Written by Karen Pilkington and the CAM-Cancer Consortium.
Updated August 18, 2015

Yoga

Abstract and key points

  • Yoga is a practice consisting of physical exercises, breathing techniques, and meditation or relaxation.
  • It has small beneficial effects on quality of life and well-being of cancer patients.
  • It is generally safe when practised appropriately.

Yoga is a practice originating in India which usually consists of physical exercises (stretches orasanas), breathing techniques and meditation or relaxation. It is taught in yoga classes, can be practised by the individual or is incorporated into stress management programmes.

Yoga is claimed to have a range of physical, psychological and spiritual benefits.

Evidence from ten systematic reviews of small clinical trials mainly in breast cancer patients suggests yoga has small, short-term beneficial effects on quality of life, perceived stress and well-being. Evidence is conflicting, heterogeneous or non-significant for effects on other outcomes:

  • Anxiety: Positive short-term effects are reported but results are heterogeneous.
  • Depression: Positive short-term effects are reported but results are heterogeneous.
  • Distress: Reports of effects are mixed.
  • Fatigue: Positive effects are reported in more recent trials.
  • Perceived stress: Positive effects are seen on perceived stress in the short-term.
  • Physical health: Effects on physical health are not significant.
  • Quality of life: Positive effects are reported on quality of life.
  • Sleep problems: Effects on sleep are reported as non-significant.
  • Wellbeing: Positive effects are reported on various aspects of wellbeing.

Only a few small trials have involved patients with other types of cancer. Several recent trials suggest some effects on physiological measures related to inflammation and stress but these results are preliminary at best.

Few adverse events are reported in clinical trials and adverse effects appear to be rare, based on the limited number of case reports in the literature. Single case reports of serious adverse events indicate that these are possible, particularly with certain practices applied too aggressively or in people with specific risk factors.

What is it?

The word yoga derives from the Sanskrit root “yuj” which can be translated as to bind or yoke together or a 'union' and refers to the supposed union between mind, body and spirit.1 In its traditional form, yoga practice included moral disciplines in addition to physical exercises and meditation. The eight steps of Classical Yoga are yama or “restraint” or refraining from various vices, niyama or “observance” which includes contentment and tolerance, asana – the postures or physical exercises, pranayama – the breathing techniques, pratyahara which is the preparation of the mind for meditation, dharana –concentration, dhyana - meditation and samadhi or “absorption” - realization of the essential nature of the self.2 Different forms of yoga exist: in the West, the most widely practised form is Hatha yoga, which includes physical postures and exercises to stretch and improve flexibility of the body, breathing exercises, relaxation and meditation.3 Some of the more recently introduced forms of yoga include Iyengar, which is based on Hatha yoga but often makes use of props such as blocks in performing the asanas, Ashtanga or ‘power’ yoga, Vinyasa (‘flowing’ yoga) and Bikram (‘hot’ yoga performed in high temperatures and humidity).4

Application and dosage

Yoga is provided in classes led by a yoga teacher. It can also be practised by the individual having learnt the techniques in a class or from audio-visual resources such as DVDs or instruction books.

History/providers

Yoga originated in Indian culture and in its original form consisted of a complex system of spiritual, moral and physical practices aimed at attaining ‘self-awareness’.3 The ideas surrounding yoga practice were first introduced to the West in the 1890s by a Hindu teacher, Swami Vivekananda, who toured around Europe and the USA.1 Other Indian yoga practitioners followed and, in the 1960s, interest in Hindu spirituality increased. A series of case studies were reported which focused on aspects such as heart rate and blood pressure of yoga practitioners.5 These were followed by early trials of yoga in the control of hypertension.6,7 Psychological aspects of long-term yoga practice were also discussed.8 In the 1980s and 1990s, research published by Dean Ornish, a physician and professor at the University of California, generated further interest in yoga as a therapeutic intervention and component of a lifestyle intervention in heart disease.9,10 By 2004, trials were being conducted of yoga in a range of medical conditions.11 The popularity of yoga has continued to increase, with yoga classes widely available and offering a range of variations on the original practice.12

Claims of efficacy and alleged indications

Yoga is used by people suffering a range of health-related problems as well as to improve general fitness levels.12 Common uses include for the relief of stress, anxiety and depression, for chronic pain and as part of programmes such as mindfulness-based stress reduction used in cancer patients. It is widely promoted as beneficial to physical, psychological and spiritual health.

Mechanisms of action

In general terms, the asanas or stretches involve standing, bending, twisting and balancing the body leading to improved flexibility and strength. Breathing exercises and control help to focus the mind and achieve relaxation while the aim of meditation is to calm the mind.3 The exact mechanism of action is unclear although several theories have been proposed. These include modulation of the stress response systems with consequent reduction in sympathetic tone and catecholamine levels, and reduction in activation of the hypothalamic pituitary axis. It has also been suggested practice of yoga leads to activation of antagonistic neuromuscular systems increasing the relaxation response in the neuromuscular system.3 Meditation is thought to stimulate the limbic system and has been shown to increase blood flow to the brain and the release of endogenous dopamine, and to reduce respiratory rate. One study reported increased levels of GABA, a neurotransmitter, as a result of practising yoga asanas.13

Prevalence of use

Practice of yoga is increasing in prevalence, particularly in the Western world. By 1998, an estimated 15 million adults in the USA had used yoga at least once and over 7 million had used it within the previous year.12 Sixty four per cent used it for wellness and 48% for specific health problems. An increase in prevalence was also demonstrated between 2002 and 2007.14,15 With regard to practice in cancer patients, various figures have been reported: between 1 and 4 % of breast and gynaecological cancer patients in Europe 16,17, no reported use in other cancer patients such as lung and colorectal cancer 18,19 and up to 12 to 18% in cancer patients in the USA.20,21

Legal issues

There is no mandatory regulation of yoga teachers in countries including the USA, Australia and Europe. Regulation of yoga teachers is currently voluntary and is provided through a number of organisations including the Yoga Alliance in the USA and the International Yoga Federation. In the UK, the British Council for Yoga Therapy has worked with the Complementary and Natural Healthcare Council (CNHC) which provides a mechanism for voluntary regulation of yoga therapists.

Costs and expenditures

The cost of yoga classes varies widely with typical costs in Europe (based on costs advertised on the internet in March 2015 for classes in the UK and Germany) of between 5 to 15 Euros per hour.

Does it work?

Systematic reviews, meta-analyses

Ten systematic reviews of yoga in cancer have been published, 9 of which included between 6 and 18 randomised controlled trials (and a total of 313 to 905 patients).22-29, 37-38  The reviews are described in table 1. Differences in the number of included studies reflect differences in the inclusion criteria, whether trials were restricted to certain types of cancer and the range of outcomes covered. The date of the searches also affected the number of trials located. One recent review searched only for studies published between January 2010 and July 2012 and included a range of study types 29  while one, which focused solely on patients with haematological malignancies, included only one small trial.37

Breast cancer

Systematic reviews of yoga in breast cancer address a wide range of outcomes. These reviews demonstrate evidence of a significant but possibly short-term beneficial effect on quality of life and evidence of a small beneficial effect on well-being, with the evidence described as moderate to good for both outcomes.22,24,25,27,28 One systematic review concluded that the effect size for improved psychosocial outcomes was moderate to large.22 Conclusions on the evidence were conflicting with regard to the effects of yoga on sleep and psychological health while recent trials of fatigue have been more positive than older trials.22,23,24,26-28, 37. Effects on physical function were not found to be significant.22 The evidence also indicated that effects were limited to the active treatment phase.24 The quality of the included trials varied considerably. There is also potential for the introduction of bias particularly when subjective outcomes are assessed by patients as masking of treatment is impossible and selecting appropriate control interventions is difficult.

Haematological malignancies

A Cochrane review found only one small trial in 39 people with Hodgkin or non-Hodgkin's lymphoma. 38 This trial compared Tibetan yoga plus standard care against standard care alone. Beneficial effects on sleep were reported but the risk of bias was assessed as high.

Other cancers

Only three RCTs in patients with other types of cancer were included in the systematic reviews, one small trial in lymphoma patients as described above and two in mixed cancer types. In the two trials in mixed cancer, yoga was part of a mindfulness programme.25

Summary of effects by outcome (see Table 3)

Anxiety: Positive effects are reported on anxiety but results are heterogeneous and only positive in the short-term when yoga is compared with active controls rather than no treatment.

Depression: Positive effects are seen in depression in the short-term but results are heterogeneous.

Distress: Reports of effects on distress are mixed with more positive results reported when yoga is compared with active controls than no treatment controls.

Fatigue: Recent trials have reported more positive results than older studies leading to overall positive effects being reported for fatigue.

Perceived stress: Positive effects are seen on perceived stress in the short-term but not the long-term.

Physical health: Significant effects on physical health are not reported.

Quality of life: Overall, effects in quality of life are positive.

Sleep problems: Few trials have reported effects on sleep leading to overall non-significant results although positive effects are reported in one trial in lymphoma patients.

Wellbeing: Positive effects are reported on various aspects of wellbeing except in mental wellbeing when yoga is compared against no treatment.

Randomised controlled trials

Eight RCTs have been published since the most recent systematic review (see table 2).39-46 Of these, 7 were in breast cancer patients 39-44, 46 and one included mainly breast cancer patients. 45 A range of outcomes have been assessed including psychological responses, physiological markers of stress and inflammation, effects on lymphoedema and impact on overall quality of life. While some trials used appropriate methods for randomisation and allocation concealment, reducing bias to some extent, blinding of patients is not possible with interventions such as yoga. In most cases the control group received no treatment so there is no control for non-specific effects but there is some support for positive results from effects observed on physiological measures. However, interpretation of the results is complicated by varied interventions and differences in delivery (through classes, home practice and a combination of both of these). A further issue affecting implications for practice is that high attrition from yoga groups is a problem.

Is it safe?

Adverse events

Few adverse effects were reported in the clinical trials but participants do undergo screening prior to participation and, in the breast cancer trials, all participants were below 63 years of age.25

Several case reports of adverse psychological effects have been published but these appear to be related specifically to meditation.30 Other single case reports indicate that serious adverse events are possible, particularly with certain practices applied too aggressively. For example, spontaneous pneumothorax was observed in a patient following practice of Kapalabhati pranayama, a common breathing exercise.31 Certain postures such as headstands and the lotus position have also been associated reports of adverse effects in individuals. For example, sciatic nerve damage in a 67 year old woman,32 damage to a knee ligament when attempting an advanced stretch 33, eye-related problems in individuals with existing risk factors, for example a patient with glaucoma practising headstands34 and headstands linked to spinal compression in a patient with myelomalacia, a spinal condition. 47 Adverse events do appear to be rare based on the limited number of case reports in the literature. However, there is a lack of systematic evaluation so that adverse events may be underreported and any risks are difficult to assess. The reported cases indicate that certain practices may be not be advisable in individuals with existing risk factors.

Contraindications and warnings

Caution, including avoidance of specific postures such as inverted postures, has been suggested in pregnancy and in individuals with hypertension, although this appears to be based on likely risk.35,36 It has also been suggested that breathing exercises particularly if vigorous could potentially exacerbate asthma and other respiratory problems. Again this is based on theoretical risk and occasional case reports such as those above. Other conditions may require caution or the avoidance of specific practices and the advice of the primary healthcare professional and the yoga instructor prior to undertaking yoga.

Interactions

None known.

Evidence tables

Please view the PDFs listed below for details of the systematic reviews and/or controlled clinical trials included in this summary.

Table 1: systematic reviews of yoga for cancer

Table 2: controlled clinical trials of yoga for cancer

Table 3: effect sizes of yoga for various outcomes

Citation

Karen Pilkington, CAM-Cancer Consortium. Yoga [online document]. http://cam-cancer.org/The-Summaries/Mind-body-interventions/Yoga. August 18, 2015.

Document history

Fully revised and updated in August 2015 by Karen Pilkington.

Summary first published in June 2013, authored by Karen Pilkington.

References

 

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