Work 43 (2012) 133–139
Metabolic syndrome and sleep duration in
Erin C. McCanliesa,∗, James E. Slavena, Lindsay M. Smithb, Michael E. Andrewa, Luenda E. Charlesa,
Cecil M. Burchfielaand John M. Violantic
aBiostatistics and Epidemiology Branch, Health Effects Laboratory Division, National Institute for Occupational
Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV, USA
bDepartment of Psychology, West Virginia University, Morgantown, WV, USA
cSchool of Public Health and Health Professions, Department of Social and Preventive Medicine, State University
of New York at Buffalo, Buffalo, NY, USA
Received 28 June 2010
Accepted 24 November 2010
Abstract. Objectives: To examine associations for sleep quality and quantity with metabolic syndrome (MS) and its five
components in police officers.
Patients or Participants: The study population consisted of 98 randomly selected officers (39 women and 59 men) for whom MS
and sleep data were available.
Methods: Sleep duration (categorized as short < 6 hours, long ? 6 hours) for the past week and quality of sleep were collected
by interviewer-administered questionnaires. MS was assessed using standard criteria. Generalized linear models were used to
assess associations between sleep duration or sleep quality and MS, and the mean number of MS components.
Results: Metabolic syndrome was present in 22.0% and 2.6% of the male and female officers, respectively. Women with short
sleep had a significantly higher mean number of MS components (mean = 1.43) than those with longer sleep (mean = 0.81, p =
0.0316). Officers who stopped breathing during the night had more MS components (mean = 2.43) compared to those who did
not (mean = 1.13, p = 0.0206).
Conclusions: Sleep duration and quality were associated with the mean number of MS components, particularly in women.
Future research should examine these associations prospectively, in a larger cohort, exploring possible gender differences.
Keywords: Short sleep, occupation, sleep quality
sleep, and sleep disturbances, such as sleep apnea and
tion in the circadianrhythmleadingto bothpsycholog-
ical andphysiologicaldisturbances[1–4]. Specifically,
the association between sleep problems and metabolic
regulation indicate that sleep problems may lead to the
∗Address for correspondence: Erin C. McCanlies, Ph.D., NIOSH,
MS: 4050, 1095 Willowdale Rd., Morgantown, WV 26505, USA.
Tel.: +13042856132; Fax: +13042856112; E-mail: EIM4@CDC.
development of metabolic abnormalities and, in turn,
metabolic syndrome (MS) which confers an increased
risk of cardiovascular disease (CVD) [5–8].
ic abnormalities: abdominal obesity, elevated triglyc-
erides, decreased high-density lipoprotein cholesterol
(HDL), high blood pressure, and increased fasting glu-
cose [9,10]. To be diagnosed with MS an individual
must have three of the five abnormalities . Sev-
eral studies have reported associations between sleep
problems and MS [12–15] as well as the individual
obesity, fasting glucose level, and triglyceride level [3,
16]. Karlsson et al.  found that MS components
were more common in both men and women who per-
1051-9815/12/$27.50 2012 – IOS Press and the authors. All rights reserved
134 E.C. McCanlies et al. / Metabolic syndrome and sleep duration in police officers
formed shift work; such shift work may lead to some
MS components such as changes in cholesterol, blood
ual components that comprise MS are also associated
with CVD; the combination of three or more of the
MS components is associated not only with increased
rates of CVD, but also stroke, myocardial infarction,
and all cause mortality [7–9,18,19]. Therefore, indi-
viduals who report sleep problems or who have work
schedules that result in abnormal sleep, such as shift-
Sleep problems leading to MS may be particular-
ly problematic for police officers. Officers report that
overtime and shift work are two of the most difficult
aspects of their jobs . The aim of our study was to
sleep in officers was associated with MS or the mean
number of MS components.
In 1999, 115 police officers were randomly selected
sible 934 to participate in a cross-sectional study. All
officers agreed to participate in the study. Sleep data
and informationabout MS was available on 98 officers
(39 women and 59 men). The Center for Preventive
Medicine, State University of New York at Buffalo,
used in this study have been previouslydescribed .
This study was approved by the State University of
New York at Buffalo’s Internal Review Board and the
National Institute for Occupational Safety and Health
an informed consent.
2.2. Assessment of metabolic syndrome
Presence of MS and MS components was derived
am. MS components included elevated waist circum-
ference (? 102 cm for men, ? 88 cm for women), el-
evated triglycerides (? 150 mg/dL), low HDL choles-
terol (< 40 mg/dL for men, < 50 mg/dL for women),
treatment for diabetes, and elevated blood pressure (?
130/85mmHg) or treatment for hypertension. MS was
consideredpresent if a participant had three or more of
2.3. Assessment of sleep
Sleep quantity and quality were obtained by self-
report. Several of the sleep questions have been pre-
viously validated in the Pittsburgh Sleep Quality Index
questionnaire developed by Buysse et al.  and the
sleep apnea survey used by Maislin et al. . Partic-
ipants reported the average number of hours slept for
the last five weekday nights (Sunday through Thurs-
all durationof sleep hours was calculated by taking the
weighted average. The following shows the formula
used to calculate hours of sleep:
([(average sleep per week )* 5 ) +
(average sleep per weekend * 2)] / 7).
Sleep duration was then categorized as either short
(< 6 hours of sleep) or long (? 6 hours of sleep) for
The sleep surveyused to elicit informationaboutthe
officers’ quality of sleep, consisted of seven questions
that focused on sleep characteristics, sleep behavior,
and daytime functioningand were used in the analysis.
Responses were based on occurrences per week and
ranged from strongly agree (occurrence 5–7 times per
week) to strongly disagree (never/0 times per week),
including a “not applicable” response. All sleep prob-
lems were analyzed as “ever” versus “never,” where
ever consisted of “less than once a week,” “1–2 times a
week,” “3–4 times per week,” “5–7 times a week,” and
never for the response “never”.
2.4. Assessment of covariates
Basic demographic information for each participant
naire and included information on age, sex, educa-
tion and smoking. Officers reported their highest level
of education which ranged from “less than 12 years
of school” to “graduate degree”. Smoking status was
recorded as “current,” “former,” or ”never”.
Statistical methods included univariate analyses,
Poisson regression, t-tests, ANOVA, and ANCOVA
models. Prevalence ratios and 95% confidence inter-
vals were calculated using Poisson regression methods
to determine if either MS or the mean number of MS
components was more prevalent in officers who had
longer sleep duration (? 6 hours).
E.C. McCanlies et al. / Metabolic syndrome and sleep duration in police officers135
Demographic characeristics by hours of sleep fort women and men
< 6 hours
(n = 28)
? 6 hours
(n = 70)
? High school
College < 4 yrs
College 4+ yrs
Sleep (avg hours/wk)
∗Values are mean (Standard Deviation) for continuous variables and
number (%) for categorical variables.
The association between sleep quality and the mean
number of MS components was also examined using
overall main effect tests along with the corresponding
using SAS 9.1.3 (SAS Institute, Cary, NC).
Table 1 shows the basic demographic information
of the officers stratified by < 6 hours of sleep and ?
6 hours of sleep. Officers with fewer than six hours of
sleep (mean age = 39.61, standard deviation = 6.96)
reported on average 4.92 ± 0.6 hours of sleep, while
officers with six or more hours of sleep (mean age =
39.61, standard deviation = 7.82) reported on average
6.95 ± 0.8 hours of sleep. MS was present in 14% of
the overall population (22% of male officers surveyed
and 3% of the females). Seven percent, four percent,
and three percent of the officers had 3, 4, or 5 MS
Fig. 1. Proportions of participants with none, one, two, three, four,
or five metabolic syndrome components.
componentsrespectively(Fig. 1). Among officers who
reported6 hoursof sleep per 24 hourperiod,the preva-
lence of MS was 150% higher than among those who
reported ? 6 hours of sleep (Table 2). Officers who
reported less than six hours of sleep were 70% more
likely to have low HDL cholesterol; although this as-
sociation was attenuated after adjusting for age, sex,
education, and smoking (PR = 1.46; 95% CI = 0.91,
2.35) (Table 2). Upon stratification by sex, this associ-
ation remained statistically significant for female offi-
cers even after adjustments for age, smoking, and ed-
ucation (PR = 3.24; 95% CI = 1.53, 6.90) (data not
Sleep duration was only associated with the mean
number of MS components in female officers not male
officers (Table 3). Those with fewer than six hours
of sleep had significantly more mean MS components
comparedto those with six or more hours (1.30 ± 0.82
vs. 0.52 ± 0.63; p = 0.004). This difference remained
ing (1.43 ± 0.24 vs. 0.81 ± 0.17; p = 0.004).
When sleep quality questions and mean number of
MS components were evaluated, the mean number of
MS components was significantly elevated for those
officers who reported that they “stop breathing during
for age, sex, smoking, and education (2.25 ± 0.53 vs.
1.15 ± 0.16, p = 0.05). After stratification by sex,
this relationshipremainedsignificantin femaleofficers
even after adjusting for age, education, and smoking
(1.96 ± 0.53 vs. 0.58 ± 0.15; p = 0.04) (Figs 2a and
The aim of our research was twofold; first to deter-
mine if MS or MS components were associated with
136 E.C. McCanlies et al. / Metabolic syndrome and sleep duration in police officers
Prevalence ratios and 95% confidence intervals of the metabolic syndrome components by sleep duration
< 6 hours ? 6 hours
< 6 hours ? 6 hours
< 6 hours ? 6 hours
< 6 hours ? 6 hours
< 6 hours ? 6 hours
< 6 hours ? 6 hours
1.31 (0.73, 2.35)
1.39 (0.51, 3.78)
1.07 (0.46, 2.51)
1.56 (0.56, 4.37)
2.50 (0.97, 6.47)
Adjusted for age
1.31 (0.73, 2.35)
1.39 (0.51, 3.78)
1.10 (0.48, 2.53)
1.59 (0.57, 4.41)
2.52 (0.98, 6.49)
Adjusted for age and sex
1.28 (0.73, 2.26)
1.29 (0.48, 3.50)
1.07 (0.44, 2.61)
1.54 (0.58, 4.07)
2.42 (0.95, 6.12)
1.33 (0.74, 2.39)
1.46 (0.91, 2.35)
1.13 (0.44, 2.86)
1.26 (0.44, 3.54)
2.29 (0.81, 6.49)
N = simple prevalence ratios, where original sample size of < 6 is 28 and ? 6 is 70.
∗Indicates a significant Poisson regression prevalence ratio at p = 0.05 level.
∗∗Prevalence rates are adjusted for age, sex, education, and smoking.
∗∗∗Insufficient sample size for the model to run.
E.C. McCanlies et al. / Metabolic syndrome and sleep duration in police officers137
Mean number of metabolic syndrome components by duration of sleep for women and men
< 6 hours
N = 10
1.30 ± 0.82
1.29 ± 0.22
1.43 ± 0.24
N = 18
1.61 ± 1.42
1.63 ± 0.35
1.74 ± 0.40
? 6 hours
N = 29
0.52 ± 0.63
0.52 ± 0.13
0.81 ± 0.17
N = 41
1.44 ± 1.48
1.43 ± 0.23
1.69 ± 0.37
Adjusted for age
Adjusted for age, education, and smoking
Adjusted for age
Adjusted for age, education, and smoking
Values are means ±standard deviation for the unadjusted model, and means ± S.E.for the adjusted models.
∗Indicates significant ANOVA results at an alpha level of 0.05 confidence level.
Fig. 2. (a) Mean number of metabolic syndrome components by indicators of sleep quality for female officers; (b) Mean number of metabolic
syndrome components by indicators of sleep quality for male officers.
duration of sleep, and second to determine if MS or
its components were associated with quality of sleep.
duration of sleep, neither long nor short. This was true
whether the group was evaluated as a whole or if male
officers and female officers were evaluated separately.
However, among female officers who reported short
sleep duration (< 6 hours), the prevalence of low HDL
cholesterol was elevated compared to female officers
male officers we also observed an association between
the mean number of MS components and short sleep.
of association found in men. The relative magnitude
of the mean MS components between men and women
in women. However based on the results it appeared
that the prevalence of MS in women between the two
sleep groupswas drivenby low HDL (data not shown).
To test this we examinedthe association between sleep
duration and number of MS components adjusted for
low HDL. The results confirmed our suspicion and in-
dicated that the association between the number of MS
and duration of sleep is mainly due to an association
between sleep duration and low HDL.
A number of studies have found that sleep prob-
lems such as total number of sleep hours and quality
of sleep are associated with indices of cardiovascular
disease[24–28]. Incontrasttoourfindings,a fewstud-
ies have found that short sleep duration (? 6) was as-
sociated with MS [29,30]. Unlike our study, neither
of these studies stratified by sex nor did they report a
relationship between HDL cholesterol and short sleep.
Hall reportedfindingan associationbetween short
sleep, defined as < 6.99 hours, and increased levels
of abdominal obesity, glucose, and triglycerides .
tension were associated with short sleep (? 5 hours).
Other studies, though not specifically examining MS
or MS components, have found associations between
tors including elevated glucose, triglycerides, abdom-
inal obesity, and blood pressure [24–28,31,32], none
138 E.C. McCanlies et al. / Metabolic syndrome and sleep duration in police officers
of which were significant in our population. However,
in comparison to our study, many of these studies had
fairly large sample sizes.
Besides the duration of sleep per night, there are a
shownto beassociatedwith cardiovasculardisease and
MS. We evaluated seven that included, sleep disturbs
partner, snoring, stops breathing, wake up gasping for
ing the day. Of these, stops breathing was found to be
female officers. Sleep apnea, the conditionin which an
individual stops breathing during sleep, has also been
shown to be associated with indicators of MS such as
glucose intolerance, obesity, and high blood pressure
as well as MS itself [5,12–15,26,33,34]. For example,
Jennings et al.  found a link between overall sleep
intolerance. Coughlin et al.  reported that those
individuals who stopped breathing during sleep were
nearly six times more likely to have MS compared to
those who did not. Contrary to our findings, Sasanabe
et al.  reported that in Japanese participants, “ces-
sation of breathing during sleep” was associated with
MS in men but not women. Differences in our results
compared to what has been reported in the literature
may be due to differencesin sample size, study design,
as well as our unique population.
Although the results of this study are intriguing, this
studyis limited bythe small samplesize. Furthermore,
indicate the direction of causality. Longitudinal analy-
ses may clarify the relationships we reported between
sleep duration and the mean number of MS compo-
nents as well as the relationship between women who
stop breathing during sleep and the mean number of
There are few studies that have evaluated the asso-
ciation of MS with the duration of sleep quantity and
quality of sleep in police officers. It is well known that
policingis a highlystressful occupationandthat dueto
this stress, officers may be at an increased risk of nega-
tive health outcomes such as CVD and MS . Shift
work, long work hours, and lack of sleep may all place
officers at furtherincreasedrisk for poorpsychological
and physical outcomes such as MS . Further re-
search examiningthese associations prospectively,in a
may be worthwhile.
National Institute for Occupational Safety and
The findings and conclusions in this report are those
of the author(s) and do not necessarily represent the
views of the National Institute for Occupational Safety
The data was collected at the State University of
New York at Buffalo, Buffalo, NY. All data analyses
for this manuscript occurred at the National Institute
Conflict of interest
There are no financial conflicts of interest.
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