A Systematic Review
Manoj Sharma, MBBS, MCHES, PhD, Taj Haider, MPH, Partha P. Bose, DTCD, MD First Published July 18, 2012 Research Article
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The morbidity and mortality associated with asthma make it a worldwide health concern. Corticosteroid therapy is the most popular method to treat asthma, but yoga has been identified as an alternative therapy to expensive drugs. A systematic review of studies meeting the following criteria is presented: (a) be published in the English language; (b) included in CINAHL, Medline, or Alt HealthWatch; (c) between the years 1972 and 2012; (d) include yoga as an intervention; (e) use any quantitative study design; and (f) measures one of the following outcomes: forced expiratory volume in 1 second, peak expiratory flow rate, airway resistance, or Asthma Quality of Life Questionnaire score. Of the 15 studies systematically analyzed, 10 documented significant improvement because of yoga. Limitations include lack of a theory-based approach, self-reporting errors, and intervention adherence issues.
Keywords yoga, asthma, peak expiratory flow rate, forced expiratory volume, chronic lung disease, airway
Although it is estimated that only 5% of adults1 and 7% to 10% of children2 worldwide suffer from bronchial asthma, the morbidity and mortality associated with the condition is worsening.1 In the United States, US$6 billion is spent annually treating asthma. Asthma is a chronic lung disease caused by the contraction of smooth muscle surrounding the airways, making it difficult to breath and resulting in coughing and wheezing.2 Patients suffering from mild to moderate asthma using inhaled corticosteroids are continually increasing dosages to control their asthma.3 In addition, these medications are now being considered as factors influencing the increase in morbidity and mortality associated with the disease, making it imperative that a nonpharmacological alternative be found.1
In India, yoga is a widely used method for treating asthma but has yet to become a popular treatment in the Western world.4 Yoga could be a cost-efficient alternative or complementary therapy to inhaled steroid drugs as some studies have shown its positive impact on reducing medication dosage, frequency of attacks, and peak expiratory flow rate (PEFR).5 Considering yoga practice reduces the sympathetic nervous system through stretching, relaxation through meditation (dhyana), and deep breathing (pranayama), its impact on the smooth muscle obstructing airways during an asthma attack seems promising.6 However, there are currently few studies examining the benefits of yoga for patients suffering from asthma. The purpose of this review is to determine whether or not yoga could be an alternative or a complement to mainstream asthma therapy.
Questions being addressed in this review include the following: Is yoga efficacious alone, or in tandem with medication, to significantly alleviate asthma symptoms of subjects and is there sufficient data available to draw conclusions regarding the efficacy of yoga in treating asthma? Has yoga been shown to significantly improve subjects’ objective—peak expiratory flow rates, forced expiratory volume in 1 second, and airway resistance—and/or subjective—Asthma Quality of Life Questionnaire score—outcomes?
A systematic review of studies involving yoga interventions to treat asthma was the method used in this study. To be included in this study, the article had to meet the following criteria: (a) be published in the English language; (b) included in CINAHL, Medline, or Alt HealthWatch; (c) between January 1972 and March 2012 (last 40 years); (d) include any form of yoga as an intervention (with or without corticosteroid inhalation therapy); (e) use any quantitative study design; and (f) measure at least one of the following outcomes: forced expiratory volume in 1 second, peak expiratory flow rate, airway resistance, or Asthma Quality of Life Questionnaire score. Exclusion criteria were the following: (a) studies that did not implement a quantitative design, (b) did not sample asthmatic subjects, and (c) did not index in CINAHL, Medline, or Alt HealthWatch. Few studies concerned with yoga as an intervention for bronchial asthma exist; consequently, the published date criterion must be as open as possible and include a long time period. In addition, yoga has been used as a therapy for many ailments including anxiety, diabetes, and hypertension. Here, it was necessary to omit these studies by including asthma in the Boolean phrases.
Three phases of data review were conducted for this study (Figure 1). To identify studies meeting these criteria, Medline, Alt HealthWatch, and CINAHL database searches were performed for Phase I. Boolean terms used to identify studies meeting the criteria included “Yoga AND Asthma Intervention” or “Yoga AND Asthma Program.”
Figure 1. Flow chart depicting the 3-phase data extraction process.
Using the above terms/phrases, 33 articles were returned: from 17 from Medline, 2 from Alt HealthWatch, and 14 from CINAHL. Phase II included preliminary distillation of the articles by eliminating duplicates (n = 5), review/discussion articles (n = 10), and studies not incorporating yoga in the intervention (n = 1). Of the remaining articles (n=17), 2 did not incorporate at least one of the following outcome measures: forced expiratory volume in 1 second, peak expiratory flow rate, airway resistance, or Asthma Quality of Life Questionnaire score. The remaining articles (n = 15) satisfied the eligibility criteria.
As a result of the data extraction process, 15 articles were found satisfying the eligibility criteria. Table 1 summarizes the studies including the year of publication, authors, study design and sample size, age of participants, intervention modality and dosage, and the salient findings. The studies are arranged by year of publication in the ascending order.
Table 1. Summary of Interventions Exploring Yoga as Therapy for Asthma (N = 15)
Table 1. Summary of Interventions Exploring Yoga as Therapy for Asthma (N = 15)
Abbreviations: PEFR, peak expiratory flow rate; FEV, forced expiratory volume; PCLE, pink city lung exerciser.
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The purpose of this review was to determine the efficacy of yoga, with or without pharmacological therapy, to improve some of the outcomes associated with asthma (forced expiratory volume in 1 second, peak expiratory flow rate, airway resistance, or Asthma Quality of Life Questionnaire score). In addition, this study’s objective was to determine if yoga is a valid treatment option for those with mild to moderate asthma by analyzing studies published between 1972 and 2012. Few studies implementing yoga as part of an intervention to treat asthma were found (n = 15). Of the 15 studies analyzed, 7 were conducted in India, 4 were conducted in the United States, 2 were conducted in the United Kingdom, 1 was conducted in Australia, and 1 was conducted in Ethiopia. Considering asthma can be highly variable exacerbated by environmental conditions, infections, and occupational factors, it is important to include diverse studies to identify the efficacy of such a yoga intervention.13
Of the 15 studies systematically analyzed, 10 documented a significant change in one or more of the objective or subjective outcomes associated with asthma due to yoga alone or in tandem with other intervention components (diet modification, medication, journaling, etc).1,2,4–7,10,13–15 Many of these studies implemented an integrative approach to treating asthma as the triggers of this disease are multifaceted and complex. These include stress, diet, physical activity levels, and environmental influences.5 Because of this it was important that outcomes measured included a variety of factors. In addition, the study design could have an impact in determining whether or not yoga is a sound alternative as well.
Among the studies included in this review, 11 implemented a randomized control design,2,3,5–7,9,11–15 whereas 2 studies used a quasi-experimental approach,4,8 1 study used a pretest/posttest design,10 and 1 study was a self-controlled match design.1 Interventions instituting a randomized control design are considered the most robust as this type of design minimizes internal and external validity, employs a pretest and posttest design, uses a control group for comparison, and selects subjects for each group randomly. The quasi-experimental design is similar to a randomized control design, except it does not include randomizing the sample, meaning subjects are specifically selected for each group. This sometimes occurs when researchers intent is to match subjects between groups (by age or sex) or when random selection is not ethical.16 Pretest–posttest design, although the simplest, and less expensive than a randomized control trial, contains threats to the internal validity of the study, including history (external events between the pretest and posttest) and maturation (growth of the subjects).
Of the identified studies, 8 implemented pranayama (slow and fast breathing technique; 2 with a Pink City Lung Exerciser that mimicked the breathing technique), 5 implemented asanas (low-impact physical activity exercises), 1 implemented yoga with the use of transcendental meditation, 1 used yoga with naturopathy, 1 used Iyengar yoga, 1 used Sahaja Yoga (meditation of thoughtless awareness3), and 2 used unspecified yoga techniques. It is important to note that many of the studies implemented multiple yogic exercises.
It is not surprising that the majority of the studies incorporated pranayama in their intervention as it involves rhythmic breathing to improve oxygenated blood flow.16 The intent of pranayama is to eliminate physical and emotional stress through deep breathing known to reduce sympathetic activity,17 thus alleviating symptoms of asthma. Asanas have been described as more than just stretching as they include meditation in prolonged postures that focus the mind and purify the body. Sahaja yoga consists of a state of mental silence often taught by an experienced instructor to eliminate distraction and reach peak meditative state.3
The duration of identified studies in this review range from a 2-week intervention using a Pink City Lung Exerciser device to mimic pranayama breathing techniques to two 6-month interventions that allowed subjects to go largely unmonitored.5,12 Among the studies, the durations of the interventions were 6 months (n = 2), 4 months (n = 2), 3 months (n = 4), 2 months (n = 2), 40 days (n = 1), 1 month (n = 2), 21 days (n = 1), and 2 weeks (n = 1). To correctly gauge the efficacy of a yoga intervention on asthma, it can be recommended that the intervention must be at least 2 to 3 months long with regular and sustained practice of yoga.
Many of the interventions included allowing the subjects to practice yoga unmonitored, although many interventions implemented a training period with an instructor to ensure proper form. This means that the majority of the studies included self-reporting, making it difficult to determine if subjects followed the routine as directed. To combat this issue, 2 studies incorporated the use of journaling as a method to determine adherence and subjective benefit. One such study concluded that their intervention dosage of 20 minutes 3 times daily for 3 months, chosen for optimal asthmatic benefits, was difficult for subjects to adhere as evident from their journal entries.6 This could act as a disadvantage for studies testing the efficacy of yoga because either subjects are not adhering to optimal dosage levels to receive benefits or the dosage levels for benefits are too high. Further research into this area is necessary to determine yoga’s efficacy regarding asthma.
An additional disadvantage is the impossibility of knowing whether subjects were practicing yoga correctly without affecting the cost, time, and attrition rates of the study. To overcome this problem, the majority of the studies provided a 1- to 4-week yogic training course taught by an advanced instructor before the intervention. One study provided a CD-ROM for home practice after 2 training sessions.5 Two studies provided weekly classes in addition to the at-home portion of the intervention,6,14 whereas 2 studies implemented an inpatient intervention.1,10 For the inpatient interventions as well as the interventions providing supplemental training each week, the benefits of yoga were most evident (Table 1). Furthermore, the study that provided only a CD-ROM for 6 months of home training did not conclude with any significant objective outcome improvements (forced expiratory volume in 1 second, peak expiratory flow rate, or forced vital capacity). This suggests that training throughout the intervention, whether it be inpatient intervention or through classes, can be most efficacious. Determining the optimum training and follow-up training for subjects must be further assessed.
Of the studies identified, an additional disadvantage was the lack of use of a theoretical model in the planning of the intervention. Future interventions can use behavioral theories such as social cognitive theory, health belief model, theory of reasoned action, theory of planned behavior, or transtheoretical model in designing yoga interventions, which would be more efficacious.18
Although some disadvantages associated with yoga interventions have been identified, it is important to consider the advantages of using yoga for asthma. Yoga can reduce or eliminate the use of steroids, associated with an increased morbidity and mortality of asthma, as well as have the ability to decrease sympathetic nervous system activity that effects smooth muscle contraction around the airways.6 Considering the number of studies available testing yoga as a therapy for asthma are limited, more research must be done to determine the dosage most beneficial for asthma sufferers, the integrative approaches that work best in tandem with yoga, and the proper amount of training necessary for the most efficacious results.
MS conceptualized the study, developed the inclusion criteria, collected the data, developed the table, analyzed the data, and reviewed the article. TH collected the data, analyzed the data, and wrote the first draft of the article. PPB helped in selection of inclusion criteria, collected the data, analyzed the data, and reviewed the article.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
The authors received no financial support for the research, authorship, and/or publication of this article
This study did not warrant institutional review board review as no human subjects were involved.
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