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Mind- and Body-Based Interventions Improve Glycemic
Control in Patients with Type 2 Diabetes:
A Systematic Review and Meta-Analysis
Fatimata Sanogo, MS,
1,2
Keren Xu, PhD,
1
Victoria K. Cortessis, PhD,
1,3
Marc J. Weigensberg, MD,
2,4
and Richard M. Watanabe, PhD
1,2,5
Abstract
Aims/Hypothesis: Only 51% of patients with type 2 diabetes achieve the hemoglobin A1c (HbA1c) <7%
target. Mind and body practices have been increasingly used to improve glycemic control among patients with
type 2 diabetes, but studies show inconsistent efficacy. The authors conducted a systematic review and meta-
analysis to assess the association between mind and body practices, and mean change in HbA1c and fasting
blood glucose (FBG) in patients with type 2 diabetes.
Methods: The authors conducted a literature search of Ovid MEDLINE, Embase, and ClinicalTrials.gov
seeking through June 10, 2022, published articles on mind and body practices and type 2 diabetes. Two
reviewers independently appraised full text of articles. Only intervention studies were included. Reviewers
extracted data for meta-analysis. Restricted maximum likelihood random-effects modeling was used to cal-
culate the mean differences and summary effect sizes. The authors assessed heterogeneity using Cochran’s Q
and I
2
statistics. Funnel plots were generated for each outcome to gauge publication bias. Weighted linear
models were used to conduct study-level meta-regression analyses of practice frequency.
Results: The authors identified 587 articles with 28 meeting the inclusion criteria. A statistically significant and
clinically relevant mean reduction in HbA1c of -0.84% (95% confidence interval [CI]: -1.10% to -0.58%;
p<0.0001) was estimated. Reduction was observed in all intervention subgroups: mindfulness-based stress re-
duction: -0.48% (95% CI: -0.72% to -0.23%; p=0.03), qigong:-0.66% (95% CI: -1.18% to -0.14%; p=0.01),
and yoga: -1.00% (95% CI: -1.38% to -0.63%; p<0.0001). Meta-regression revealed that for every additional
day of yoga practice per week, the raw mean HbA1c differed by -0.22%(95%CI:-0.44% to -0.003%; p=0.046)
over the study period. FBG significantly improved following mind and body practices, with overall mean dif-
ference of -22.81 mg/dL (95% CI: -33.07 to -12.55 mg/dL; p<0.0001). However, no significant association was
found between the frequency of weekly yoga practice and change in FBG over the study period.
Conclusions/Interpretation: Mind and body practices are strongly associated with improvement in glycemic
control in patients with type 2 diabetes. The overall mean reduction in HbA1c and FBG was clinically
significant, suggesting that mind and body practices may be an effective, complementary nonpharmacological
intervention for type 2 diabetes. Additional analyses revealed that the mean decrease in HbA1c was greater in
studies requiring larger number of yoga practice sessions each week.
1
Department of Population and Public Health Sciences, Keck School of Medicine of USC, Los Angeles, CA, USA.
2
USC Diabetes and Obesity Research Institute, Keck School of Medicine of USC, Los Angeles, CA, USA.
Departments of
3
Obstetrics and Gynecology,
4
Pediatrics, and
5
Physiology and Neuroscience, Keck School of Medicine of
USC, Los Angeles, CA, USA.
JOURNAL OF INTEGRATIVE AND COMPLEMENTARY MEDICINE JICM
Volume 00, Number 00, 2022 pp. 1–11
ªMary Ann Liebert, Inc.
DOI: 10.1089/jicm.2022.0586
1
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Keywords: mind and body practices, complementary medicine, type 2 diabetes, clinical practice, epidemiology
Introduction
Despite the availability of a range of therapies
1,2
to
address the management of hyperglycemia, it is esti-
mated that only 51% of patients with type 2 diabetes achieve
the therapeutic target of hemoglobin A1c (HbA1c) <7%.
3
A
variety of factors, including clinical inertia, polypharmacy,
overly complex medication regimens, socioeconomic status,
health disparities, and psychiatric disorders, are thought to
reduce treatment compliance and efficacy, thus contributing
to inadequate glycemic control.
4
In addition, the prevalence
of diabetes distress, the emotional distress resulting from
living with diabetes and the anxiety associated with daily
self-management, in people with type 2 diabetes is reported
to be 36%
5
and has been shown to be significantly linked to
poor glycemic control
6
and treatment compliance.
More than half of U.S. adults use some form of com-
plementary and alternative medicine (CAM)
7
for health
reasons. Studies have shown that CAM helps a variety of
conditions including relieving stress, improving sleep, de-
creasing chronic pain, and improving mental and emotional
health.
8
According to the National Center for Com-
plementary and Integrative Health, mind and body practices
are a large and diverse subset of CAM procedures and
techniques.
8
The most common mind and body modalities
used in the United States are mindfulness-based stress re-
duction (MBSR) and other forms of meditation, yoga, gui-
ded imagery, and qigong.
7
In the United States, it is
estimated that 66% of patients with type 2 diabetes use mind
and body practices,
9
of whom 6%–20% are using it spe-
cifically to treat their diabetes.
10
Studies have shown inconsistent results regarding the
association between mind and body practices and im-
provements in glycemic control, measured by HbA1c or
fasting blood glucose (FBG), in patients with type 2 dia-
betes.
11,12
In addition, the biological mechanism(s) by
which mind and body practices improve glycemic control
has largely been unexplored. A recent meta-analysis on the
effects of yoga interventions on glycemic control reported
overall improvement reflected by improved HbA1c and
FBG.
13
However, the study also reported high heterogeneity
in the findings with no exploration of factors that could
explain the heterogeneity. This earlier meta-analysis did not
include several experimental studies of yoga that are now
available, and information about the efficacy of other
common modes of mind and body practices on glycemic
control has not, to the best of the authors’ knowledge, been
systematically explored.
The objective of this study was to conduct a systematic
review and meta-analysis to assess whether mind and body
practices (including yoga, qigong, guided imagery, MBSR,
and other forms of meditation) improve glycemic control in
patients with type 2 diabetes.
Materials and Methods
The authors adhered to the Preferred Reporting Items for
Systematic Reviews and Meta-Analysis (PRISMA) guide-
lines, and a detailed protocol is available on Prospero.
14
The
authors applied the population, intervention, comparison,
outcome (PICO) method, defining population as patients
with type 2 diabetes only and intervention as mind and body
interventions that include yoga, qigong, meditation, MBSR,
or guided imagery. The authors distinguish other forms of
meditation from MBSR, the standardized evidence-based
mindfulness training developed by Dr. Jon Kabat Zin and
used in clinical practice.
15
The comparator depended on
study design. In randomized control trials (RCTs), it was
glycemic control in individuals who did not receive the
intervention during the study period, and in matched pre–
post studies, it was glycemic control before the intervention.
The primary outcome of interest was glycemic control as
measured by the mean change in HbA1c, with the mean
change in FBG serving as a secondary outcome of interest.
Data sources and searches
The authors conducted literature search of Ovid MED-
LINE, Embase, and ClinicalTrials.gov seeking all published
articles on common mind and body practices in patients with
type 2 diabetes through June 10, 2022. The authors conducted
separate searches using both controlled vocabulary (MeSH
terms) and keywords, clinically and commonly used terms as
well as definite and possible terms for each of type 2 diabetes,
mind and body practices, and glycemic outcome (FBG and
HbA1c). Results of each search were then intersected using
the Boolean operator ‘‘AND’’ to capture articles relevant to
this systematic review. Additional details, including specific
search terms, can be found in the Supplementary Data.
Inclusion criteria
The authors included only human intervention studies
meeting the PICO criteria, identifying a mind and body
practice intervention, and reporting measures of glycemic
control needed to estimate the raw mean difference for in-
tervention versus comparator groups. Studies were excluded
if they provided incomplete data, reported only median
values of the outcome, included participants with type 1
diabetes or other conditions, or were not available as En-
glish language full-text reports.
Study selection
All citations identified in the search were imported into
Covidence
16
and screened for duplicate entries, which were
removed in accordance with PRISMA guidelines. The re-
maining abstracts were independently reviewed by two
members of the research team to identify those with the
potential to meet the criteria for inclusion. These articles
were reviewed in full by independent reviewers, with criti-
cal appraisal of study quality and to identify those that met
the study inclusion criteria. Disagreements between re-
viewers were resolved by consensus. Publication authors
were contacted to request missing information for studies
that met the inclusion criteria but did not report data needed
for the meta-analysis.
2 SANOGO ET AL.
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Data extraction and quality assessment
Two independent reviewers extracted the data for the
meta-analysis from qualifying reports. Redundant data from
repeated publications were eliminated. Data were extracted
for study design, subject recruitment, sample size for in-
tervention and control groups, intervention type, outcome
assessment, demographic variables, potential confounders,
and mean baseline and follow-up measures of glycemic
control and corresponding standard deviation for each study
group. Data were managed using Research Electronic Data
Capture (REDCap) hosted at the University of Southern
California (Los Angeles, CA).
17
Data synthesis and analysis
The authors performed meta-analysis of the raw mean
differences assuming equal variance as there was no evi-
dence to assume variances are unequal. The primary ad-
vantage of the raw mean difference is that it is inherently
meaningful since the results are reported on a known scale.
Means and standard deviations for the treatment and control
groups were used for RCTs, and the baseline and follow-up
means were used for matched pre–post studies. The standard
correlation of r=0.5 was used to account for the within-
subject correlation between pre- and post-scores for mat-
ched studies.
18
Negative effect sizes indicate participants
who received the intervention improved on measures of
glycemia (i.e., showed reduction in glycemic measures).
The restricted maximum likelihood random-effect model
was used to calculate the weighted means and corresponding
95% confidence intervals (CIs). Estimates for individual stud-
ies and summary estimates were displayed as forest plots
stratified according to specific intervention type. Heterogeneity
was assessed using Cochran’s Qand I
2
statistics.
19
Funnel plots
were generated for each outcome to gauge publication bias.
The authors observed high heterogeneity for the yoga
intervention and subsequently explored the influence of
duration of intervention and frequency of yoga practice
(days/week) on effect size by conducting univariate meta-
regression using data from all included studies, as well as
from the subset of studies that reported on both HbA1c and
FBG. The authors additionally conducted cumulative meta-
analyses ordered on relative study weight (large to small) to
explore the robustness of available data addressing each
outcome by determining the minimum number of studies
needed to achieve statistical significance. Finally, the au-
thors performed a separate meta-analysis of the mean
change in HbA1c stratifying by intervention type (pre–post
studies vs. RCTs) to assess the effect of study design in the
observed heterogeneity. All analyses were conducted using
Stata 16 (College Station, TX).
Results
Figure 1 illustrates the flow of data through the study. The
authors initially identified 587 citations, from which 159
duplicates were detected and removed. Independent review
of titles and abstracts of the remaining 428 reports identified
164 candidates, which potentially met the inclusion criteria.
Critical review of these reports revealed that 71 were not
intervention studies, 17 did not use an intervention of in-
terest, 16 included participants with conditions other than
type 2 diabetes (type 1 diabetes or prediabetes as defined by
the individual study), 14 did not report an outcome measure
of interest, 2 were not available in English, 1 was missing
full text, 1 used combined interventions, 4 lacked relevant
information on participants’ recruitment process and baseline
characteristics, 4 did not provide data needed for meta-
analysis, and 6 reused the same set of data reanalyzed from
studies already included in the meta-analysis.
20–25
FIG. 1. Meta-analysis flow diagram. The meta-analysis flow diagram outlines how the final publications were selected.
Literature search identified 587 studies, and 159 duplicates were detected through Covidence and removed. Two-hundred
and sixty-four studies that did not meet the study inclusion criteria were excluded. The remaining 164 studies were
submitted to a full-text critical appraisal, and a final 28 studies were included in the meta-analysis.
MIND AND BODY INTERVENTIONS IMPROVE GLYCEMIA 3
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Authors of three of the four publications with missing
data who were contacted did not respond to our queries, and
authors of the fourth were unable to provide the measure-
ments of interest. Thus, 28 studies were included in the final
meta-analysis. Studies included used guided imagery (n=1),
MBSR (n=5), meditation (n=1), qigong (n=3), or yoga
(n=18) as the intervention. The single meditation inter-
vention study used Buddhist Walking meditation, which
distinguishes it from MBSR, the standard evidence-based
mindfulness training used in clinical practice.
Included studies, published from 1993 to 2022, are sum-
marized in Table 1. Eighteen studies were RCTs, and 10 were
matched pre–post studies in which values of glycemic mea-
sures were compared for individual participants at time points
before and after the intervention. Seven studies reported on
both the primary (HbA1c) and secondary outcomes (FBG), 8
studies reported on HbA1c alone, and 13 studies reported on
FBG alone. Two studies
26,27
reported results for three inde-
pendent subpopulations, and data for these subpopulations
were analyzed separately and distinguished in this report with
suffixes A, B, and C.
Studies included in the meta-analysis are diverse in sev-
eral ways. Population samples represented a variety of
countries, including Australia, India, the United States,
Germany, South Korea, Cuba, Thailand, China, and Japan,
reflecting a range of race/ethnicity. The duration of inter-
vention ranged from 1 week to 3 years of follow-up, while
the weekly frequency ranged from once per week to daily.
The reported mean age across studies ranged from 42 to 68
years and represented both sexes, except for the study by
Sreedevi et al. that enrolled only females.
28
Participants
were mostly recruited from clinical settings, although a few
studies extended recruitment into the community. Ascer-
tainment schemes varied across studies.
The studies also shared several important features. All ex-
cluded type 2 diabetes patients treated with insulin and those
with medical complications (e.g., coronary artery disease, renal
complications), thereby controlling by restriction for diabetes
complication and duration. Participants in all studies were kept
on their standard medical care, controls in most RCTs received
standard of care only. However, in one study,
29
participants
were randomly assigned to either intervention or a waitlist
Table 1. Characteristics of Studies Included in the Meta-Analysis
Study Location Sample Study type
Intervention details
Type Duration Frequency sessions
Jablon et al.
50
USA 10 c, 10 tx RCT GI 4 weeks Daily
Rosenzweig et al.
51
USA 11 Pre–post MBSR 8 weeks 1 day/week
Kopf et al.
12
Germany 57 c, 53 tx RCT MBSR 3 years 1 day/week
a
Jung et al.
32
South Korea 28 c, 28 tx RCT MBSR 8 weeks 2 days/week
Whitebird et al.
11
USA 31 Pre-post MBSR 8 weeks 1 day/week
Guo et al.
38
China 50 c, 50 tx RCT MBSR 12 weeks Daily
Gainey et al.
35
Thailand 11c, 12 tx RCT Meditation 12 weeks 3 days/week
Tsujiuchi et al.
52
Japan 10 c, 16 tx RCT qigong 4 months 1 day/week
Wang et al.
53
China 20 c, 20 tx Pre–post qigong 4 months Daily
Lam et al.
41
Australia 25 c, 28 tx RCT qigong 6 months 2 times/week
b
Jain et al. (A)
26
India 45 Pre–post Yoga 40 days 2 times/week
Jain et al. (B)
26
India 28 Pre–post Yoga 40 days 2 times/week
Jain et al. (C)
26
India 76 Pre–post yoga 40 days 2 times/week
Gordon et al.
23
Cuba 77 c, 77 tx RCT Yoga 24 weeks 1 day/week
Singh et al.
55
India 30 c, 30 tx RCT Yoga 45 days Daily
Amita et al.
54
India 21 c, 20 tx RCT Yoga 3 months Daily
Hegde et al.
29
India 63 c, 60 tx RCT Yoga 3 months 3 days/week
Beena and Sreekumaran (A)
27
India 37 c, 33 tx RCT Yoga 3 months 6 days/week
Beena and Sreekumaran (B)
27
India 21 c, 26 tx RCT Yoga 3 months 6 days/week
Beena and Sreekumaran (C)
27
India 12 c, 14 tx RCT Yoga 3 months 6 days/week
Vizcaino
42
USA 10 Pre–post Yoga 6 weeks 3 times/week
Popli et al.
43
India 80 Pre–post Yoga 6 months 5 days/week
Rajani et al.
44
India 34c, 34 tx RCT Yoga 6 months 6 days/week
Vinutha et al.
45
India 15 Pre–post Yoga 1 week Daily
c
Mullur and Ames
46
USA 5c, 5 tx RCT Yoga 3 months Daily
Angadi et al.
47
India 52 Pre–post Yoga 6 months Daily
Sreedevi et al.
28
India 38 c, 35 tx RCT Yoga 3 months 2 days/week
Mondal et al.
48
India 10 c, 10 tx RCT Yoga 12 weeks 3 days/week
Vijayakumar et al.
49
India 189 Pre–post Yoga 10 days Daily
Vijayakumar and Kannan
25
India 9 Pre–post Yoga 14 days Daily
Nair et al.
39
India 23 c, 22 tx RCT Yoga 10 weeks 4 days/week
Viswanathan et al.
40
India 150 c, 150 tx RCT Yoga 3 months 5 days/week
Each of these publications are cited in the references.
a
Intervention frequency was 1 day/week for 8 weeks, followed by booster session every 6 months.
b
Intervention was 2 times/week for 3 months, followed by 1 time/week for 3 months.
c
Daily from 5:30 AM to 9 PM.
C, control group; GI, guided imagery; MBSR, mindfulness-based stress reduction; pre–post, matched study; RCT, randomized control
trial; tx, treatment group.
4 SANOGO ET AL.
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group, and the waitlist group served as controls during the
study but received the intervention at completion of the study.
Meta-analysis results for change in HbA1c are shown in
Figure 2a. The overall mean reduction in HbA1c across all
intervention types was -0.84% (95% CI: -1.10% to -0.58%;
p<0.0001). The largest mean reduction in HbA1c was ob-
served in studies in which the intervention was yoga
(-1.00% [95% CI: -1.38% to -0.63%]; p<0.0001), although
reductions in the mean HbA1c were also observed in studies
of MBSR (-0.48% [95% CI: -0.72% to -0.23%]; p=0.03),
qigong (-0.66% [95% CI: -1.18% to -0.14%]; p=0.01), and
meditation (-0.50% [95% CI: -2.54% to 1.54%]; p=0.64).
The funnel plot (Fig. 2b) of studies that reported on change
in the mean HbA1c appeared symmetric and provided no
indication that results reflect publication bias.
Meta-analysis results for the mean change in FBG were co-
nsistent with the mean change in HbA1c (-22.81 mg/dL [95%
CI: -33.07 to -12.55 mg/dL]; p<0.0001; Fig. 3a). The funnel
plot (Fig. 3b) again provided no indication of publication bias.
The authors observed significant heterogeneity of effect size
for HbA1c as reflected in both Cochran’s Qand I
2
.I
2
was
estimated to be 87% for HbA1c. This heterogeneity appeared to
arise from differences among the yoga studies and was not
apparent for the other interventions. A similar heterogeneity
pattern was observed for the mean change in FBG. The authors
attempted to identify the source of this heterogeneity by ex-
ploring the influence of duration of intervention and frequency
of yoga practice (days/week) on effect size. There was no
statistically significant association between duration of inter-
vention and either the mean change in HbA1c or FBG. A sta-
tistically significant inverse association between the number of
yoga sessions per week and the effect size was observed for
HbA1c, but not for FBG (Fig. 4a, b). For every additional day of
yoga practice per week, the raw mean HbA1c differed by
-0.22% (95% CI: -0.44% to -0.003%; p=0.046) over the study
period.
Very similar results were found by limiting meta-regression
to the seven studies that reported on both HbA1c and FBG.
This sensitivity analysis also identified statistically significant
inverse association between the number of yoga sessions per
week and the mean reduction in HbA1c ( p=0.02), but not in
FBG ( p=0.75). In this subset of studies, the raw mean dif-
ference in HbA1c was estimated to decrease by -0.27% (95%
CI: -0.50% to -0.04%; p=0.02) for every additional day of
practice per week (Supplementary Fig. S1). Finally, the au-
thors performed a separate meta-analysis of the mean change
in HbA1c stratifying studies by intervention type (pre–post
studies vs. RCTs) and found moderate heterogeneity in pre–
post studies (60.12%), but high heterogeneity in RCTs
(89.71%). Despite variation in heterogeneity between study
types, the mean change in HbA1c was nearly identical between
study types (-0.84% in RTCs vs. -0.85% in pre–post studies).
Finally, cumulative meta-analyses reveal summary esti-
mates of effects of yoga to be very robust because results for
both HbA1c and FBG require data from only 1 of 9 studies
and 1 of 18 studies, respectively, to achieve statistical sig-
nificance (Fig. 5a, b).
Limitations
There are several limitations of this study. Participants in
the studies included in the meta-analysis were not blinded to
the intervention. However, while lack of blinding may
readily increase the risk of bias in the reporting of subjective
outcomes such as behavior, outcome measures used in this
analysis are objective in nature, making this a minor con-
cern. The authors had to exclude data from four reports that
may have qualified for inclusion despite the efforts to con-
tact the investigators to obtain the required information. In
addition, the authors did not include studies identified in the
gray literature because available information did not allow
them to adequately assess quality of the methodology em-
ployed. It is unlikely these exclusions could have spuriously
created the inverse associations reported here, in light of the
robust nature of the contributing data, reasonably symmet-
rical shape of the funnel plots, and lack of a priori rationale
for excluded studies to differ from those included.
Discussion
The authors identified and synthesized experimental evi-
dence regarding the effects of mind and body practices on
glycemic control among patients with type 2 diabetes. The
28 studies included in this analysis show that taken together,
a range of different mind and body practices significantly
reduced both HbA1c and FBG compared with standard of
care in patients with type 2 diabetes. The overall absolute
estimated decrease of 0.84% in the mean HbA1c is statis-
tically and clinically significant.
30
Hirst et al. estimated a
1.12% decrease in HbA1c in a meta-analysis of 35 trials of
metformin monotherapy of at least 12 weeks duration.
31
By
comparison, the overall effect of mind and body practices
on reduction in the mean HbA1c estimated in this meta-
analysis is 75% that reported for metformin.
Because participants in the studies included in this meta-
analysis received standard of care before and throughout the
studies, and, for the most part were actively treated with
metformin, the observed effect of mind and body practices
appears to represent an additional decrease in the mean
HbA1c beyond the monotherapeutic effect of metformin. This
raises the question of whether mind and body practices could
be useful if initiated early in the course of diabetes therapy
along with conventional lifestyle treatments. It further sug-
gests that mind and body practices may also be an effective
preventive measure in people at risk for type 2 diabetes.
The results of this study evoke the question by what
mechanism may mind and body interventions improve gly-
cemic control. Prior studies have shown significant associa-
tions between diabetes distress and poor glycemic control in
patients with type 2 diabetes.
6
Four studies included in this
meta-analysis reported on various measures of patient stress
obtained using the Patient’s Health Questionnaire,
12
Diabetes
Distress Scale,
11,32
or Perceived Stress Scale.
33
The two
studies reporting specifically on diabetes distress showed a
decrease in both diabetes distress and HbA1c in the inter-
vention group, which is consistent with the prior literature.
One possible theory is that a decrease in psychological distress
followed by increased treatment and regimen compliance may
mediate the effect of mind and body practices on glycemia.
Prior studies have also shown significant associations
between elevated serum cortisol and poor glycemic control
in patients with type 2 diabetes.
34
Two studies included in
the meta-analysis
32,35
reported a significant decrease in se-
rum cortisol and glycemia following intervention. Cortisol
MIND AND BODY INTERVENTIONS IMPROVE GLYCEMIA 5
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FIG. 2. Results of the mean change in HbA1c. (a) The forest plot of change in HbA1c stratified by intervention type. The mean difference in HbA1c was computed as
treatment minus control. The combined result together with heterogeneity statistics was computed for each intervention type and overall across all interventions (overall
p<0.0001). (b) Funnel plot of studies reporting on change in HbA1c. The funnel plot appears symmetrical and shows no significant evidence of publication bias.
6
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FIG. 3. Results of the mean change in FBG. (a) The forest plot summarizes the meta-analysis for the change in the mean FBG stratified by intervention type. The mean
difference in FBG was computed as treatment minus control. The combined result together with heterogeneity statistics was computed for each intervention type and
overall across all interventions (overall p<0.0001). (b) Funnel plot appears symmetrical and shows no significant evidence of publication bias. FBG, fasting blood glucose.
7
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could plausibly mediate the benefit of mind and body
practices on glucose control through reduced inflammation
and a cascade of homeostatic mechanisms that improve lipid
profiles, insulin sensitivity, and glycemia.
36,37
This hy-
pothesis will require additional study.
The primary objective of this study was to identify and
synthesize experimental data on efficacy of common forms
of mind and body practices on glycemic control in patients
with type 2 diabetes, which to the best of the authors’
knowledge has not previously been performed. The results
of this study accord with the findings of a previous meta-
analysis
13
that reported improvement in HbA1c and FBG to
be associated with yoga. However, these investigators did
not consider other forms of mind and body practice, and
they included data from only four of the experimental
studies that contributed to this meta-analysis. In addition,
the previous meta-analysis was based largely on studies
conducted in India, in contrast to the far broader geographic
distribution of source populations contributing to this report.
This is, therefore, the first report providing summary es-
timates of efficacy of mind and body practices on glycemic
control in type 2 diabetes to extend synthesis of human data
beyond yoga. While the summary estimates for other com-
mon types of mind and body practices are similar to those
for yoga, this systematic review established that data for
MBSR, meditation, guided imagery, and qigong are very
limited. These other forms of mind and body practices
warrant further investigation in people with type 2 diabetes
because they may be similarly beneficial in reducing both
diabetes distress and physiological distress and may be more
accessible than yoga to some patients with type 2 diabetes.
In all studies, point estimates of effect of yoga on the
mean change in HbA1c and FBG were consistently nega-
tive, although a degree of heterogeneity was apparent.
Heterogeneity could reflect differing degrees of systematic
error and thus bias between studies or true differences in
effect size. Most studies controlled for a priori potential
confounders through randomization, matching, and/or re-
striction to patients without complications and those treated
without insulin. These measures also make greatly varying
degrees of participation bias unlikely. Nonetheless, differing
degrees of measurement error, and thus information bias,
may have been present in contributing studies. FBG has high
day-to-day variability and is a more variable indicator of
control, compared with HbA1c. The clear inverse associa-
tion between number of yoga sessions per week and effect
size observed for HbA1c, but not for FBG, may reflect true
differences in effect size that were obscured by error in-
herent in measuring glycemic control by FBG.
In this scenario, while heterogeneity in FBG data may be
due largely to bias, heterogeneity in HbA1c data may in part
reflect greater efficacy of more intensive yoga practice. This
interpretation is supported by results of the sensitivity analysis
of the subset of studies that reported on both measures of
glycemic control. These studies revealed a pattern of inverse
association between number of yoga sessions per week and
HbA1c, but not FBG, that is remarkably similar to results from
all studies. This agreement strongly implicates differences in
accuracy of the outcome measure because all study elements
and other data—participants, interventions, and covariate
data—would have been identical in these seven studies.
Other factors that could create true differences in effect
size include the types of yoga practiced. Although some
studies reported the type of yoga used in the protocol, others
did not, so the authors could not address this as a study-level
variable. Finally, differences in ascertainment schemes for
recruitment in clinical settings may have produced study
populations with differing propensity to benefit from yoga. It
is worth noting, for example, that some reports did not
provide a diagram illustrating the process of recruitment and
randomization of participants and therefore do not comply to
current methodological standards of reporting intervention
studies. Additionally, some studies did not report important
details on patient demographics or loss to follow-up.
FIG. 4. (a) Bubble plot of change in HbA1c. The bubble plot shows that the mean change in HbA1c decreases as the
number of weekly yoga practice increases. For every additional day of yoga practice per week, the mean difference in
HbA1c decreases -0.22% (95% CI: -0.44% to -0.003%; p=0.046) over the study period. (b) The bubble plot shows no
relationship between the raw mean change in FBG and the number of weekly yoga practice. For every additional day of
yoga practice per week, the raw mean difference in FBG increases 1.9 mg/dL (95% CI: -3.14 to 6.96 mg/dL; p=0.46) over
the study period.
8 SANOGO ET AL.
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FIG. 5. Cumulative meta-analyses by study weight (large to small) for yoga intervention studies. (a) Results for change in HbA1c, and (b) results for change in FBG. In
both cases, only one study is required to achieve statistical significance.
9
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Conclusions
In conclusion, the authors showed by systematic review
followed by critical appraisal and meta-analysis that mind and
body practices reduce HbA1c and FBG in patients with type 2
diabetes. The overall estimated effect is clinically significant
and suggests that these practices may be an effective, com-
plementary nonpharmacological intervention for type 2 dia-
betes. The results further suggest that early initiation of mind
and body practices along with conventional lifestyle inter-
vention could be useful in mitigating hyperglycemia or an ef-
fective preventive measure in those at risk for type 2 diabetes.
Authors’ Contributions
F.S.: study concept and design, collected the data and
performed the meta-analysis, and drafted the article. V.K.C.:
study concept and design, critically reviewed the analysis
and draft of the article. M.J.W.: study concept and design,
critically reviewed the analysis and draft of the article. K.X.:
collected the data and performed the meta-analysis, criti-
cally reviewed the analysis and draft of the article. R.M.W.:
study concept and design, critically reviewed the analysis
and draft of the article, is the guarantor of this work, has full
access to the data, and takes responsibility for the integrity
of the data and the accuracy of the data analysis.
Author Disclosure Statement
No competing financial interests exist.
Funding Information
F.S. and R.M.W. were, in part, supported by a grant to
R.M.W. (DK-105517).
Supplementary Material
Supplementary Data
Supplementary Figure S1
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Address correspondence to:
Richard M. Watanabe, PhD
Department of Population and Public Health Sciences
Keck School of Medicine of USC
2250 Alcazar Street, CSC-204
Los Angeles, CA 90033
USA
E-mail: rwatanab@usc.edu
MIND AND BODY INTERVENTIONS IMPROVE GLYCEMIA 11
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