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Year : 2022  |  Volume : 70  |  Issue : 4  |  Page : 1702--1704

Exercise and Asana Yoga in Parkinson's Disease: A Critical Analysis of Evidence and Definition

PR Srijithesh, S Mythirayee 
 Department of Neurology, National Institute of Mental Health and Neuroscience, Bengaluru, Karnataka, India

Correspondence Address:
P R Srijithesh
Department of Neurology, NIMHANS, Bengaluru - 560 029, Karnataka

How to cite this article:
Srijithesh P R, Mythirayee S. Exercise and Asana Yoga in Parkinson's Disease: A Critical Analysis of Evidence and Definition.Neurol India 2022;70:1702-1704

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Srijithesh P R, Mythirayee S. Exercise and Asana Yoga in Parkinson's Disease: A Critical Analysis of Evidence and Definition. Neurol India [serial online] 2022 [cited 2022 Nov 30 ];70:1702-1704
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Mailankody et al.[1] article on Yoga in Parkinson's disease (PD) is an interesting reading. Authors should be congratulated for the exhaustive review of the subject.

Although the authors have displayed due attention in following the PRISMA guidelines in searching the literature, they have not combined the data in quantitative synthesis. Whereas it is a good practice in refraining from conducting a meta-analysis when there is high heterogeneity among the papers, it is a standard practice that the effect size and confidence interval of the outcomes of the individual studies are clearly stated. Of the seven studies mentioned in the results, six studies had a sample size less than 30. We expect these studies to be at high risk of bias and the margin of confidence interval to be wide. It is a well-known fact in evidence-based medicine that the results of small sample size pilot studies are highly unreliable and meta-analysis of these studies yields incorrect conclusions. Conclusions based on such studies have led to discordant results when large studies are published.[2],[3],[4] Most of the published small studies are likely to have the risk of publication bias as smaller studies with neutral results are mostly uncommunicated or unpublished.

In this context, we did a quantitative analysis of the studies reported in the review [Figure 1]. The results show that although there is no significant difference when yoga is compared with exercise (stretching and resistance training exercises), yoga showed a significant difference in the unified Parkinson's disease rating scale (UPDRS) when the control did not have exercise as part of the treatment regime. [Figure 1]c shows that when yoga was compared with exercise, the standard mean difference of anxiety scales showed a significant yet clinically modest difference in favor of yoga.{Figure 1}

From Table 1 of the review, except for Kwok et al.,[6] (2019) all the studies had a sample size less than 30 and three studies had a sample size of 20 or less. As per the American Academy of Neurology (AAN) classification of evidence schemes for therapeutic interventions, five of the seven studies listed get the class II level of evidence. However, it is apparent that assigning classes of evidence to the studies without mentioning the effect size and the CI (Tables 1 and 2 from the paper) will not convey the exact quality of the conclusion from the studies. It reflects on the unreliability of the AAN classification system that studies can be graded without reference to the sample size, effect size, and CI. By this standard, a study with a sample size of 2 would also get a class II status if the prescribed measures of quality (randomization, allocation concealment, masking, and completeness of follow-up) are followed.

The studies do not show a significant difference when yoga is compared with exercise. The results indicate that yoga may have a beneficial effect as an add-on treatment for PD only as much as appropriate physical exercises do. Indeed, a proper control for studies in yoga would be physical exercises with or without contemplative/mindfulness practices. Unless this is performed, we cannot state that yoga has any class-specific effect for the disease it is prescribed for. Rather, it would have a clinical effect similar to that demonstrated for physical exercises and contemplative/mindfulness practices.

The possibility of a 'sham Yoga' is not feasible only as long as the essential core of what constitutes yoga is not clearly defined. On the contrary, defined yoga practices such as Ashtanga Yoga, Iyengar Yoga, Yin Yoga, Vinyasa Yoga, and Bikram Yoga can have sham controls as the salient nature of the physical exercises and associated contemplative/mindfulness practices can be easily mirrored in controls. However, for this, the defining features of 'yoga' have to be clarified.

From the works of scholars such as Mark Singleton[7] and James Mallison,[8] we understand that what is described as yoga by popular account is not what is described in various classical texts including Patanjali's Yoga Sutra.[9] In Patanjali's Yoga Sutra,[9] asanas mean sitting postures which would enable the practitioner to be comfortable for meditative practices. Patanjali described yoga as 'silencing' of the stream of conscious thoughts.

Singleton reports that a literature survey of the holdings of the Cambridge University Library and the British Library in London revealed that prior to 1920s, the subjects of asana and hatha yoga was absent in primers. The modern school of asana yoga has its roots in the works of T Krishnamacharya and his disciplines. The widely popular Suryanamaskara has its origin in their works and not in the classical Hatha Yoga texts of the 11th–12th century. The Hatha Yoga ascetic practice of yoga, in turn, has its roots in the non-anatomical/non-physiological hypothesis of kundalini. Mallison and Singleton, in a review of the history of hatha yoga practises, note that the rationale of asanas such as sirsasana is to immerse the life energies of kundalani in the brain (rather than allow it disperse down) using the effect of gravity.[8] De Michelis classifies modern yoga practices as psychosomatic yoga (as propounded by Swami Vivekananda), denominational yoga such as Sahaja Yoga and transcendental meditation, postural yoga such as Iyengar Yoga and Asthangha Yoga and meditational yoga such as Vipassana and Chinmay yoga.[10] Singleton notes that Vivekananda makes an “emphatic distinction between the 'merely' physical exercises of Hatha Yoga and his description of yoga in his book “Raja Yoga”.

Although these issues of categorization are passingly mentioned by many apologists of yoga, its significance as the 'semantic slippage' (changing meaning such that variants do not resemble the originals in forms and substance) is not really documented.[7] This ambiguity of meaning is reflected in the paper which the authors cited (Mishra 2012)[11] while stating that yoga is a 'mind–body' intervention. We believe that the coinage 'mind–body' intervention needs more clarification.

Mishra et al.[11] conflates 'yoga' with many other terms used in different contexts such as Karma Yoga, Raja Yoga, and Jnana Yoga. The authors consider the above-mentioned terms identical, whereas in the article by Mailankody et al.[1] only Asana Yoga is considered. Mishra et al. state that the description of Yoga as a 'mind–body medicine' is given by the 'National Center for Complementary medicine'. Here, it is important to differentiate papers published in journals of alternative medicine with those published in regular academically peer-reviewed journals. The lack of technical clarity of terms in peer-reviewed journals would perpetuate the 'coinage' to regular uncritical usage by academic cross citation. We draw attention to the conflation of the term yoga in the article by Mishra et al.[11] to which the present paper, Mailankody et al.[1] cites.

The authors state that both exercise and yoga increase the level of the brain-derived neuropathic factor (BDNF) and dopamine. However, in the conclusion, the authors state, “based on the literature detailing the effects of Yoga in ANS, HPA axis BDNF, and dopamine, yoga has disease-modifying effects”. We would paraphrase the conclusion of the review to state that although both asana yoga and exercise have disease-modifying effects in PD, we cannot say that yoga has an 'exclusive effect' that is beyond its property as a physical exercise.

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Conflicts of interest

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