic tone, leading to better autonomic balance. This study assessed two additional aspects of slow breathing.

First, it evaluated the added effect of “ujjayi” breathing. Ujjayi breathing involves tightening of the throat during the inhale or exhale to make an ocean sound (check out the Wiki article for a simple explanation). It can be somewhat challenging to learn, but many trained yogis use it exclusively during their yoga practice. 

Second, this study examined how the ratio of inhale to exhale affected cardiovascular and autonomic outcomes. Extended exhales are regularly practiced for relaxation. For example, you perform a 4 sec inhale and 8 sec exhale. However, an equal ratio has also been proven to enhance heart rate variability (for example, 5 sec inhale, 5 sec exhale). Here, they assessed these different ratios to help establish the best approach for beginners to slow breathing.

Study Details

The study had seventeen participants. Measurements were taken in the supine position while the subjects breathed spontaneously for three minutes. Then, they performed the following breathing protocols: 

• Controlled breathing at 15 breaths/min 

• Controlled breathing at 6 breaths/min with 5 sec inhale and exhale

• Controlled breathing at 6 breaths/min with 3 sec inhale and 7 sec exhale

• Both 6 breaths/min protocols, but with ujjayi.  

The order of the slow breathing was selected randomly for each subject, and there was a two-minute break between each protocol.

Slow Breathing without Ujjayi is More Effective for BRS

The results showed that all of the slow breathing techniques improved BRS. However, there was no added benefit of ujjayi and it actually worsened BRS slightly when compared to slow breathing alone. 

Slow Breathing Reduces Blood Pressure

Interestingly, slow breathing increased heart rate, except when practiced with an equal inhale/exhale.  However, slow breathing reduced diastolic and systolic blood pressures. The decrease was most significant when an equivalent inhale/exhale was used. Again, slow breathing alone outperformed ujjayi.

Slow Breathing & Chemosensitivity

Lastly, they found that slow breathing decreased chemosensitivity. However, the measurement of chemosensitivity was heuristic: it was defined as the tidal volume divided by inhale time. That is, if your tidal volume increased for a given inhale time, that would indicate an increased chemosensitivity (because you are taking a bigger breath over the same inhale time).

Conversely, they also measured end-tidal CO2, and these results showed that all versions of slow breathing significantly reduced CO2 compared to spontaneous breathing. People often overcompensate for the slow breathing rate with bigger breaths, which appears to have happened here. Consistent training or biofeedback can reduce this over-breathing.

In any case, although they concluded that slow breathing reduced chemosensitivity, the significantly decreased end-tidal CO2 does not support this finding in my opinion.

Breathe at a Ratio that is Comfortable to You

To summarize, this study found that slow breathing increased BRS and reduced blood pressure. It also reduced their measure of chemosensitivity.  Although using an equal inhale to exhale ratio showed slightly better results, they suggest that “practitioners can engage in a ratio that is personally comfortable and achieve the same BRS benefit.” 

Interestingly, ujjayi worsened the results when compared to slow breathing alone. They hypothesize that the extra effort needed for ujjayi dampened the parasympathetic response. These results would likely be different in seasoned ujjayi practitioners. 

Therefore, we can conclude that slow breathing at a rate of 6 breaths/min improves cardiovascular and autonomic function. The best way to begin is to choose a ratio that is comfortable for you.

Abstract

Slow breathing increases cardiac-vagal baroreflex sensitivity (BRS), improves oxygen saturation, lowers blood pressure, and reduces anxiety. Within the yoga tradition slow breathing is often paired with a contraction of the glottis muscles. This resistance breath "ujjayi" is performed at various rates and ratios of inspiration/expiration. To test whether ujjayi had additional positive effects to slow breathing, we compared BRS and ventilatory control under different breathing patterns (equal/unequal inspiration/expiration at 6 breath/min, with/without ujjayi), in 17 yoga-naive young healthy participants. BRS increased with slow breathing techniques with or without expiratory ujjayi (P < 0.05 or higher) except with inspiratory + expiratory ujjayi. The maximal increase in BRS and decrease in blood pressure were found in slow breathing with equal inspiration and expiration. This corresponded with a significant improvement in oxygen saturation without increase in heart rate and ventilation. Ujjayi showed similar increase in oxygen saturation but slightly lesser improvement in baroreflex sensitivity with no change in blood pressure. The slow breathing with equal inspiration and expiration seems the best technique for improving baroreflex sensitivity in yoga-naive subjects. The effects of ujjayi seems dependent on increased intrathoracic pressure that requires greater effort than normal slow breathing.

Journal Reference:

Mason H, Vandoni M, Debarbieri G, Codrons E, Ugargol V, Bernardi L. Cardiovascular and Respiratory Effect of Yogic Slow Breathing in the Yoga Beginner: What is the Best Approach?  Evid Based Complement Alternat Med. 2013;2013:743504. doi: 10.1155/2013/743504.

Hypoxia has positive impacts on insulin and blood glucose levels while also increasing energy expenditure

Key Points

• Hypoxia positively impacts insulin and blood glucose while also increasing energy use

• Hypoxia and exercise combined reduce weight and blood pressure in obese patients

• The positive effects of hypoxia are dose-dependent

Breathing Blueprint Summary

I love review studies because they save us a lot of time.  Researchers go through all of the literature on a specific topic and consolidate everything into one place for us to read. I like to think of The Breathing Diabetic as a big review of all of the research on breathing, health, and well-being…

This paper reviewed the literature on the potential therapeutic benefits of hypoxia for obese individuals.  We know from other papers we have reviewed on hypoxia that there are many benefits for diabetics as well.  And, since diabetes and obesity often occur simultaneously, this review study is relevant for us.

One important point they make, which bears repeating, is that it is not feasible for us all to have access to high altitude.  We cannot simply move to the mountains, or somewhere close enough, to periodically expose ourselves to high altitude.  But, there are ways to experience some of the effects of altitude while at sea level.  The authors specifically mention masks and tents that can reduce the amount of inspired oxygen to simulate high altitude.  However, we cannot forget that breath holds also simulate high altitude and are available to us anytime, for free!

One of the key findings was that fasting blood glucose and insulin levels were reduced in animals following intermittent hypoxia.  Additionally, energy expenditure was increased in animals following hypoxic exposure.  Finally, hypoxia combined with exercise (what they called “active hypoxia”) decreased body weight and blood pressure in obese humans.

They also found contradictory results in some studies, which appeared to be due to the severity of the hypoxia protocol used (something we have reviewed previously). Thus, again we see that the benefits of hypoxia are dose-dependent.

Overall, the authors conclude that hypoxia could be beneficial for obese populations. However, the improvements in insulin, blood glucose, weight, and blood pressure shown here are further evidence that intermittent hypoxia (Principle 3) can benefit anyone looking to improve overall health and well-being.

Abstract From Paper

Normobaric hypoxic conditioning (HC) is defined as exposure to systemic and/or local hypoxia at rest (passive) or combined with exercise training (active). HC has been previously used by healthy and athletic populations to enhance their physical capacity and improve performance in the lead up to competition. Recently, HC has also been applied acutely (single exposure) and chronically (repeated exposure over several weeks) to overweight and obese populations with the intention of managing and potentially increasing cardio-metabolic health and weight loss. At present, it is unclear what the cardio-metabolic health and weight loss responses of obese populations are in response to passive and active HC. Exploration of potential benefits of exposure to both passive and active HC may provide pivotal findings for improving health and well being in these individuals. A systematic literature search for articles published between 2000 and 2017 was carried out. Studies investigating the effects of normobaric HC as a novel therapeutic approach to elicit improvements in the cardio-metabolic health and weight loss of obese populations were included. Studies investigated passive (n = 7; 5 animals, 2 humans), active (n = 4; all humans) and a combination of passive and active (n = 4; 3 animals, 1 human) HC to an inspired oxygen fraction (FIO2) between 4.8 and 15.0%, ranging between a single session and daily sessions per week, lasting from 5 days up to 8 mo. Passive HC led to reduced insulin concentrations (-37 to -22%) in obese animals and increased energy expenditure (+12 to +16%) in obese humans, whereas active HC lead to reductions in body weight (-4 to -2%) in obese animals and humans, and blood pressure (-8 to -3%) in obese humans compared with a matched workload in normoxic conditions. Inconclusive findings, however, exist in determining the impact of acute and chronic HC on markers such as triglycerides, cholesterol levels, and fitness capacity. Importantly, most of the studies that included animal models involved exposure to severe levels of hypoxia (FIO2 = 5.0%; simulated altitude >10,000 m) that are not suitable for human populations. Overall, normobaric HC demonstrated observable positive findings in relation to insulin and energy expenditure (passive), and body weight and blood pressure (active), which may improve the cardio-metabolic health and body weight management of obese populations. However, further evidence on responses of circulating biomarkers to both passive and active HC in humans is warranted.

Journal Reference:

Hobbins L, Hunter S, Gaoua N, Girard O. Normobaric hypoxic conditioning to maximize weight loss and ameliorate cardio-metabolic health in obese populations: a systematic review. Am J Physiol Regul Integr Comp Physiol. 2017;313:R251-R264.