Sleep and Breathing
https://doi.org/10.1007/s11325-020-02240-9

EPIDEMIOLOGY • ORIGINAL ARTICLE

The association of Sudarshan Kriya Yoga frequency with sleep
quality: a cross-sectional study from Singapore
Robert A. Sloan 1

&

Divya Kanchibhotla 2

Received: 21 August 2020 / Revised: 25 October 2020 / Accepted: 31 October 2020
# Springer Nature Switzerland AG 2020

Abstract
Purpose There is a dearth of evidence for the relationship between yogic breathing and sleep quality. Even less is known about
practice frequency and benefit. We investigated the association of Sudarshan Kriya Yoga frequency with sleep quality amongst
adult practitioners.
Methods In a cross-sectional investigation on adult practitioners of Sudarshan Kriya Yoga in Singapore, the Pittsburgh Sleep Quality
Index (PSQI) was used to assess sleep quality. Sleep quality was examined across three categories of practice frequency (monthly,
weekly, daily). A multivariate logistic regression model was used to determine association.
Results Of 385 adults (241 women), the mean age (SD) was 42.5 (9.9) years. In total, 32% of the sample (n = 124) was identified
as having poor SQ. After adjusting for study covariates, independent analyses revealed an inverse association for higher
frequency of practice and lower odds of poor SQ (OR = 0.52; 95% CI = 0.28–0.94). The p for trend was 0.03.
Conclusion The practice of yogic breathing may benefit sleep quality. Further experimental investigations are warranted.
Keywords Sudarshan Kriya Yoga . Breathing exercises . Sleep quality . Observational . Asia

Introduction
Sleep is a modifiable health behavior associated with morbidity, mortality, and quality of life [1–3]. Emerging evidence
suggests that sleep quality (SQ) may be critical to public
health, and the World Health Organization recently asserted
that poor SQ might be a growing epidemic [2, 4–6]. SQ encompasses the perception of one’s whole sleep experience
(i.e., duration, disturbance, latency), and recent investigations
in the Asian city-state of Sing; apore have shown poor SQ to be
a pervasive health problem in adult populations [3, 7, 8]. One
potential mechanism linked to poor SQ is the chronic activation of the sympathetic nervous system attributed to modern
stressors (i.e., light pollution, digital media, sedentary lifestyle, diet) [4, 9, 10]. Given the collective and ubiquitous

* Robert A. Sloan
rsloan@m.kufm.kagoshima-u.ac.jp; https://orcid.org/0000-00016492-8623
1

Kagoshima University Graduate School of Medical Sciences, 8-35-1
Sakuragaoka, Kagoshima 890-8520, Japan

2

Sri Sri Institute for Advanced Research, Bangalore, India

nature of modern stressors, accessible intervention strategies
may be useful for promoting better SQ [3, 7, 9, 10].
Bin recently asserted that interventions to improve SQ
might help most individuals but to varying degrees [4]. This
view was broadly supported in a systematic review that concluded that some mind-body interventions (i.e., Yoga, Tai
Chi, Qigong, mindfulness) might improve SQ in some adults
[10]. The review was challenging to conduct because of the
numerous types and practice frequencies of mind-body interventions. Due to the lack of investigations, the review was not
able to include evidence regarding yogic breathing exercises
(Prāṇāyāma) despite its high use amongst adults with sleep
problems [10, 11].
Yogic breathing has been suggested as a possible treatment
for patients with insomnia/sleep disorders because it reduces
sympathetic tone and improves parasympathetic activity
resulting in relaxation [9, 12, 13]. Though there are many
types of breathing exercises, Sudarshan Kriya Yoga (SKY)
is the only form that has evidenced-based clinical recommendations (30 min/day) as a treatment modality for stress, anxiety, and depression [14]. SKY is a yoga method that uses a
combined series of self-regulated yogic breathing techniques
and meditation without physical postures/exercise (asanas)
while seated upright [14].

Sleep Breath

Agte et al. found that practicing SKY for 30 min/day for
8 weeks significantly reduced anxiety more than once weekly
in adult practitioners [15]. Although there is evidence for SKY
and mental health association, research for the relationship
between SKY and SQ is lacking. To date, only one investigation has been conducted on SKY and sleep. Sulekha et al.
found that daily SKY practice was associated with some objective markers of better sleep in middle-aged men [16]. To
date, no investigations have compared the frequency of SKY
practice with SQ in men and women. Although sleep medicine researchers have recently discussed yogic breathing’s potential to improve SQ, there is a dearth of evidence [12, 17].
Therefore, this cross-sectional study aimed to determine
the association of SKY with SQ across different practice
frequencies.

From the available survey, we classified SKY practitioners
into the following three categories, occasional (≤ 1/month),
weekly (1–3 days/week), and daily (≥ 5 days/week)
practitioners.

Pittsburgh Sleep Quality Index
The PSQI has been validated across a broad range of populations. The PSQI contains seven components reflected over a
4-week interval: subjective sleep quality, latency, duration,
efficiency, disturbances, medication, and daytime dysfunction. Nineteen questions rated on a 4-point Likert scale are
used to determine the PSQI global score ranging from 0~21
points. A PSQI global score > 5 is the universal marker for
poor SQ [19].

Methods

Covariates

De-identified secondary data were obtained from a health and
wellness survey conducted by the Art of Living Foundation
and the Sri Sri Institute for Advanced Research in Singapore.
Singapore is a cosmopolitan island city-state located in the
southeast region of Asia. The Art of Living Foundation is a
nonprofit humanitarian and educational organization that provides community capacity building for SKY programs
throughout Singapore and globally.
SKY practice sessions are commonly held at community
centers, worksites, universities, and households. The survey
was conducted by convenience sampling before the start of a
SKY practice session from July 2019~November 2019.
Participation in the survey was voluntary, and informed consent was obtained from respondents. The Institutional Review
Board of the Sri Sri Institute for Advanced Research ethics
committee in India approved this cross-sectional study. Once
engaged, the survey was explained to the practitioners, and
consent was obtained to complete a brief paper-based or online survey. All participants were English speaking. Inclusion
criteria for SKY practitioners were if they previously completed an official SKY course provided by the Art of Living
Foundation and had participated in at least one SKY session
within the past 6 weeks. Overall, a total of 385 practitioners
completed the survey.

Study covariates included self-reported age (continuous), gender (male or female), ethnicity (Indian, other), marital status
(married, divorced, widowed, or single), education (graduate
school or not), current smoker (yes or no), drinks alcohol (yes
or no), stress (high or < high), and self-rated health (≥ good or
< good). Self-rated health is a valid measure of general health
status and consists of a single question rated on a Likert scale
[20]. Less than good ratings have been found as significantly
associated with a higher likelihood of chronic disease, health
care utilization, and physical and mental decline [20]. The
stress level was determined by using the Personal Stress Scale
(PSS). The PSS uses ten 5-point Likert scale questions about
feelings and thoughts experienced in the most recent 4 weeks to
determine a summary score ranging between 0~40. Global
scores, ≥ 27, indicated high stress [21]. Body mass index categorization was based on the World Health Organization report
for Asians (< 23, 23–26.9, ≥ 27 kg/m2) [22].

Sudarshan Kriya Yoga
SKY is a method of cyclical and rhythmic breathing practice
aimed at promoting calmness that takes ~ 30 min per session
[14]. SKY practice consists of four distinct yogic breathing
stages that use a range of slow, moderate, and fast breaths per
minute. A SKY session is done in an upright seated posture,
with closed eyes during practice. A more extensive description of SKY can be found in previous publications [14, 18].

Analysis
Descriptive statistics were calculated for study variables.
Logistic regression was used to calculate odds ratios (OR)
and 95% confidence intervals (CI). SKY practice frequency
was divided into three participation groups: occasionally
(referent), weekly, and daily. Odds ratios were provided
for three models (unadjusted, age-adjusted, and multivariate-adjusted). The multivariate model adjusted for age and
all covariates. p < 0.05 was considered statistically significant. The post hoc power analysis was performed to justify
the sample size for this secondary data analysis. Based on
the observed OR = 0.52 of reporting poor SQ amongst daily
practitioners when compared to infrequent practitioners, it
was estimated that the sample size of 385 was sufficient to

Sleep Breath

achieve approximately 90% statistical power at an alpha
level of 0.05.
The Statistical Package for Social Science (version 18.0)
was used for statistical analysis (SPSS, Inc., Chicago, IL,
USA).

Results
The demographic characteristics of the study sample are presented in Table 1. Descriptive statistics of PSQI components
Table 1

Demographic characteristics of the participants
PSQI
Good SQ

Poor SQ

p value*

385

261 (67.8)

124 (32.2)

< 0.001

299 (77.7)
86 (22.3)

204 (78.2)
57 (21.8)

95 (76.6)
29 (23.4)

0.71

144 (37.4)
241 (62.6)

100 (38.3)
161 (61.7)

44 (35.5)
80 (64.5)

0.69

225 (86.20)
36 (13.8)

102 (82.3)
22 (17.7)

0.17

216 (82.8)
45 (17.2)

102 (82.3)
22 (17.7)

0.08

214 (82.0)
47 (18.0)

97 (78.2)
27 (21.8)

0.27

227 (87.0)
34 (13.0)

96 (77.4)
28 (22.6)

0.14

5 (1.9)
256 (98.1)

4 (3.2)
120 (96.8)

0.10

87 (33.3)
108 (41.4)

48 (38.7)
47 (37.9)

0.86

155 (40.3)
95 (24.7)

66 (25.3)

29 (23.4)

115 (29.9)
270 (70.1)

73 (28.0)
188 (72.0)

42 (33.9)
82 (66.1)

Total
N (%)
Age n (%)
< 50 years
≥ 50 years
Gender n (%)
Male
Female

Discussion

Ethnicity n (%)
Indian
327 (84.9)
Others
58 (15.1)
Marital status n (%)
Married
318 (82.6)
Unmarried
67 (17.4)
Education n (%)
Grad and above 311 (80.8)
Others
74 (19.2)
Self-reported health n (%)
≥ Good
323 (83.9)
< Good
62 (16.1)
High stress n (%)
Yes
9 (2.3)
No
376 (97.7)
BMI n (%)
< 23 kg/m2
135 (35.1)
23–26.99 kg/m2
≥ 27 kg/m2
Alcohol n (%)
Yes
No
Smoker n (%)
Yes
No

and frequency of SKY practice are available in Table 2. The
mean age was 42.5 ± 9.9 and the age range was 19 to 76 years
old. The majority of practitioners were of East Indian ethnicity
(~ 85%) and reported being in good health (~ 85%). The prevalence of poor SQ in our sample was ~ 32% (N = 124). Table 3
presents the unadjusted, age-adjusted, and multivariateadjusted ORs and 95% CIs estimating independent associations for SKY practice frequency and the likelihood of poor
SQ. The results showed that weekly practice compared to
occasional practice was not significantly associated with lower odds of poor SQ. The daily SKY group had lower odds of
poor SQ (unadjusted OR = 0.46, 95% CI = 0.26–0.80) compared to the occasional practitioner group. After adjusting for
all study covariates, individuals in the daily SKY group maintained significantly lower odds of poor SQ (OR = 0.52; 95%
CI = 0.28–0.94). Overall, the magnitude and direction (p =
0.03) of the post hoc trend analysis indicated an inverse association for a higher frequency of SKY practice and a lower
likelihood of poor SQ.

5 (1.9)
256 (98.1)

Table 2

Descriptive statistics of PSQI (N = 385)
Total

p value

(PSQI)a
Good SQ

Poor SQ

0.52 (0.65)
0.91 (0.45)
0.61 (0.71)
0.63 (0.61)
0 (0.04)
0.05 (0.22)
0 (0.04)
2.73 (1.28)

1.48 (0.9)
1.37 (0.51)
1.84 (0.9)
1.37 (0.72)
0.12 (0.59)
0.62 (0.6)
0.14 (0.43)
6.94 (1.34)

PSQI componentsa

0.08
0.01

12 (3.1)
373 (96.9)

This study aimed to examine the association of the frequency
of SKY practice with SQ amongst adults in Singapore. After
adjusting for possible confounding variables, we found that
daily SKY practice was independently associated with lower
odds of poor SQ. Also, the trend analysis shows a possible
dose-response association. The findings for daily SKY

7 (5.6)
117 (94.4)

Duration
0.65 (0.76)
Disturbance
0.97 (0.48)
Latency
0.77 (0.84)
Dysfunction
0.73 (0.67)
Efficiency
0.02 (0.22)
Quality
0.13 (0.36)
Medication
0.02 (0.17)
Total PSQI scores 3.29 (1.92)
Sudarshan Kriya Yoga (SKY)b
Occasionally
98
Weekly
145
Daily
142

59 (60.2%)
93 (64.1%)
109 (76.7%)

< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001

39 (39.8%)
52 (35.9%)
33 (23.3%)

a

p value based on one-way ANOVA; *p < 0.05 considered significance

The score range of PSQI components was from 0 (better) to 3 (worse)
and total PSQI scores ranged from 0 (better) to 21 (worse)

PSQI, Pittsburgh Sleep Quality Index; SQ, sleep quality; BMI, body mass
index

b
The practice groups of SKY were created based on occasionally(≤ 1/
month), weekly (1–3/week), and daily (≥ 5days/week)

Sleep Breath
Table 3 Independent association
of SKY with poor sleep quality

Frequency of SKY

Infrequently

Weekly

Daily

p for trend

N = 385
Poor sleep quality n (%)
Unadjusted OR (95% CI)
Age adjusted OR (95% CI)
Multivariate OR* (95% CI)

98
39 (39.8)
1.00
1.00
1.00

145
52 (35.9)
0.85 (0.50–1.43)
0.84 (0.49–1.42)
0.87 (0.49–1.49)

142
33 (23.3)
0.46 (0.26–0.80)
0.45 (0.26–0.79)
0.52 (0.28–0.94)

0.01
0.01
0.03

OR, odds ratio; CI, confidence interval. Values are odds ratios and 95% confidence intervals estimated from
logistic regression models predicting the likelihood of having poor sleep quality
*Adjusted for age, gender, ethnic group, marital status, education, BMI, smoker, alcohol, stress, and self-reported
health

practice are in line with previous mental health clinical treatment recommendations [14]. To the best of our knowledge,
this is the first study to report the inverse relationship between
SKY and poor SQ in a moderately sized adult population.
Our findings are broadly in accordance with the limited
literature available on SKY/breathing exercises with SQ. In
a sleep laboratory study of men (N = 26) aged 31 to 55, it was
found that daily SKY practitioners retained better slow-wave
sleep and reached rapid eye movement in a shorter time than
the control group [16]. Comparably, we found that daily practice was associated with reducing subjectively measured poor
SQ in a larger population of adults across a broad age range
and an array of confounders.
The limited evidence for the effectiveness of breathing exercises on SQ in clinical populations also supports our findings. Two recent experimental studies used the same overall
SQ outcome measured by PSQI as we did. It was found that
newly pregnant women suffering from poor SQ who practiced
2 weeks of daily yogic breathing exercises improved their
overall SQ score by 4.4 points [23]. Similarly, overall SQ
scores improved by 3.4 points after a 4-week yogic breathing
intervention in patients with chronic obstructive pulmonary
disease [24]. Lastly, Tsai et al. found that when insomniacs
did slow-paced breathing for 20 min before bedtime, objectively measured SQ components significantly improved (i.e.,
latency, efficiency, awakenings) [25].
While the mechanisms for the relationship between SKY
and SQ require further investigation, evidence suggests that
SKY practice may induce vagus nerve stimulation, resulting
in a calming effect [18]. Enhanced vagal activity from yogic
breathing normalizes sympathetic nervous system activity and
increases parasympathetic nervous system tone marked by
increased heart rate variability [25, 26]. SKY has also been
shown to reduce cortisol and adrenocorticotropic hormone
levels related to stress reduction [27]. Concomitantly, sleep
medicine researchers have asserted that regular practice of
yogic breathing may improve SQ because it may mimic some
of the enhancements (lung capacity, respiratory function, upper airway patency) provided by continuous positive airway

pressure treatment [13, 17]. From our investigation and the
limited literature, it is unclear if SKY’s effects occur from
acute or chronic practice. To what extent temporality plays a
role is also unclear.

Limitations
This investigation’s primary limitation is that it was a crosssectional study; therefore, we cannot determine causation or
rule out a bidirectional association. Second, we used convenience sampling to observe a multiethnic Asian population;
therefore, these results’ generalizability may be limited.
Lastly, we cannot rule out the potential for recall bias because
of the self-report method.

Conclusion
Our findings show that daily SKY practice is associated with
better SQ. Concurrently; we found that as SKY practice days
increase, the risk of poor SQ decreases. Further experimental
studies should examine the impact of SKY with SQ. Basic
research should be conducted to understand better SKY’s role
and its components with causal mechanisms of better sleep.
Acknowledgments We would like to thank Mr. Manish Doshi, Ms.
Lalita Bajwa, and Ms. Suman Balani from Singapore for their support
for the data collection.
Code availability Not applicable
Authors’ contributions RS contributed in the conception, design, statistical analysis, and manuscript drafting. DK contributed to the data collection
and manuscript editing.
Funding The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Mr.
KM Yee of Singapore supports this work.
Data availability The data that support the findings of this study are
available from the Sri Sri Institute for Advanced Research in Singapore

Sleep Breath
but restrictions apply to the availability of these data, which were used
under license for the current study, and so are not publicly available.

Compliance with ethical standards

11.

12.

Conflict of interest The authors declare that they have no conflicts of
interest.

13.

Ethics approval The Institutional Review Board of the Sri Sri Institute
for Advanced Research ethics committee in India approved this crosssectional study.

14.

Consent to participate and consent for publication Survey participants
gave consent for de-identified use of data and publication of results.

15.

16.

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