Nowadays, yoga-meditation is endorsed and advised routinely to stay fit and healthy, as well as control many chronic diseases including diabetes type 2, hypertension, coronary artery diseases, etc. . Cortisol and β-endorphins are important biomarkers, which might be modified in the chronic diseases associated with stress . The interleukin (IL)-6 and tumor necrosis factor (TNF)-α are inflammatory cytokines that are involved in chronic diseases including diabetes, hypertension, dyslipidemia, and obesity that come under the umbrella of metabolic syndrome [3, 4, 5], respiratory diseases, as well as cancer . Previous studies have shown the efficacy of different lifestyle interventions in reducing stress and inflammation [7, 8, 9, 10, 11, 12, 13, 14, 15, 16], as well as physical well-being [17, 18]. Now, our assumption is that those who do regular yoga have different physiological persona than who do not do yoga regularly. Therefore, to test our hypothesis scientifically, the present study was planned to carry out the retrospective analysis to assess the persona differences by evaluating the baseline physiological characteristics and plasma levels of stress and inflammatory markers, cortisol, β-endorphin, interleukin (IL)-6 and tumor necrosis factor (TNF)-α, in long-term meditators vs. short-term male meditators vs. healthy controls.
Patients and methods
This retrospective analysis is based on our earlier study conducted at All India Institute of Medical Sciences (AIIMS), New Delhi, India, from October 2008 to December 2012. The analysis included three groups (n=97), all male subjects; long-term meditators, short-term meditators, and healthy controls. Fifteen apparently healthy long-term meditators (LTMs), practicing preksha meditation (since >5 years, at least 5 days a week) were included for the analysis; 58 subjects who attended one of our short-term yoga-based lifestyle intervention programs for 2 weeks at Integral Health Clinic, Department of Physiology, AIIMS, New Delhi were included as short-term meditators (STMs); and 24 age-matched subjects, who did not participate in any yoga programs, were recruited as healthy novice controls.
The study was conducted in accordance with the Declaration of Helsinki and was approved by the appropriate local ethics committee and Institutional Review Board. All subjects provided their consent. The trial was registered at Clinical Trial Registry India (CTRI), CTRI/2009/091/000727.
Estimation of biochemical markers
Fasting venous blood samples (5 mL) were collected (between 8:00 am to 10:00 am) in heparinized vials for the assessment of bio-markers, and samples processed as reported previously . The analysis was done using commercially available ELISA kits for plasma levels of cortisol (DRG Diagnostic, Germany), β-endorphin (Phoenix Pharmaceuticals, Inc., USA), TNF-α and IL-6 (Gen-Probe, Diaclone Diagnostic, France). Quality control assays were taken for the bio-markers, and the methods were validated.
SPSS version 20.0 (SPSS Software Inc., Chicago, IL, USA) was used for statistical analysis. Kruskal-Wallis Test applied followed by multiple comparisons using Mann-Whitney test with Bonferroni Correction (after Bonferroni correction p≤0.017) for the baseline assessment of body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), stress and immune markers comparison among LTMs vs. STMs vs. healthy controls. The comparison between baseline plasma cortisol levels and experience of yoga-meditation practice (weeks) was carried out using spearman’s rho correlation coefficient. The data is expressed as median (range) for nonparametric; and mean±SD for parametric data.
A total of 97 male subjects were included in the analysis. Significant baseline differences were observed for different physiological variables, with stress and inflammatory markers among LTMs vs. STMs vs. healthy controls. At baseline, body mass index (p=0.001), systolic blood pressure (p=0.016), plasma cortisol (p=0.001), interleukin (IL)-6 (p=0.001), and tumor necrosis factor (TNF)-α (p=0.001) were significantly lower whereas plasma β-endorphin (p=0.001) was significantly higher in LTMs compared to STMs and healthy controls (Table 1). In LTMs, baseline plasma cortisol levels were negatively correlated with the duration (weeks) of yoga-meditation experience (r=−0.709; p=0.02) (Figure 1).
STMs had significantly higher body mass index (p=0.016), systolic blood pressure (p=0.01), plasma cortisol (p=0.001), interleukin-6 (IL-6) (p=0.002) and tumor necrosis factor (TNF)-α (p=0.001) whereas plasma β-endorphin (p=0.002) was significantly lower compared to LTMs (Table 1). Also, body mass index (p=0.001) and plasma cortisol (p=0.002) levels were significantly higher in STMs compared to healthy controls (Table 1).
Present retrospective analysis observed significantly higher plasma β-endorphin and lower plasma cortisol, interleukin (IL)-6, tumor necrosis factor (TNF)-α, as well as body mass index and systolic blood pressure in LTMs compared to STMs. These results support that long-term, regular practice of yoga-meditation might modulate hypothalamic pituitary axis (HPA) as well as influence positively physiological parameters, body mass index and blood pressure. These LTMs were dedicated apparently healthy long-term yoga practitioners. On the other hand, the STMs included heterogeneous group comprising subjects with chronic diseases like diabetes type 2, hypertension, etc. as well as healthy subjects. The STMs had faith in yoga, and that’s why they enrolled themselves for one of our short-term yoga programs for 2 weeks. The STMs had higher levels of stress and inflammatory markers at baseline compared to healthy control group whereas the healthy control group had no experience of yoga-meditation (Novice group), still they had better stress and inflammation status than STMs. The possible explanation is that the two groups, STMs and healthy controls, were quite comparable regarding yoga practice as the data was at baseline. However, the heterogeneous STMs group included subjects with chronic diseases, and had intention to learn and practice yoga.
Present study showed decreased plasma cortisol levels with the duration of yoga-meditation experience which support the concept that yoga reduces stress, provides the substantial health benefits. These findings are consistent with the previous studies who observed the significant changes for the autonomic, inflammatory, and endocrine responses between expert yoga practitioners and novices [14, 19].
Previous studies have shown the impact of various relaxation techniques in the reduction of stress and inflammation [7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 20, 21, 22] with a plausible reason for stress reduction due to increased mindfulness; however, there may be several other complex activities in the brain that may combine to produce the relaxing effect. Present study also negatively correlated plasma cortisol levels with duration of yoga-meditation experience. Findings support the notion that hypothalamic pituitary axis (HPA) seems to be responsive to lifestyle interventions to reduce stress and this data is consistent with the previous studies [9, 10, 13, 14, 15, 16] showing practice of long-term yoga-meditation seems to be associated with improved emotional regulation.
A major limitation of the current study was that only male subjects were included for the analysis with limited number of subjects. Despite this, the results remain highly valuable as this study remains a unique study in Indian population that evaluated the physiological persona differences based on stress and inflammation among LTMs vs. STMs vs. healthy controls.
Our observations suggest that the subjects who do regular yoga-meditation practice have better stress & inflammation status than comparable age matched healthy controls.
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About the article
Published Online: 2019-12-24
Author Disclosure Statement: The authors have nothing to disclose.
Source of Funding: The authors are greatly thankful to the Department of Biotechnology (DBT, BT/PR10269/GBD/27/82/2007), New Delhi, for granting the financial support for successfully completing the study.
Conflict of Interest: There are no conflicts of interest.
Author Contributions: Dipti Magan: study conduct, acquiring data, analyzing and interpretation of data, and writing of the manuscript; Raj Kumar Yadav: study conceptualization, study design, data interpretation, and writing of the manuscript and approving the final content of the manuscript.
Clinical Trial Registry: The study was registered at Clinical Trial Registry India (CTRI), CTRI/2009/091/000727