The Effectiveness of Yoga in Modifying Risk

8/20/2019 The Effectiveness of Yoga in Modifying Risk

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EUROPEAN

SOCIET Y O F

CARDIOLOGY ® Original scientific paper

The effectiveness of yoga in modifying risk factors for cardiovascular disease andmetabolic syndrome: A systematic review

and meta-analysis of randomizedcontrolled trials

Paula Chu1,2, Rinske A Gotink 3,4, Gloria Y Yeh5, Sue J Goldie2,6

and MG Myriam Hunink 2,3,4,6

Abstract

Background: Yoga, a popular mind-body practice, may produce changes in cardiovascular disease (CVD) and metabolicsyndrome risk factors.Design: This was a systematic review and random-effects meta-analysis of randomized controlled trials (RCTs).Methods: Electronic searches of MEDLINE, EMBASE, CINAHL, PsycINFO, and The Cochrane Central Register of Controlled Trials were performed for systematic reviews and RCTs through December 2013. Studies were included if they were English, peer-reviewed, focused on asana-based yoga in adults, and reported relevant outcomes. Tworeviewers independently selected articles and assessed quality using Cochrane’s Risk of Bias tool.Results: Out of 1404 records, 37 RCTs were included in the systematic review and 32 in the meta-analysis. Comparedto non-exercise controls, yoga showed significant improvement for body mass index (0.77 kg/m2 (95% confidenceinterval 1.09 to 0.44)), systolic blood pressure (5.21 mmHg (8.01 to 2.42)), low-density lipoprotein cholesterol(12.14 mg/dl (21.80 to 2.48)), and high-density lipoprotein cholesterol (3.20 mg/dl (1.86 to 4.54)). Significantchanges were seen in body weight (2.32kg (4.33 to 0.37)), diastolic blood pressure (4.98 mmHg (7.17 to

2.80)), total cholesterol (18.48 mg/dl (29.16 to 7.80)), triglycerides (25.89 mg/dl (36.19 to 15.60), andheart rate (5.27 beats/min (9.55 to 1.00)), but not fasting blood glucose (5.91 mg/dl (16.32 to 4.50)) norglycosylated hemoglobin (0.06% Hb (0.24 to 0.11)). No significant difference was found between yoga and exercise.One study found an impact on smoking abstinence.Conclusions: There is promising evidence of yoga on improving cardio-metabolic health. Findings are limited by smalltrial sample sizes, heterogeneity, and moderate quality of RCTs.

Keywords

Yoga, cardiovascular disease, metabolic syndrome, systematic review, meta-analysis

Received 12 September 2014; accepted 14 November 2014

1Department of Health Policy, Harvard University, MA, USA2Center for Health Decision Science, Harvard School of Public Health,

MA, USA3Department of Epidemiology, Erasmus MC, the Netherlands4Department of Radiology, Erasmus MC, the Netherlands5Division of General Medicine and Primary Care, Harvard Medical

School, MA, USA

6Department of Health Policy and Management, Harvard School of Public

Health, MA, USA

Corresponding author:

MG Myriam Hunink, Departments of Radiology and Epidemiology, Room

Na 2818, Erasmus MC, PO Box 2040, 3000 CA Rotterdam, the

Netherlands.

Email: [email protected]

European Journal of Preventive

Cardiology

0(00) 1–17

! The European Society of

Cardiology 2014

Reprints and permissions:

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DOI: 10.1177/2047487314562741

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Introduction

Background

Cardiovascular disease (CVD) and metabolic syndrome

are major public health problems in the USA and

worldwide.1,2

Metabolic syndrome is defined ashaving at least three metabolic risk factors – increased

blood pressure, high blood sugar level, excess body fat,

and abnormal cholesterol levels – and greatly increases

the chance of future cardiovascular problems.3 Lifetime

risk of CVD is substantial as estimated through risk

functions like those from the Framingham Heart

Study,4 underlining the need for prevention and control

of risk factors.

CVD and metabolic syndrome share many of the

same modifiable risk factors. Several guidelines name

physical inactivity, the fourth leading risk factor of

global mortality,5 as an important modifiable risk

factor for CVD and metabolic syndrome.6–8 They

state that regular and adequate levels of physical activ-

ity in adults can reduce the risk of hypertension, cor-

onary heart disease, stroke, diabetes, and can help

maintain a healthy weight. Yoga, an ancient practice

from India that incorporates physical, mental, and spir-

itual elements, may be an effective form of physical

activity.

Yoga therapy

In recent years, clinical literature has reported cardio-

vascular health benefits from mind-body therapies.9–11

Yoga, one type of mind-body therapy, has been

increasing in popularity in the USA and in many

parts of the world. Yoga, meaning ‘‘union’’ in

Sanskrit, incorporates physical, mental, and spiritual

elements. In the West, Hatha yoga, one style of yoga,

has been most commonly practiced. Hatha yoga con-

sists of a series of physical exercises that focus on

stretching and stimulating the spine and muscles in

coordination with breath control, thought to stabilize

the hypothalamic-pituitary-adrenal axis and sym-

pathoadrenal activity.12–14 According to the 2007

National Health Interview Survey, about 20% of theUS population used some form of mind-body prac-

tice.15 Another study estimates that about 15 million

adults in America report having practiced yoga at

least once in their life,16 seeking wellness or treatment

for specific health conditions.

Rationale

A 2005 Cochrane study reviewed the evidence of yoga

for secondary prevention of coronary heart disease on

mortality, cardiovascular events, hospital admissions,

and quality of life and found no randomized controlled

trials (RCTs) meeting its inclusion criteria.17 Another

review done in 2005 examined CVD clinical endpoints

and insulin resistance with observational studies,

uncontrolled trials, and nonrandomized controlled

trials and found improvements in insulin resistance syn-

drome with yoga.13

Other reviews have shown yoga tobe beneficial in treatment of coronary heart disease,

post-myocardial infarction rehabilitation, and hyper-

tension.11,13,18–22 Since this time, several new RCTs

have been published. We sought to comprehensively

review recent RCT evidence of the effectiveness of

yoga on these risk factors and provide a pooled quan-

titative measure.

Objectives

Our objectives were (a) to identify and systematically

evaluate the evidence on the effectiveness of yoga for

modifying risk factors for CVD and metabolic syn-

drome in adult populations using published systematic

reviews, (b) to update the evidence by conducting a

systematic review of recent RCTs and (c) to estimate

a summary measure of effectiveness by conducting a

meta-analysis of the evidence of yoga’s effectiveness

versus no-exercise and exercise controls.

Methods

Data sources and search terms

The protocol for this review has been published on thePROSPERO website (http://www.crd.york.ac.uk/

PROSPERO) with the registration number

CRD42013006375. An amendment was added to the

protocol including an exercise control group and pub-

lished in an online revision note. Articles in this review

were identified by accessing the following biomedical

electronic databases with the assistance of a medical

librarian: MEDLINE, CINAHL, Cochrane Central

Register of Controlled Trials (CENTRAL), Cochrane

Database of Systematic Reviews, EMBASE, and

PsycINFO. Using existing published systematic reviews

(SRs) as a starting point for gathering evidence, SRsand/or meta-analyses were searched through December

2013. To collect any recent data that may have been

missed, we supplemented the search by searching for

RCTs published in the last three years through

December 2013. Citations were also retrieved by manu-

ally searching reference lists of relevant articles. The

databases were searched using the keywords ‘‘yoga’’

and ‘‘systematic review’’ for published SRs and

‘‘yoga’’ and ‘‘randomized controlled trials’’ for recent

RCTs (see online Supplementary Table S1 for search

strategies).

2 European Journal of Preventive Cardiology 0(00)

http://www.crd.york.ac.uk/PROSPEROhttp://www.crd.york.ac.uk/PROSPEROhttp://www.crd.york.ac.uk/PROSPEROhttp://www.crd.york.ac.uk/PROSPERO


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Study selection and inclusion process

Records were pooled from the various databases. Titles

and abstracts of SRs that appeared to meet the inclu-

sion criteria were retrieved for further evaluation.

Systematic reviews were defined as articles that

included an explicit and repeatable literature searchmethod and had explicit and repeatable inclusion and

exclusion criteria for studies. RCTs included in the SRs

were then retrieved. The process was repeated for the

supplementary search of RCTs.

For inclusion in our SR, the studies had to be pub-

lished in English in a peer-reviewed journal, be con-

ducted in adults (18þ years) who were either healthy,

at risk, or with a history of CVD or metabolic syndrome

and no other major comorbidities, test an asana- (or pos-

ture-) based intervention, and report relevant outcomes.

We focused only on SRs that included at least one ran-

domized controlled trial with yoga therapy as a trial arm.

No restrictions were placed on style of yoga practiced,

frequency, or duration. Articles were excluded if we were

unable toisolate the effect of yoga(i.e. yogawas part ofa

multimodal intervention whose non-yoga components

were given to the active intervention group but not to

the control group), outcomes reported only psychosocial

risk factors or psychological outcomes like stress and

anxiety, and the population treated focused on other

conditions or comorbidities (e.g. women with breast

cancer, populations with renal disease). Two investiga-

tors (PC and RG) independently selected studies for

inclusion; disagreements were resolved by discussion.

Outcomes

The outcomes of interest were changes in the levels of

modifiable risk factors for CVD and metabolic syn-

drome. Particularly, we were interested in measures of

body composition, blood pressure, lipid panel, glycemic

control, heart rate, and smoking status. Primary out-

comes include body mass index (BMI), systolic blood

pressure (SBP), low-density lipoprotein cholesterol

(LDL-C), and high-density lipoprotein cholesterol

(HDL-C). Other outcomes – body weight, diastolic

blood pressure (DBP), total cholesterol (TC), triglycer-ides (TG), fasting blood glucose (FBG), glycosylated

hemoglobin (HbA1c), heart rate, and smoking status

– were considered secondary outcomes. Outcomes

were kept in their natural units.

Data extraction and quality assessment

From each eligible study we extracted the characteris-

tics of the participants, intervention description (type,

length of session, frequency), control group description,

duration of follow-up, number of patients randomized

at baseline and number at follow-up, and effect meas-

ures (pre- and post-mean and standard deviations in

intervention and control arms, mean change scores

and standard deviations if reported). Data from the

longest follow-up was extracted. Data extraction was

performed by one investigator (PC) and checked for

accuracy and completeness by a second reviewer(RG). Any discrepancies were resolved by discussion.

RCTs were appraised using the Cochrane

Collaboration’s Risk of Bias (ROB) tool, a commonly

used tool to assess risk of bias.23 Trial quality was eval-

uated by using categories of high, low, or unclear risk in

regards to randomization method, allocation conceal-

ment, blinding of study personnel and outcomes assess-

ment, attrition, and reporting methods. Two reviewers

(PC and RG) independently evaluated RCT quality

and resolved any discrepancies by discussion.

Statistical analysisChange scores, mean differences (MDs) between treat-

ment arms, and sample sizes reported were on an inten-

tion-to-treat basis. MDs were calculated by subtracting

the change score in the control group from the change

score in the yoga group. Where MDs and standard

deviations were not reported, standard deviations

were calculated using a conservative correlation coeffi-

cient of 0.5 for within-patient correlation from baseline

to follow-up. MDs between groups and 95% confi-

dence intervals (CIs) were calculated for each outcome.

The magnitude of heterogeneity was evaluated using

the I 2

statistic testing the null hypothesis that all studiesare evaluating the same effect.24 I 2 values of 25%, 50%,

and 75% correspond to low, moderate, and high het-

erogeneity, respectively. Because meta-analysis pools

studies that are clinically and methodologically diverse,

data on MDs from trials were statistically pooled using

a random effects model.25 We also categorized patients

into four subgroups based on patient conditions –

healthy, with CVD risk factors, with diabetes or meta-

bolic syndrome, and diagnosed with coronary artery

disease (CAD) – to depict heterogeneity in the popula-

tions included and their response to treatment. Healthy

patients are those free of clinical manifestations of anymedical or psychiatric illness including clinically signifi-

cant CVD and diabetes mellitus. Those with CVD risk

factors included patients with hypertension, high chol-

esterol levels, obesity, and current smokers. Diabetes

and metabolic syndrome were diagnosed through med-

ical examination or history, and CAD was confirmed

through angiography.

Controls were separated into aerobic exercise (phys-

ical training, aerobic exercise, cycling, running, brisk

walking) and non-aerobic exercise groups. Yoga was

compared to these two control groups separately to

Chu et al. 3


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obtain an estimate of its effectiveness versus active con-

trols and versus non-active controls (details published

in protocol amendment). Reference Manager

(RevMan) Version 5.2 software from the Cochrane

Collaboration was used for data analysis.26

Publication bias

Publication bias was assessed for each of the primary

outcomes by visual inspection of funnel plots generated

using RevMan software. The MDs were plotted on the

x-axis and the standard errors, a measure of study size,

on the y-axis. In the absence of bias, the scatterplot

should be approximately symmetrical; the more asym-

metry, the more bias is present.

Results

Literature searchWe identified 643 studies from the SR search and 761

studies from the RCT search for a total of 1404 records

(Figure 1). After removal of duplicates, a total of 880

titles and abstracts were screened. A total of 37 RCTs

(24 RCTs from 18 SRs and 13 additional RCTs) met

our criteria for inclusion in the review. Although 37

studies met criteria, five studies did not report exact

numbers for our primary or secondary outcomes and

could not be included in the meta-analysis,27–31

leaving32 studies for statistical analysis.

Study quality

Study quality and description of methodology varied

amongst the included studies (see Table 1). Thirteen

studies32–43 provided details on the specific randomiza-

tion method that was used in the RCT and

four31,35,37,38 described treatment assignment. Due to

the nature of the intervention, all studies had high

risk of bias for blinding of participants; however,

three studies reported blinding of the personnel, indi-

cating that technicians were blinded to treatment

assignment of individuals.34,44,45 Almost all studies

except one34 had unclear risk for blinding of outcome

643 potentially relevantrecords identified from

database and hand search

246 duplicatesremoved

PUBMED(194)

EMBASE(283)

MANUALSEARCH

(1)

CINAHL(105)

PSYCINFO(60)

23 SRs includedcontaining

99 potential RCTs

397 titles and abstractsreviewed

Articles excluded (n=343):

Not English language (n=8)Not systematic review (n=78)

Effectiveness of yoga not mainresearch question (n=21)

Not in adult population (n=14)Reported outcomes not related to

CVD, risk facto rs for CVD, orcardiometabolic disorders (n=178)

Other populations (n=11)Reported outcomes focus

exclusively on psychologicaloutcomes (n=32)

Full-text no t available (n =1)54 full text po tential SRs

assessed for eligibility

Articles excluded (n=31):Not systematic review (n=15)


Reported outcomes not related toCVD, risk facto rs for CVD, or

cardiometabolic disorders (n=2)Reported outcomes focus

exclusively on psychologicaloutcomes (n=3)

No eligible RCTs found (n=6)Unable to isolate e ffect of yoga

(n=1)Other populations (n=2)

Not asana-based (n=1)

24 RCTs from SRsincluded

Articles excluded (n=22):Not RCT (n=3)

Not in adult population (n=1)Other populations (n=2)

Not asana-based (n=9)Does not c ontain the outcomes of

interest (n=3)Full-text n ot available (n=1)

53 duplicate RCTsremoved

46 full text potential RCTsfrom SRs reviewed

PUBMED(227)

761 potentially relevantrecords identified from

database and manualsearch

278 duplicatesremoved

EMBASE(343)

MANUAL

SEARCH(2)

CINAHL(95)

COCHRANECENTRAL

(94)

13 RCTs included insystematic review

483 titles and abstractsreviewed Articles excluded (n=447):

Not RCT (n=59)Effectiveness of yoga not mainresearch question (n=25)Not in adult population (n=24)Reported outcomes not related toCVD, risk factors for CVD, orcardiometabolic disorders (n=273)Reported outcomes focusexclusively on psychologicaloutcomes (n=31)Other populations (n=19)Not asana-based (n=4)Full text not available (n=12)

36 full text articlesassessed for eligibility

Articles excluded (n=23):Already included in systematic

review search (n=3)Not RCT (n=5)


Reported outcomes not related toCVD, risk factors for CVD, or

cardiometabolic disorders (n=3)Unable to isolate effect of yoga

(n=1)Other populations (n=1)

Not asana-based (n=8)

SYSTEMATIC R EVIEW SEAR CH RANDOMIZED CONTROLLED TRIAL SEARCH

Figure 1. Flowchart depicting the search and screening process of systematic reviews and randomized controlled trials (RCTs).

CVD: cardiovascular disease.



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T a b l e

1 . C o n t i n u e d .

S

t u d y

F r o m S R

T o t a l n

o .

r a n d o m

i z e d

( y o g a / c

o n t r o l )

T o t a l n o . a t f o l l o w - u p

( y o g a / c

o n t r o l )

T r e a t m e n t g r o u p

M e a n a g e S

D

A g e r a n g e

% f e m a l e

I n t e r v e n t i o n T i m e

p e r s e s s i o n

C o n

t r o l

F r e q u e n c y D u r a t i o n O

u t c o m e m e a s u r e s

S t u d y q u a l i t y a

N o . o f d o m a i n s

a t l o w / u n c l e a r /

h i g h r i s k

V

o g l e r e t a l .

( 2 0 1 1 ) 2 9 , b

4 0 ( 2 0 / 2 0 )

3 8 ( 1 9 / 1 9 )

P h y s i c a l l y i n a c t i v e

o l d e r a d u l t s

Y o g a 7 6 , c o n t r o l 7 2

R a n g e : 5 6

– 9 4

N R

I y e n g a r y o g a 9 0 m i n

H o m e p r a c t i c e

1 5 – 2 0 m i n

U s u a l d a i l y r o u t i n e

2 x / w e e k

3 x / w e e k ( h o m e

p r a c t i c e )

8 w e e k s

S B

P , D B P

2 / 3 / 1

K

a n o j i a e t a l .

( 2 0 1 3 ) 6 4

5 0 ( 2 5 / 2 5 )

5 0 ( 2 5 / 2 5 )

Y o u n g h e a l t h y

f e m a l e s

Y o g a 1 8 . 6

1 . 1 ,

c o n t r o l

1 8 . 1 0 . 8

R a n g e : 1 8

– 2 0

1 0 0

Y o g a 4 0 m i n

N o i n t e r v e n t i o n

6 x / w e e k

B W , S B P , D B P , H R

2 / 3 / 1

K

i m e t a l . ( 2 0 1 2 ) 6 5

4 7 ( 2 7 / 2 0 )

3 4 ( 1 6 / 1 8 )

N o r m a l p r e m e n o -

p a u s a l w o m e n

Y o g a 4 5 . 7

5 . 2 ,

c o n t r o l

4 3 . 2 4 . 5

R a n g e : 3 5

– 5 0

1 0 0

A s h t a n g a y o g a

6 0 m i n

N o r m a l d a i l y l i f e s t y l e s

2 x / w e e k

3 2 w e e k s

S B

P , D B P , H R

1 / 4 / 1

W

o l e v e r e t a l .

( 2 0 1 2 ) 6 6

2 3 9 ( 9 0 / 9 6 / 5 3 )

2 0 5

( 7 6 / 8 2 / 4 7 )

E m p l o y e e s o f a

n a t i o n a l i n s u r -

a n c e c a r r i e r

Y o g a 4 1 . 6 1 0 . 1 , c o n -

t r o l 4 4 . 3

9 . 4

( 1 ) , 4 2 . 7

9 . 7 ( 2 )

7 7

V i n i y o g a s t r e s s

r e d u c t i o n p r o -

g r a m 6 0 m i n

1 . M

i n d f u l n e s s a t W o r k p r o -

g

r a m

2 . L i s t o f r e s o u r c e s

1 x / w e e k

1 2 w e e k s

S B

P , D B P

2 / 3 / 1

T

r a c y e t a l . ( 2 0 1 3 ) 3 0 , b

3 2 ( 2 1 / 1 1 )

2 1 ( 1 0 / 1 1 )

Y o u n g h e a l t h y a d u l t s

Y o g a 2 9 6 ,

c o n t r o l

2 6

7

R a n g e : 2 1

– 3 9

5 2

B i k r a m y o g a 9 0 m i n

N o r m a l l i f e s t y l e

3 x / w e e k

8 w e e k s

S B

P , H R

0 / 3 / 3

A

d u l t s w i t h C V D r i s k f a c t o r s

V

a n M o n t f r a n s e t a l .

( 1 9 9 0 ) 6 7

I n n e s e t a l . ( 2 0 0 5 ) , 1 3

H a g i n s e t a l .

( 2 0 1 3 ) 1 9

4 2 ( 2 3 / 1 9 )

3 5 ( 1 8 / 1 7 )

A d u l t s w i t h m i l d u n -

c o m p l i c a t e d

h y p e r t e n s i o n

Y o g a 4 0 , c o n t r o l 4 3

R a n g e : 2 4

– 6 0

4 9

H a t h a y o g a þ

p r o -

g r e s s i v e m u s c l e

r e l a x a t i o n þ

s t r e s s m a n a g e -

m e n t 6 0 m i n

P a s s i v e r e l a x a t i o n

1 x / w e e k ; 2 x / w e e k

( h o m e p r a c t i c e )

5 2 w e e k s

B W , S B P , D B P , T C

2 / 3 / 1

M

a h a j a n e t a l .

( 1 9 9 9 ) 5 4

I n n e s e t a l . ( 2 0 0 5 ) , 1 3

J a y a s i n g h e

( 2 0 0 4 ) , 1

1

Y a n g

( 2 0 0 7 ) , 6

2

P a t e l

e t a l . ( 2 0 1 2 ) 6 0

9 3 ( 5 2 / 4 1 )

9 3 ( 5 2 / 4 1 )

A n g i n a p a t i e n t s a n d

a s y m p t o m a t i c

p a r t i c i p a n t s w i t h

C A D r i s k f a c t o r s

R a n g e : 5 6 – 5 9

0

4 d y o g a c a m p þ

d i e t ;

y o g a p r a c -

t i c e þ

l i f e s t y l e

a d v i c e

6 0 m i n

C o n

v e n t i o n a l t h e r a p y ( d i e t

c

o n t r o l , m o d e r a t e a e r -

o

b i c e x e r c i s e a s

p

r e s c r i b e d ) þ

l i f e s t y l e

a

d v i c e

4 d a y s þ

7 x / w e e k

1 4 w e e k s

B W , T C , L D L - C ,

H D L - C , T G

1 / 4 / 1

M

u r u g e s a n e t a l .

( 2 0 0 0 ) 5 3

I n n e s e t a l . ( 2 0 0 5 ) , 1 3

J a y a s i n g h e

( 2 0 0 4 ) , 1

1

N i c o l s o n e t a l .

( 2 0 0 4 ) , 6

8

I n n e s

e t a l . ( 2 0 0 7 ) , 1

4

P a t e l e t a l .

( 2 0 1 2 ) , 6

0

H a g i n s

e t a l . ( 2 0 1 3 ) , 1

9

W a n g e t a l .

( 2 0 1 3 ) 6 9

3 3 ( 1 1 / 1 1 / 1 1 )

3 3 ( 1 1 / 1 1 / 1 1 )

H y p e r t e n s i v e

p a t i e n t s

R a n g e : 3 5 – 6 5

N R

Y o g a 6 0 m i n

1 . D

a i l y m e d i c a l t r e a t m e n t

w

i t h a n t i h y p e r t e n s i v e s

2 . N

o i n t e r v e n t i o n

7 x / w e e k

1 1 w e e k s

B W , S B P , D B P

2 / 3 / 1

M

c C a f f r e y e t a l .

( 2 0 0 5 ) 3 9


( 2 0 1 3 ) , 1

9

R i o u x

e t a l . ( 2 0 1 3 ) , 7

0

6 1 ( 3 2 / 2 9 )

5 4 ( 2 7 / 2 7 )

A d u l t s w i t h d i a g -

n o s e d h y p e r t e n -

s i o n n o t

Y o g a 5 6 . 7 , c o

n t r o l

5 6 . 2

6 5

Y o g a p r a c t i c e w i t h

i n s t r u c t i o n a l

G e n e r a l e d u c a t i o n a b o u t

h

y p e r t e n s i o n

3 x / w e e k

8 w e e k s

B M I , S B P , D B P , H R

2 / 2 / 2 ( c

o n t i n u e d )


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T

a b l e

1 . C o n t i n u e d .

S t u d y

F r o m S R

T o t a l n o

.

r a n d o m i z e d

( y o g a / c o

n t r o l )

T o t a l n o

. a t f o l l o w - u p

( y o g a / c o

n t r o l )


M e a n a g e S D

A g e r a n g e

% f e m a l e


p e r s e s s i o n

C o n t r o l

F r e q u e n c y D u r a t i o n

O u

t c o m e m e a s u r e s




h i g h r i s k

W a n g e t a l .

( 2 0 1 3 ) 6 9

c u r r e n t l y t a k i n g

m e d i c a t i o n

b o o k l e t a n d t a p e

6 3 m i n

C

o h e n e t a l . ( 2 0 1 1 ) 7 1

W a n g e t a l . ( 2 0 1 3 ) , 6 9


( 2 0 1 3 ) 1 9

7 8 ( 4 6 / 3 2 )

5 7 ( 2 6 / 3 1 )

A d u l t s w i t h

u n t r e a t e d p r e -

h y p e r t e n s i o n o r

S t a g e 1 h y p e r -

t e n s i o n n o t

t a k i n g a n t i - h y p e r -

t e n s i v e

m e d i c a t i o n

Y o g a 4 8 . 2 1 . 6 ,

c o n t r o l

4 8 . 3

2 . 4

R a n g e : 2 2 – 6 9

5 0

I y e n g a r y o g a 7 0 m i n

( c l a s s e s a l l w e e k s ,

2 5 m i n h o m e

p r a c t i c e w e e k s

6 – 1 2 )

E n h a n c e d u s u a l c a r e w i t h

d i e t a r y e d u c a t i o n

2 x / w e e k f i r s t 6

w e e k s ; 1 x / w e e k

n e x t 6 w e e k s

1 2 w e e k s

B W

, S B P , D B P , H R

1 / 3 / 2

S u b r a m a n i a n e t a l .

( 2 0 1 1 ) 4 8

H a g i n s e t a l . ( 2 0 1 3 ) 1 9

1 0 0 ( 2 5 / 2 5 / 2 5 / 2 5 )

9 4 ( 2 5 / 2 5 / 2 3 / 2 1 )

Y o u n g a d u l t s w i t h

p r e - h y p e r t e n s i o n

a n d h y p e r t e n s i o n

n o t t a k i n g a n t i -

h y p e r t e n s i v e

m e d i c a t i o n

Y o g a 2 3 , c o n t r o l 2 3 . 3

( 1 ) , 2 3 . 7 ( 2 ) , 2 3 . 7

( 3 )

3 3

Y o g a 3 0 – 4 5 m i n

1 . N o

i n t e r v e n t i o n ;

2 . p h y s i c a l e x e r c i s e ( b r i s k

w

a l k i n g ) 5 0 – 6 0 m i n ; 3 . S a l t

i n

t a k e r e d u c t i o n t o a t

l e a s t h a l f p r e v i o u s i n t a k e

5 x / w e e k

8 w e e k s

S B P , D B P

2 / 3 / 1

B o c k e t a l . ( 2 0 1 2 ) 3 2

C a r i m - T o d d e t a l .

( 2 0 1 3 ) 7 2

5 5 ( 3 2 / 2 3 )

5 5 ( 3 2 / 2 3 )

M i d d l e a g e f e m a l e

s m o k e r s t h a t

i n t e n d e d t o q u i t

s m o k i n g

4 5 . 6

8 . 3

1 0 0

V i n y a s a y o g a þ

C B T

W e l l n e s s s e s s i o n s f o r h e a l t h

e d u c a t i o n þ

C B T

2 x / w e e k

8 w e e k s

7 - d

a y p o i n t - p r e v a -

l e n c e s m o k i n g

a b s t i n e n c e

3 / 2 / 1

L e e e t a l . ( 2 0 1 2 ) 7 3

1 6 ( 8 / 8 )

1 6 ( 8 / 8 )

O b e s e p o s t m e n o -

p a u s a l w o m e n

Y o g a 5 4 . 5

2 . 8 ,

c o n t r o l

5 4 . 3

2 . 9

1 0 0 %

Y o g a 6 0 m i n

N o e

x e r c i s e

3 x / w e e k

1 6 w e e k s

B W

, B M I , T C , L D L -

C , H D L - C , T G ,

F B G

2 / 3 / 1

A d u l t s w i t h d i a b e t e s o r m e t a b o l i c s y n d r o m e

M

o n r o e t a l . ( 1 9 9 2 ) 5 2

I n n e s e t a l . ( 2 0 0 5 ) , 1 3

A l j a s i r e t a l .

( 2 0 1 0 ) , 7

4

I n n e s

e t a l . ( 2 0 0 7 ) , 1 4

P i l k i n g t o n e t a l .

( 2 0 0 7 ) 7 5

2 1 ( 1 1 / 1 0 )

2 1 ( 1 1 / 1 0 )

P a t i e n t s w i t h n o n -

i n s u l i n - d e p e n d e n t

D M c o n t r o l l e d

w i t h m e d i c a t i o n

o r d i e t

Y o g a 5 3 , c o n t r o l 5 7

N R

Y o g a þ

n o r m a l m e d i -

c a t i o n a n d d i e t

9 0 m i n

U s u a l c a r e ( c o n t i n u a t i o n o f

m

e d i c a t i o n , d i e t )

2 – 4 x / w e e k

1 2 w e e k s

F B G , H b A 1 c

1 / 3 / 2

K e r r e t a l . ( 2 0 0 2 ) 3 1 , b

I n n e s e t a l . ( 2 0 0 7 ) , 1 4

P i l k i n g t o n e t a l .

( 2 0 0 7 ) 7 5

3 7 ( 1 7 / 2 0 )

3 3 ( 1 7 / 1 6 )

P a t i e n t s w i t h p o o r l y

c o n t r o l l e d t y p e 1

a n d 2 D M

Y o g a 6 0 . 3 7 . 8 ,

c o n t r o l

6 1 . 4

1 0 . 7

N R

H a t h a y o g a þ

e d u c a -

t i o n þ

c o n t i n u e d

i n s u l i n

9 0 m i n

E d u c a t i o n þ

s i m p l e e x e r -

c i s e s þ

c o n t i n u e d i n s u l i n

2 x / w e e k

1 6 w e e k s

B W

, B M I , T C , L D L -

C , H D L - C , T G ,

H b A 1 c

1 / 2 / 3

C

o h e n e t a l . ( 2 0 0 8 ) 3 3

A n d e r s o n e t a l .

( 2 0 1 1 ) , 5

7

S h a r m a

e t a l . ( 2 0 1 2 ) , 7 6


( 2 0 1 3 ) 1 9

2 6 ( 1 4 / 1 2 )

2 4 ( 1 2 / 1 2 )

U n d e r a c t i v e , o v e r -

w e i g h t a d u l t m e n

a n d w o m e n w i t h

m e t a b o l i c s y n -

d r o m e n o t t a k i n g

m e d i c a t i o n

Y o g a 5 2 9 , c o n t r o l

5 2

8

R a n g e : 3 0 – 6 5

8 5

Y o g a 9 0 m i n þ

3 h r i n t r o

W a i t i n g l i s t

2 x / w e e k f o r 5

w e e k s , t h e n

1 x / w e e k f o r 5

w e e k s ; 3 x / w e e k

( h o m e p r a c t i c e )

1 0 w e e k s

B W

, B M I , S B P , D B P ,

T C , L D L - C ,

H D L - C , T G , F B G

3 / 2 / 1 ( c

o n t i n u e d )


8/17


9/17

T a

b l e

1 . C o n t i n u e d .

S t u d y

F r o m S R

T o t a l n o .

r a n d o m i z e d

( y o g a / c o n t r o l )

T o t a l n o . a t f o l l o w - u p

( y o g a / c o n t r o l )


M e a n a g e

S D

A g e r a n g e

% f e m a l e


p e r s e s s i o n

C o n t r o

l

F r e q u e n c y D u r a t i o n

O u t c o m e m e a s u r e s




h i g h r i s k

J a t u

p o r n e t a l .

( 2 0 0 3 ) 5 5

I n n e s e t a l . ( 2 0 0 5 ) 1 3

4 4 ( 2 2 / 2 2

)

4 4 ( 2 2

/ 2 2 )

A d u l t s w i t h C A D

w i t h o u t p r i o r

t h e r a p e u t i c

i n t e r v e n t i o n

Y o g a 6 1 . 5 4 . 7 ,

c o n t r o l

5 6 . 8

7 . 6

2 0

I n t e n s i v e l i f e s t y l e

m o d i f i c a t i o n

w i t h o u t l i p i d -

l o w e r i n g d r u g s

( y o g a , s u p p o r t ,

d i e t a r y a d v i c e ,

r e l a x a t i o n )

6 0 m i n

C o n v e n t i o n a l t r e a t m e n t w i t h

l i p i d

- l o w e r i n g d r u g s

3 x / w e e k

1 6 w e e k s

B M I ,

T C , L D L - C ,

H

D L - C , T G

2 / 3 / 1

A d e

s e t a l . ( 2 0 0 5 ) 4 3

P a t e l e t a l . ( 2 0 1 2 ) 6 0

5 1 ( 2 5 / 2 6

)

4 2 ( 2 1

/ 2 1 )

C o m m u n i t y - d w e l l i n g

w o m e n w i t h

e s t a b l i s h e d C A D

f o r a t l e a s t 6

m o n t h s

Y o g a : 7 1 . 5 4 . 8

,

c o n t r o l

7 2 . 9

6 . 1

R a n g e : > 6 5

1 0 0

L i g h t y o g a þ

c o n t i n -

u e d m e d i c a t i o n

a s i n c o n t r o l

3 0 – 4 0 m i n

R e s i s t a n c e e x e r c i s e t r a i -

n i n g þ

c o n t i n u e d m e d i c a -

t i o n

( a s p i r i n , b - a d r e n e r g i c

b l o c k e r s , n i t r a t e s , c a l -

c i u m

- b l o c k e r s )

3 x / w e e k

2 4 w e e k s

B W ,

B M I

3 / 2 / 1

P a l

e t a l . ( 2 0 1 1 ) 3 5

1 6 0 ( 8 5 / 8

5 )

1 5 4 ( 8

0 / 7 4 )

P a t i e n t s d i a g n o s e d

w i t h C A D

Y o g a 5 8 . 9 9 . 4 ,

c o n t r o l

5 8 . 6

1 0 . 5

1 6

Y o g a þ

m e d i c a t i o n a s

i n c o n t r o l

3 5 – 4 0 m i n

M e d i c a t i o n o n l y ( m e t o p r o l o l /

a t e n o l o l , a s p i r i n , c l o p i d o -

p r i l , a t o r v a s t a t i n / r o s u v a s -

t a t i n , r a m i p r i l / l o s a r t a n /

t e l m

i s a r t a n )

5 x / w e e k

2 4 w e e k s

B M I ,

S B P , D B P , T C ,

L D L - C , H D L - C ,

T

G , H R

4 / 1 / 1

P a l

e t a l . ( 2 0 1 3 ) 3 6

2 5 8 ( 1 2 9 / 1 2 9 )

2 0 8 ( 1

0 5 / 1 0 3 )

P a t i e n t s d i a g n o s e d

w i t h C A D

Y o g a 5 9 . 1 9 . 9 ,

c o n t r o l

5 6 . 4

1 0 . 9

2 0

Y o g a þ

m e d i c a t i o n a s

i n c o n t r o l

3 5 – 4 0 m i n

M e d i c a t i o n o n l y ( m e t o p r o l o l /

a t e n o l o l , a s p i r i n , c l o p i d o -

p r i l , a t o r v a s t a t i n / r o s u v a s -

t a t i n , r a m i p r i l / l o s a r t a n /

t e l m

i s a r t a n )

5 x / w e e k

7 2 w e e k s

B M I ,

S B P , D B P , H R

2 / 3 / 1

A H

A : A m e r i c a n H e a r t A s s o c i a t i o n ; B M I : b o d y m

a s s i n d e x ; B W : b o d y w e i g h t ; C A D : c o r o n a r y

a r t e r y d i s e a s e ; C B T : c o g n i t i v e b e h a v i o r a l t h e r a p y ; D B P : d i a s t o l i c b l o o d p r e s s u r e ; D M : d i a b e t e s m e l l i t u s ; F B G : f a s t i n g b l o o d

g l u c o s e ; H b A 1 c : g l y c o s y l a t e d h e m o g l o b i n ; H D L - C

: h i g h - d e n s i t y l i p o p r o t e i n c h o l e s t e r o l ; L D L - C : l o w - d e n s i t y l i p o p r o t e i n c h o l e s t e r o l ; N R : n o t

r e p o r t e d ; S B P : s y s t o l i c b l o o d p r e s s u r e ; S D : s t a n d a r d d e v i a t i o n ; S R : s y s t e m a t i c

r e v i e w ; T C : t o t a l c h o l e s t e r o l ; T G : t r i g l y c e r i d e s ; H R : h e a r t r a t e .

a B a s e d o n t h e C o c h r a n e C o l l a b o r a t i o n ’ s r i s k o f b i a s t o o l , n u m b e r s c o r r e s p o n d t o n u m b e r r a t e d l o w r i s k , u n c l e a r r i s k , a n d h i g h r i s k o n s i x

d o m a i n s .

b F i n d i n g s o n l y d e s c r i b e d i n t e x t , n u m b e r s n o t r e p o r t e d .

U n l e s s o t h e r w i s e n o t e d , t h e y o g a g r o u p a l s o r e c

e i v e d u s u a l c a r e i n a d d i t i o n t o t h e l i s t e d i n t e r v e n t i o n s .


10/17

assessment. However, there was generally low risk of

bias for incomplete reporting of outcomes and

selective reporting of outcomes. A summary of

study quality can be seen in online Supplementary

Figure S1.

Study characteristics

Characteristics of the included studies are listed in

Table 1. The included studies comprised a total of

2768 participants, with about an equal mix of men

(47%) and women (53%). RCTs included adult partici-

pants of all ages with an average age of 50 years. Of

these participants, 1287 (47%) were assigned to receive

the yoga intervention and 1461 (53%) assigned to the

control arm. Altogether 1094 (85%) of yoga partici-

pants completed the study while 1301 (89%) of control

participants made it to follow-up. Duration of studies

varied, with follow-up times ranging from 3 weeks to 52

weeks, with a median of 12 weeks. Dividing into sub-

groups, 38% (14/37) of studies were conducted

in healthy populations, 22% (8/32) of studies in popu-

lations with CVD risk factors, 27% (10/32) in popula-

tions with diabetes or metabolic syndrome, and 13%

(5/32) in populations with CAD.

Control arms included usual care or conventional

medical therapy (23%), a form of relaxation (6%), edu-

cation (11%), diet alone (4%), waiting list or no inter-

vention (32%), cognitive-based therapy (2%), and

exercise (21%). Five two-arm RCTs,41–43,46,47 three

three-arm RCTs,27,40,45 and one four-arm RCT48 used

exercise as one of the comparator strategies. Exercisecontrols consisted of physical training, cycling, run-

ning, brisk walking, or resistance training.43 One exer-

cise trial27 was excluded from the meta-analysis due to

incomplete reporting of effect measures.

Risk factor outcomes

Yoga versus non-exercise controls. Yoga showed significant

improvement of risk factors versus non-exercise con-

trols for each of the primary outcomes: BMI

(0.77 kg/m2 (1.09 to 0.44)), SBP (5.21 mmHg

(

8.01 to

2.42)), LDL–C (

12.14 mg/dl (

21.80 to2.48)), and HDL-C (3.20 mg/dl (1.86 to 4.54))

(Figure 2). For the secondary outcomes, significant

improvement was seen in all risk factors except FBG

(5.91 mg/dl (16.32 to 4.50)) and HbA1c (0.06%

Hb (0.43 to 0.31)) (online Supplementary Figure

S2). Improvements reported in secondary outcomes

include reductions of body weight (2.35 kg (4.33 to

0.37)), DBP (4.98 mmHg (7.17 to 2.80)), TC

(18.48 (29.16 to 7.80), TG (25.89 mg/dl

(36.19 to 15.60)), and heart rate (5.27 beats/min

(9.55 to 1.00)) (online Supplementary Figure S2).

Only one trial was found which evaluated the impact

of yoga on smoking status.32 When twice-weekly

Vinyasa-style yoga was given in addition to cognitive

behavioral therapy (CBT) for smoking cessation, smo-

kers in the intervention group had higher odds of seven-

day and 24-hour abstinence compared to a control

group receiving CBT and education at the end of theeight-week study period (seven-day quit odds ratio

(OR) 4.56 (95% CI 1.12 to 18.57), 24-hour quit OR

4.19 (1.16 to 15.11). These results did not last, however,

when abstinence was measured at six-month follow-up

(seven-day quit OR 1.54 (0.34 to 6.92), 24-hour quit

OR 1.87 (0.43 to 8.16)).

When yoga is used in addition to medication, sig-

nificant improvement was found in body weight,49

BMI,35,36 blood pressure,20,50 lipid levels,35,38,49,51

FBG,38,52 HbA1c,38,52 and heart rate36 in patients

with type 2 diabetes or CAD. As a substitute for med-

ical therapy, results are less definitive. Two RCTs

found yoga more effective than drug therapy in con-

trolling blood pressure53 and body weight.53,54 In a

three-arm trial in which yoga was directly compared

to a group that received antihypertensive treatment

and a group receiving no treatment in patients at

high risk for CVD, yoga reduced SBP almost three

times more than the antihypertensive therapy (MD

29.17 mmHg (37.75, 20.59) and 9.60 mmHg

(18.78, 0.42), respectively).53 When yoga is

included in addition to continued medication in

CAD patients, an additional benefit, although smaller,

is still observed.35,36 Among CAD patients, yoga is

less effective as a substitute for medication such asstatins and lipid-lowering drugs in lowering LDL-

C;55 however, as an adjunct treatment to medication,

yoga provides an additional statistically significant

benefit.35,49

Yoga versus exercise. Five out of nine trials comparing

yoga to exercise were conducted in healthy popula-

tions27,41,42,46,47,56 and the remaining were conducted

in young patient populations with hypertension,40,48

an elderly female population with CAD,43 and a popu-

lation with type 2 diabetes mellitus.45

Among the outcomes that were reported by morethan one study, there was no significant difference in

the effectiveness of yoga versus aerobic exercise in mod-

ifying body weight (0.61kg (2.70, 1.49)),41,43,47

SBP (0.64 mmHg (6.71, 5.43)),40,42,46–48 DBP

(0.14 mmHg (5.73, 5.44)),40,42,47,48 and heart rate

(1.42 beats/min (6.11, 3.27))41,42,46,47,56 (Figure 3).

In addition, there was also no difference comparing

the two strategies for BMI,43 LDL-C,45 HDL-C,45

TC,45 TG,45 or FBG.45

When all studies were pooled together, all trends

remained irrespective of controls. MDs in risk factor



11/17

Figure 2. Forest plots of body mass index, systolic blood pressure, low-density lipoprotein, and high-density lipoprotein cholesterol

results. Negative mean differences between groups favor the yoga intervention, positive mean differences favor control.

CAD: coronary artery disease; CI: confidence interval; CVD: cardiovascular disease; SD: standard deviation.

Chu et al. 11


12/17

Figure 2. Continued.



13/17

reductions changed only slightly (online Supplementary

Table S2).

Publication bias

Funnel plots assessing publication bias of the primary

outcomes are shown in online Supplementary Figure

S3. As the funnel plots are mostly symmetrical, we do

not find evidence of strong publication bias.

Discussion

The review shows that the practice of yoga may be bene-

ficial to managing and improving risk factors associated

with CVD and metabolic syndrome. This finding, how-

ever, should be cautiously interpreted as the RCTs

included were of limited sample size, heterogeneous, andhad unclear or high risk of bias on several domains. When

trials were pooled, all but two of the outcomes examined

in this review showed improvement after a yoga interven-

tion when compared to non-exercise controls.

Compared to traditional aerobic exercise controls,

there was no significant difference in how exercise or

yoga changed risk factors, suggesting similar effective-

ness of the two forms of physical activity and possibly

similar underlying mechanisms. The mechanism behind

the therapeutic effect of yoga for CVD is still unclear;

studies have suggested that yoga may modulate

Figure 3. Forest plots of yoga versus physical exercise results for body weight, systolic blood pressure, diastolic blood pressure, and

heart rate.

CI: confidence interval; SD: standard deviation.

Chu et al. 13


14/17

autonomic function and beneficially alter markers of

sympathetic and parasympathetic activity.12–14

Through practicing yoga, the effects of stress can be

reduced, leading to positive impacts on neuroendocrine

status, metabolic and cardio-vagal function, and related

inflammatory responses.12–14 The similarity in effective-

ness on risk factors between the two forms of exercisesuggest that there could be comparable working mech-

anisms, with some possible physiological aerobic benefits

occurring with yoga practice, and some stress-reducing,

relaxation effect occurring with aerobic exercise.

This review helps strengthen the evidence base for

yoga as a potentially effective therapy for cardiovascu-

lar and metabolic health. Our results support earlier

reviews on the positive benefits of yoga on primary

and secondary prevention of CVD and metabolic syn-

drome.11,13,18–20,22,50,57 Two systematic reviews that

were recently published find that there is some evidence

for yoga having favorable effects on CVD risk fac-

tors.58,59 One review, conducted by the Cochrane

Collaboration, included 11 trials with its more restrict-

ive inclusion criteria and found significant improve-

ment in DBP, TG, and HDL.59 The second review,

with broad inclusion criteria and a wider list of out-

comes, included 44 trials and found that yoga improves

SBP, DBP, heart rate, respiratory rate, waist circumfer-

ence, waist/hip ratio, TC, HDL, very low density lipo-

protein, HbA1c, and insulin resistance.58 All studies

find that published RCTs on yoga are small, of short

duration, and heterogeneous, precluding any strong

conclusions on the effectiveness of yoga.

Yoga may provide the same benefits in risk fac-tor reduction as traditional physical activity such as

cycling or brisk walking, supporting a previous narra-

tive review.22 This finding is significant as individ-

uals who cannot or prefer not to perform traditional

aerobic exercise might still achieve similar benefits in

CVD risk reduction. Evidence supports yoga’s accessi-

bility and acceptability to patients with lower physical

tolerance like those with pre-existing cardiac condi-

tions, the elderly, or those with musculoskeletal or

joint pain.28

Lastly, in addition to CVD risk factor improve-

ments, other benefits may result from practicing yoga.For example, yoga may provide health-related quality

of life improvements such as reductions in stress and

anxiety and better coping mechanisms distinct from

other forms of exercise. Yoga may also be practiced

in a variety of settings with no special equipment

needed, potentially increasing the frequency and ease

of practice. These benefits may produce greater willing-

ness to engage in a form of physical activity and better

adherence and sustainability, ultimately facilitating

greater long-term individual- and population-level

CVD and metabolic risk reductions.

Limitations

There are potential limitations of thi

Documents

The Effectiveness of Yoga in Modifying Risk