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Abstract
Background: Hypertension is a growing public health problem and its optimal management is imperative. Integration of lifestyle modification and yoga with antihypertensive drugs leads to its successful management. Yoga has been shown to modulate blood pressure (BP) and lipid metabolism in individuals with hypertension. The current study is a preliminary effort to ascertain the underlying mechanisms behind it. Materials and Methods: Hundred patients were screened, among which 65 who met the inclusion criteria were recruited. After baseline assessments, they were randomly allocated (1:1) to an intervention group (IG) who practiced integrated approach to yoga therapy (IAYT)-based yoga module for 6 days a week, for 3 months and a control group (CG) who received no intervention. BP, heart rate variability, and lipid profile were assessed before and after the intervention. Data acquired from 60 cases were analyzed by post-hoc analysis for multiple comparisons between the mean values. Results: At the end of 3 months, within-group comparison showed significant changes (P < 0.05) in IG in all variables except triglycerides, high-density lipoprotein (HDL), and very low-density lipoprotein (LDL) while similar changes were not present in the control group. Significant differences were seen between the groups in the TC (P = 0.005), HDL (P = 0.047), non-HDL (P = 0.013), LDL (P < 0.001), LDL/HDL Ratio (P = 0.031), CHOL/HDL Ratio (P = 0.043), DBP (P < 0.001), SBP (P < 0.001), and all indices of HRV (P < 0.001). Conclusion: These findings suggest that IAYT-based yoga module was effective in improving cardiovascular performance and lipid metabolism, thereby mitigating coronary artery disease risk.
Keywords: Hypertension, integrated approach to yoga therapy, lifestyle modification, lipid profile, yoga
How to cite this article: Introduction 
Hypertension has become a common disorder in recent times.[1] It is a growing public health concern, with almost one in three Indian adults affected.[2] The World Health Organization has estimated that by 2025, 1.56 billion individuals will have hypertension, which is an increase of 60% from 2000.[3]
Global Burden of Disease study reported that hypertension has led to 17.9% and 34.6% of the population attributable risk for coronary artery disease (CAD) and stroke, respectively.[4] High blood pressure (BP) is the single largest contributor to the global burden of disease and mortality, making it imperative to optimize its prevention and management.[5]
The level of BP control is fairly low in the Indian hypertensive population, with just one-tenth of rural and one-fifth of the urban population having their BP under control.[6] Even hypertensive patients with optimum levels of BP are still at higher risk of CAD mortality than normotensive individuals.[7]
BP thresholds cannot be the only etiology for hypertension, as it has complex and interrelated causes. The main cause is the interrelation between genetic and environmental factors. Smoking, consumption of alcohol, less physical activity, excessive sodium and fat intake, lack of potassium, and fiber in diet and stress are some of the environmental risks.[8] Abnormalities in cardiac, renal, vasculature, and brain are associated with disease progression.[9] A growing body of evidence also suggests the existence of a clinical relationship between hypertension and dyslipidemia through genetic associations.[10]
Guidelines for the management of hypertension encourage anti-hypertensive drugs to be accompanied by the use of lifestyle modifications, including patient education, weight reduction, physical activity, low salt intake, smoking, and alcohol cessation, as well as non-pharmacological interventions such as yoga and meditation.[11],[12] Likewise, treatment of hypertension should also include the management of other CAD risk factors such as cigarette smoking, diabetes, lipid abnormalities, and comorbid conditions.[13]
Complementary and alternate systems of medicine are known to be beneficial in not only the management of hypertension but also its associated risk factors and comorbidities due to their holistic approach.[14],[15]
Yoga is a mind-body practice that operates at five levels of an individual's existence termed panca kosas. The Integrated Approach to Yoga Therapy (IAYT) includes asanas, pranayama, Bhavana (guided imagery technique), Dhyana, Yoga Nidra (deep relaxation), Mantra (chanting), and Yantra (Mandala drawing). All these practices are balanced to complete the Pañcakoça viveka, which eventually results in sound mind and body.[16]
The IAYT intervention is a comprehensive lifestyle modification program that is shown to be safe and effective in the management of hypertension.[17]
However, previous studies have not established the molecular mechanisms behind these physiological effects. Therefore, the present study was undertaken to evaluate the effect of an IAYT-based yoga intervention on cardiovascular functions and lipid profile, an associated risk factor for CAD in hypertensive patients. Preliminary efforts have also been made to find evidence for the mechanism underlying yoga intervention influencing lipid metabolism and cardiovascular function.
Materials and Methods The study was carried out as a single-center, randomized controlled trial. The study was conducted adhering to the tenets of the Helsinki Declaration,[18] and the report was written in accordance with the CONSORT 2010 Guidelines.[19] Before the commencement of patient recruitment, approval was obtained from the Institutional Ethics Committee (Vide Registration No: EC-169).
Participants
Participants were recruited using advertisements in the local press and by conducting a door-to-door survey in a 20 km radius of the study center. Patients who met the inclusion criteria and came forward were recruited. Before completing a consent form to express their agreement to participate, they were given thorough written and verbal information about the study.
Inclusion criteria
To be included in the study, patients had to be at least 18 years old and satisfy the criteria for diagnosis of hypertension according to the seventh report of the Joint National Committee on prevention, detection, evaluation, and treatment of high BP, published by the American College of Cardiology/American Heart Association.[20]
Patients with primary arterial hypertension (>130 mmHg systolic and/or >80 mmHg diastolic BP) were included in the study. They had to be receiving antihypertensive medication from their primary care physician at the time of the investigation. Furthermore, they had to agree to the following conditions:
No alteration of their antihypertensive medication in the next 3 monthsParticipation in the 10 days of intensive yoga training sessions in the study programAdditional unsupervised yoga sessions at home.Exclusion criteria
Secondary hypertensionSevere psychiatric comorbidities (major depression, dependency disorders, or psychosis)Coronary heart disease, myocardial infarction, pulmonary embolism, or stroke in the previous 3 monthsHeart failure of NYHA stage = IPeripheral arterial occlusive disease of stage = 1Renal failure of stage >2 with glomerular filtration rate <60 mL/min/1.73 m2Participation in any other clinical studies at the time of commencement of our trial or planned participation in such studies in the next 12 weeksPracticed yoga for 30 days or more in the previous 6 monthsPregnancy or breastfeeding.Design
One hundred participants were screened for eligibility criteria. Sixty five of them who met the inclusion criteria were recruited for the study. Five members dropped out from the study, three from the intervention group (IG) and two from the control group. The reasons for the subjects to discontinue from the study in the IG were, affected from COVID and viral fever and other one could not make up to postintervention assessment. In the control group, two were not able to come for post assessment [Figure 1].
The sample size was not calculated a priori; however, post-hoc analysis revealed that the study had adequate power (88.8%) to detect statistical significance.
Baseline assessments were conducted, after which the participants were randomly allocated to either IG or the control group in a 1:1 ratio. Block randomization technique with varying block lengths was used for this purpose. Randomization was done by a lab technician who was not involved in patient recruitment or assessment using a computer-based random number generator software[21] and prepared sequentially numbered closed envelopes. The study physician opened the envelopes after each participant's recruitment to reveal their group assignment.
Intervention
Integrated approach to yoga therapy group
The participants belonging to the IG were trained in the 1-h IAYT-based module for 10 days. The yoga training was administered by qualified and experienced yoga instructors who were asked to adhere to the module as closely as possible [Table 1]. It was stressed by the instructors that patients should focus on their breathing patterns as well as be aware of their body during asana practices. The module was specifically designed a priori in a consensus process by two certified yoga physicians with long-standing clinical experience. After this intensive phase of training, participants were asked to continue the practice for 1-h a day, 6 days a week for 3 months. They were monitored by phone calls during their home practice.
Table 1: Integrated approach to yoga therapy based on yoga module for hypertension (1-h)Control group
Participants in the control group did not receive any intervention. They went about their normal daily routine. In addition, patients in this group were asked not to initiate any yoga or exercise regimen during the study period. At the end of 3 months, they were offered the same yoga program as the IAYT group.
Outcome measures
Blood pressure
Clinical and laboratory variables were evaluated by a physician who was blind to the participant allocation. Both systolic and diastolic BP were recorded using a mercury sphygmomanometer. All BP measurements were recorded by the same physician.
Heart rate variability
The HRV was recorded for 10 min pre- and postintervention.
The ECG was recorded using a standard bipolar limb lead II configuration, which was digitized using an 8-bit analog-to-digital converter at a sampling rate of 1 kHz and was analyzed offline to obtain the HRV spectrum. Frequency domain and time domain analysis of HRV data were carried out using Lab Chart 8 (AD instruments, Australia) program, which uses the Lomb–Scargle Periodogram algorithm.
Lipid profile
Under aseptic conditions, 4 mL blood sample was collected 8 h after the last meal in a sterile vacutainer by venepuncture. The serum total lipid profile, including total cholesterol (TC), High-density lipoprotein cholesterol (HDL), and triglycerides (TGs) – by enzymatic methods, low-density lipoprotein cholesterol (LDL-C) – by the direct method were estimated.
Statistical analysis
The normality of the data was tested via the ShapiroWilk test. Mann–Whitney U-test and Wilcoxon signed ranked t-test were applied for data analysis as the data were not normally distributed. All statistical analysis was conducted using The Statistical Package for the Social Sciences (IBM Statistical Package for the Social Sciences (SPSS) for Windows, Version 21.0. Chicago, SPSS Inc).
Results There were no statistically significant differences in the demographic characteristics between the two groups [Table 2].
A comparison of the baseline data between the intervention and control group showed no statistically significant differences. Within group comparison in the IG showed a significant decrease in TC (P < 0.001), non-HDL cholesterol (P < 0.001), LDL cholesterol (P < 0.001), LDL/HDL Ratio (P = 0.01), CHOL/HDL Ratio (P = 0.004), diastolic BP (P < 0.001), Systolic BP (P < 0.001), mean heart rate (P < 0.001), low frequency (LF) band of HRV (P < 0.001) and LF/high frequency (HF) ratio (P < 0.001) and a significant increase in NN50 (P < 0.003), pNN50 (P < 0.001) and HF band of HRV (P < 0.001).
Within-group comparison in the control group showed a significant decrease in Mean Heart Rate (P = 0.001), NN50 (P = 0.001), pNN50 (P = 0.016), LF/HF ratio (P = 0.001), and a significant increase in HF band of HRV (P = 0.02).
Between-group comparison revealed a significant difference in the TC levels (P = 0.005), HDL cholesterol (P = 0.047), non-HDL cholesterol (P = 0.013), LDL cholesterol (P < 0.001), LDL/HDL ratio (P = 0.031), CHOL/HDL ratio (P = 0.043), diastolic BP (P < 0.001), systolic BP (P < 0.001), mean heart rate (P < 0.001), RMSSD (P = 0.017), NN50 (P < 0.001), pNN50 (P < 0.001), LF band of HRV (P < 0.001), HF band of HRV (P < 0.001), and LF/HF ratio (P < 0.001) [Table 3].
Table 3: Comparison of the data within and between the intervention group and control groupThere were no adverse events associated with the practice of yoga, in the IG.
Discussion The present study investigated the effects of an IAYT-based yoga module on the cardiovascular parameters and risk factors in middle-aged hypertensive individuals (49.48 ± 7.93). The results show that regular practice of an integrated yoga module improved lipid profiles, BP, and heart rate variability, as well as enhanced cardiovascular performance in hypertensives. These results are consistent with previous studies on the effect of yoga on lipid profile, BP, and heart rate variability.[22],[23],[24],[25],[26] However, none of the prior studies investigated the potential molecular pathways through which yoga may benefit hypertensives, as the current study did.
Hypertension has been linked with impaired cell membrane microviscosity.[27] This may result in alterations in membrane lipid composition as a result of extensive interchange between circulating and membrane lipids, as well as faulty cellular lipid production and metabolism.[28] Such lipid-dependent changes in membrane characteristics in cells involved in cardiovascular control might be part of the pathogenetic pathways causing persistent BP elevation.[29],[30] As a result, we sought to determine the molecular mechanism of action of yoga in regulating chronic BP increase via modulating lipid metabolism.
In the current study, reduction in LDL cholesterol, TG, and increase in HDL-cholesterol seen in IG at the end of 3 months, could be due to hydrolysis of TG-rich lipoproteins that simultaneously replace intramuscular fat used during pranayama and yogic practices. Yoga postures or asanas are a form of aerobic physical activity which lead to weight loss and changes in body composition. Reduction in body weight leads to an increase in adipose lipoprotein lipase activity, which breaks down circulating TG into fatty acids and glycerol by hydrolysis. This also upregulates Apo-AI, which is a major structural and functional component of HDL.[31] Sahay observed a significant reduction in BP and cholesterol, FFA, LDL, and very LDL cholesterol, and an increase in HDL cholesterol after 6 months of Yoga.[32] In a previous study, similar results were observed following 30 days of yoga and pranayama practice.[33] In the current study as well, normalization of lipid metabolism is associated with a significant reduction in both systolic and diastolic BP. Thus, normalizing the impaired lipid metabolism could be one of the mechanisms by which yoga helps in the management of hypertension.
There was a significant decrease in the Mean HR, LF, and LF/HF ratio of HRV, indicating decreased sympathetic activity. A significant increase in the RMSSD and pNN50 component of HRV was observed, indicating an increase in the vagal tone. There was also an increase in the HF component of HRV, thus, indicating an overall shift toward parasympathetic predominance. The pranayama component of the IAYT-based yoga module could have played a major role in improving both sympathetic and parasympathetic reactivity.[34]
BP and heart rate variability are strong indicators to measure cardiovascular performance. There is substantial evidence suggesting that yoga lowers BP.[32],[35],[36] A significant reduction in systolic and diastolic BP and mean heart rate after the yoga intervention seen in our study is concurrent with studies done by Devasena and Narhare and Singh et al.[37],[38] These findings can be attributed to the fact that repeated yoga practice enhances baroreflex sensitivity while decreasing sympathetic tone, bringing BP to normal levels in individuals with hypertension.[39] The reduction in BP could also be a result of a shift in the autonomic nervous system toward parasympathetic dominance,[40],[41] reduced arterial stiffness, and enhanced endothelial function.[42]
One of the limitations of our study is that the control being a wait-listed group, it does not control completely for nonspecific effects of the experimental intervention such as expectation, belief, subject investment in time and effort, change in the subjects' daily routine, investigator interaction, social interaction and support, and the placebo effect. It was also not possible to blind the participants.
The present study is the first one to attempt an investigation into the molecular mechanism by which yoga helps hypertension. Further studies can be done with a larger sample size and more time points with specific biomarkers as an assessment tool that would further help in finding out basic mechanism (s).
Further, it would aid to incorporate mind-body techniques like yoga into the practice of scientific medicine if the studies not only establish that these approaches work, as well as how they function in terms of observable underlying mechanisms.
Conclusion The current study concludes that an IAYT-based yoga module was effective in improving autonomic modulation hence improving cardiovascular performance. Yoga also helped normalize lipid metabolism and ameliorating dyslipidemia, thereby mitigating CAD risk.
Hence, yoga could be adopted as a safe and inexpensive management strategy for hypertension.
Ethical statement
The study was approved by the Institutional Ethics committee of SDM College of Naturopathy and Yogic Sciences. (IEC Registration NO: EC-169).
Financial support and sponsorship
This work was supported by Rajiv Gandhi University of Health Sciences (Project Code: 17Y002). The sponsor had no influence on the planning or conduct of the study, on the acquisition, management, analysis, or interpretation of the data, on the writing, revision, or approval of the manuscript.
Conflicts of interest
There are no conflicts of interest.
References 
Correspondence Address:
Shivaprasad Shetty
Department of Yoga Therapeutics, SDMCNYS, Belthangady Taluk, Ujire - 574 240, Karnataka
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/ijoy.ijoy_107_22
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