Relationship between body mass index and perceived insufficient sleep among U.S. adults: an analysis of 2008 BRFSS data.

Abstract

Over the past 50 years, the average sleep duration for adults in the United States has decreased while the prevalence of obesity and associated outcomes has increased. The objective of this study was to determine whether perceived insufficient sleep was associated with body mass index (BMI) in a national sample.
We analyzed data from the 2008 Behavioral Risk Factor Surveillance System (BRFSS) survey (N=384,541) in which respondents were asked, "During the past 30 days, for about how many days have you felt you did not get enough rest or sleep?" We divided respondents into six BMI categories and used multivariable linear regression and logistic regression analyses to assess the association between BMI categories and days of insufficient sleep after adjusting for sociodemographic variables, smoking, physical activity, and frequent mental distress.
Adjusted mean days of insufficient sleep ranged from 7.9 (95% confidence interval [CI]: 7.8, 8.0) days for people of normal weight to 10.5 (95% CI: 10.2, 10.9) days for those in the highest weight category (BMI≥40). Days of perceived insufficient sleep followed a linear trend across BMI categories. The likelihood of reporting ≥14 days of insufficient sleep in the previous 30 days was higher for respondents in the highest weight category than for those who were normal weight (34.9% vs. 25.2%; adjusted odds ratio=1.7 (95% CI: 1.5, 1.8]).
Among U.S. adults, days of insufficient rest or sleep strongly correlated with BMI. Sleep sufficiency should be an important consideration in the assessment of the health of overweight and obese people and should be considered by developers of weight-reduction programs.

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RESEARCH ARTICLEOpen Access
Relationship between body mass index and
perceived insufficient sleep among U.S. adults:
an analysis of 2008 BRFSS data
Anne G Wheaton*, Geraldine S Perry, Daniel P Chapman, Lela R McKnight-Eily, Letitia R Presley-Cantrell and
Janet B Croft
Abstract
Background: Over the past 50 years, the average sleep duration for adults in the United States has decreased
while the prevalence of obesity and associated outcomes has increased. The objective of this study was to
determine whether perceived insufficient sleep was associated with body mass index (BMI) in a national sample.
Methods: We analyzed data from the 2008 Behavioral Risk Factor Surveillance System (BRFSS) survey (N = 384,541)
in which respondents were asked, “During the past 30 days, for about how many days have you felt you did not
get enough rest or sleep?” We divided respondents into six BMI categories and used multivariable linear regression
and logistic regression analyses to assess the association between BMI categories and days of insufficient sleep
after adjusting for sociodemographic variables, smoking, physical activity, and frequent mental distress.
Results: Adjusted mean days of insufficient sleep ranged from 7.9 (95% confidence interval [CI]: 7.8, 8.0) days for
people of normal weight to 10.5 (95% CI: 10.2, 10.9) days for those in the highest weight category (BMI ≥ 40). Days
of perceived insufficient sleep followed a linear trend across BMI categories. The likelihood of reporting ≥14 days of
insufficient sleep in the previous 30 days was higher for respondents in the highest weight category than for those
who were normal weight (34.9% vs. 25.2%; adjusted odds ratio = 1.7 (95% CI: 1.5, 1.8]).
Conclusion: Among U.S. adults, days of insufficient rest or sleep strongly correlated with BMI. Sleep sufficiency
should be an important consideration in the assessment of the health of overweight and obese people and should
be considered by developers of weight-reduction programs.
1. Background
Over the past 50 years, the prevalence of obesity among
U.S. adults has nearly tripled from about 13% in 1960-
1962 to 34% in 2007-2008 [1,2]. Obesity is a major risk
factor for many chronic diseases including type 2 dia-
betes, cardiovascular diseases, cancer, and obstructive
sleep apnea [3-6]. As the prevalence of obesity
increased, the percentage of U.S. adults who reported an
average of ≤6 hours of sleep per day also increased,
from 22-23% in 1985 to nearly 30% in 2005-2007 [7,8].
Results from a recent analysis of Behavioral Risk Factor
Surveillance System (BRFSS) data from 2008 showed
that only 30% of U.S. adults felt they had received ade-
quate sleep every night in the previous month and that
more than 10% felt they had received inadequate sleep
every night [9]. Causes of sleep loss other than sleep dis-
orders include lifestyle and occupational factors [10].
Numerous cross-sectional studies have found an inverse
relationship between sleep duration and body mass
index (BMI) [11,12]; however, others have found a U-
shaped association, with a lower BMI among people
averaging 7-8 hours of sleep and a higher BMI among
those with shorter and longer sleep durations [13-15].
These studies relied on subjective reports of sleep dura-
tion, but the CARDIA Sleep Study, which used an
objective measure (wrist actigraphy), also found that
BMI was inversely associated with sleep duration, as
well as with sleep fragmentation [16]. Recent laboratory-
* Correspondence: AWheaton@cdc.gov
Division of Adult and Community Health, National Center for Chronic
Disease Prevention and Health Promotion, Centers for Disease Control and
Prevention, 4770 Buford Highway NE, Mailstop K-67, Atlanta, GA 30041, USA
Wheaton et al. BMC Public Health 2011, 11:295
http://www.biomedcentral.com/1471-2458/11/295
© 2011 Wheaton et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.

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based studies have demonstrated that chronic sleep
restriction may contribute to obesity by decreasing levels
of leptin and increasing levels of ghrelin, hormones
involved in satiety and hunger-promotion, respectively
[17,18].
Results of a previous analysis of 2002 BRFSS data
from 18 states concerning perceived insufficient rest or
sleep showed that the prevalence of obesity (defined as a
BMI ≥ 30) was higher among respondents who reported
≥14 days of insufficient sleep in the previous 30 days
than among those who reported <14 days [19]. To con-
firm and expand on these previous findings showing a
positive association between multiple levels of BMI and
perceived insufficient rest or sleep in a national sample,
we analyzed 2008 BRFSS data and adjusted results for
sociodemographic variables, as well as for smoking, phy-
sical activity, and frequent mental distress.
2. Methods
The BRFSS collects data through annual state-based tel-
ephone surveys of non-institutionalized U.S. civilians
aged ≥18 years. The surveys are conducted in all 50
states, the District of Columbia, and three U.S. terri-
tories (Guam, Puerto Rico, and the Virgin Islands). As
the BRFSS is a public-use dataset, this research was
exempt from review by an institutional review board.
The core questionnaire of the 2008 BRFSS survey,
which was administered to all survey participants,
included the following question, “During the past 30
days, for about how many days have you felt you did
not get enough rest or sleep?”
Survey participants’ BMI was calculated from their
self-reported weight and height (weight [kg]/height
[m2]); and their BMI-based weight classification was
determined on the basis of National Heart, Lung, and
Blood Institute criteria: underweight (BMI < 18.5), nor-
mal weight (BMI = 18.5-24.9), overweight (BMI = 25.0-
29.9), obese class I (BMI = 30.0-34.9), obese class II
(BMI = 35.0-39.9), and obese class III (BMI ≥ 40) [20].
Female survey participants were also asked whether they
were currently pregnant.
In our analysis, we assessed the extent to which two
measures of sleep (mean number of days of insufficient
sleep and prevalence of ≥14 days of insufficient sleep)
were associated with BMI category. We also assessed
the extent to which these measures were associated with
sex, age in years (18-24, 25-34, 35-44, 45-54, 55-64, and
≥65), race/ethnicity (non-Hispanic white, non-Hispanic
black, Hispanic, and non-Hispanic multiracial/other),
education level (less than high school graduate, high
school graduate or GED recipient, some college, and
college graduate), smoking status (current, former, and
never), recent physical activity (yes or no), and frequent
mental distress (yes or no). Current smoking was
defined as having smoked at least 100 cigarettes in one’s
lifetime and now smoking on at least “some days.” For-
mer smoking was defined as having smoked at least 100
cigarettes in one’s lifetime but not currently smoking.
Never smoking was defined as not having smoked at
least 100 cigarettes in one’s lifetime. Any recent physical
activity was defined on the basis of survey participants’
response to the question, “During the past month, other
than your regular job, did you participate in any physical
activities or exercises such as running, calisthenics, golf,
gardening, or walking for exercise?” Frequent mental
distress was defined on the basis of participants’
response to the question, “Now thinking about your
mental health, which includes stress, depression, and
problems with emotions, for how many days during the
past 30 days was your mental health not good?” A
response of ≥14 days in the previous 30 days indicated
frequent mental distress.
We conducted all analyses using SAS-callable
SUDAAN (version 10.0.0, Research Triangle Park, NC)
to account for the complex sampling design of the
BRFSS. We used multivariate linear regression analyses
to calculate mean days of insufficient rest or sleep
adjusted for sex, race/ethnicity, age, education level,
smoking status, recent physical activity, and frequent
mental distress. We used multivariate logistic regression
analyses to calculate the proportion of respondents
reporting ≥14 days of insufficient sleep during the pre-
vious 30 days by BMI category and odds ratios (ORs)
for receiving ≥14 days of insufficient sleep by BMI cate-
gory. All ORs were adjusted for sex, race/ethnicity, age,
education level, smoking status, recent physical activity,
and frequent mental distress.
3. Results
The median response rate to the 2008 BRFSS survey
among all 50 states and the District of Columbia was
53.3% (35.8%-65.9%), based on Council of American
Survey and Research Organizations (CASRO) guidelines,
and the median cooperation rate was 75.0% (59.3%-
87.8%). There were 414,509 respondents to the 2008
BRFSS survey. We excluded from our analysis those
with missing data for age (n = 3,653), BMI (n = 18,677),
or days of inadequate sleep (n = 7,060), as well as
women who indicated they were pregnant, weren’t sure,
or did not respond to a question about their pregnancy
status (n = 3,237). After these exclusions, our study
sample consisted of 384,541 U.S. adults (92.8% of all
2008 BRFSS survey respondents).
Weighted population characteristics are shown in
Table 1. Nearly one-fifth of people were current smo-
kers, and one-quarter reported no leisure-time physical
activity in the previous month. Approximately one-tenth
reported frequent mental distress. Only 1.8% of the
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Table 1 Characteristics of respondents to perceived insufficient sleep question: Behavioral Risk Factor Surveillance
System Survey, 2008.
Characteristicn1
%2
Total
Sex
384,541100.0
Men
Women
150,407
234,134
50.5
49.5
Race/Ethnicity
White, non-Hispanic
Black, non-Hispanic
Hispanic
Other/multiracial3
Age
18-24
25-34
35-44
45-54
55-64
65+
Education Level
<High school diploma
High school diploma or GED
Some college
College graduate
Smoker
Current
Former
Never
Physical Activity in Past Month
No
Yes
Frequent Mental Distress4
No
Yes
BMI Category5
Underweight
Normal weight
Overweight
Obese class I
Obese class II
Obese class III
Days of Insufficient Sleep
0 days
1-13 days
14-29 days
30 days
305,289
29,745
25,255
21,051
68.9
9.8
14.5
6.8
12,794
35,636
57,994
79,775
82,897
115,445
12.2
17.9
19.1
19.3
14.5
17.0
36,522
115,468
102,219
129,838
10.9
28.7
26.7
33.8
65,956
114,800
202,463
18.7
24.6
56.6
104,238
279,924
25.0
75.0
340,634
39,088
89.7
10.4
6,253
131,009
141,082
67,084
24,609
14,504
1.8
35.1
36.4
17.1
6.1
3.5
137,781
148,476
57,931
40,353
30.6
41.5
16.9
11.1
1Unweighted n’s. Categories may not sum to survey total because of missing responses.
2Weighted percentage.
3Asian, Native Hawaiian or Other Pacific Islander, American Indian/Alaska Native, or multiracial.
4Frequent mental distress: Mental health, including stress, depression, and problems with emotions, was not good for ≥14 days in past 30 days.
5BMI categories: underweight (BMI < 18.5), normal weight (18.5 ≤ BMI < 25), overweight (25 ≤ BMI < 30), obese class I (30 ≤ BMI < 35), obese class II (35 ≤ BMI
< 40), obese class III (BMI ≥ 40).
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population was underweight, 35.1% was normal weight,
36.4% was overweight, 17.1% was obese class I, 6.1% was
obese class II, and 3.5% was obese class III. Approxi-
mately 30% reported 0 days of insufficient sleep or rest,
and 11.1% reported getting insufficient rest or sleep all
of the previous 30 days.
Among all adults, the adjusted mean number of insuf-
ficient days of sleep in the previous 30 days was 8.6
(95% CI: 8.5, 8.6) (Table 2). The mean number of days
was higher among women than among men (9.1 and
8.0, respectively [p < 0.05]) and lower among Hispanics
than among members of other racial/ethnic groups. In
Table 2 Perceived insufficient sleep among U.S. adults, aged ≥18 years, by selected characteristics: BRFSS, 2008.
Number of Days (in Past 30 Days)
n1
Mean2
≥14 Days of Insufficient Sleep in Past 30 Days
%2
(95% CI) (95% CI) OR2
(95% CI)
Total
Sex
384,5418.6(8.5-8.6) 27.9(27.6-28.2)
Men
Women
150,407
234,134
8.0
9.1
(7.9-8.1)
(9.0-9.2)
25.9
29.9
(25.4-26.3)
(29.5-30.4)
Referent
1.3(1.2-1.3)
Race/Ethnicity
White, non-Hispanic
Black, non-Hispanic
Hispanic
Other/multiracial3
Age
18-24
25-34
35-44
45-54
55-64
65+
Education Level
<High school diploma
High school diploma or GED
Some college
College graduate
Smoker
Current
Former
Never
Physical Activity in Past Month
No
Yes
Frequent Mental Distress4
No
Yes
BMI Category5
Underweight
Normal weight
Overweight
Obese class I
Obese class II
Obese class III
305,289
29,745
25,255
21,051
8.9
8.5
6.9
8.4
(8.9-9.0)
(8.3-8.8)
(6.6-7.1)
(8.1-8.7)
29.2
27.3
22.3
28.2
(28.8-29.5)
(26.3-28.4)
(21.3-23.3)
(26.9-29.5)
Referent
0.9
0.7
0.9
(0.9-1.0)
(0.6-0.7)
(0.9-1.0)
12,794
35,636
57,994
79,775
82,897
115,445
10.2
10.5
9.7
8.7
7.2
5.0
(9.9-10.5)
(10.3-10.7)
(9.6-9.9)
(8.6-8.8)
(7.1-7.3)
(4.9-5.1)
33.9
35.1
32.1
27.9
23.0
15.4
(32.5-35.4)
(34.2-36.0)
(31.4-32.8)
(27.3-28.4)
(22.5-23.6)
(15.0-15.8)
3.1
3.2
2.8
2.3
1.7
(2.8-3.3)
(3.1-3.4)
(2.7-2.9)
(2.2-2.4)
(1.6-1.8)
Referent
36,522
115,468
102,219
129,838
8.3
8.4
8.8
8.6
(8.1-8.6)
(8.2-8.5)
(8.7-9.0)
(8.5-8.7)
27.3
27.2
29.1
27.5
(26.2-28.4)
(26.7-27.8)
(28.6-29.7)
(27.0-28.1)
1.0
1.0
1.1
(0.9-1.1)
(0.9-1.0)
(1.0-1.1)
Referent
65,956
114,800
202,463
9.9
8.6
8.1
(9.7-10.0)
(8.5-8.7)
(8.0-8.2)
32.7
28.3
26.0
(31.9-33.4)
(27.7-28.9)
(25.6-26.4)
1.4
1.1
(1.4-1.5)
(1.1-1.2)
Referent
104,238
279,924
9.6
8.2
(9.5-9.8)
(8.1-8.3)
32.2
26.4
(31.6-32.8)
(26.1-26.8)
1.4 (1.3-1.4)
Referent
340,634
39,088
7.8
15.6
(7.7-7.8)
(15.4-15.8)
24.5
55.9
(24.2-24.8)
(54.8-56.9)
Referent
4.2(4.0-4.4)
6,253
131,009
141,082
67,084
24,609
14,504
8.6
7.9
8.5
9.3
9.7
10.5
(8.0-9.2)
(7.8-8.0)
(8.4-8.6)
(9.1-9.5)
(9.4-10.0)
(10.2-10.9)
27.6
25.2
27.6
30.8
32.3
34.9
(25.2-30.0)
(24.7-25.7)
(27.1-28.1)
(30.1-31.6)
(31.1-33.5)
(33.3-36.5)
1.1(1.0-1.3)
Referent
1.1
1.4
1.5
1.7
(1.1-1.2)
(1.3-1.4)
(1.4-1.6)
(1.5-1.8)
1Unweighted n’s.
2Weighted means, proportions, and odds ratios adjusted for all other variables in the table.
3Asian, Native Hawaiian or Other Pacific Islander, American Indian/Alaska Native, or multiracial.
4Frequent mental distress: Mental health, including stress, depression, and problems with emotions, was not good for ≥14 days in past 30 days.
5Underweight (BMI < 18.5), normal weight (18.5 ≤ BMI < 25), overweight (25 ≤ BMI < 30), obese class I (30 ≤ BMI < 35), obese class II (35 ≤ BMI < 40), obese
class III (BMI ≥ 40).
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general, age was inversely associated with days of insuffi-
cient sleep, with adults aged 18-34 reporting the most
days of insufficient sleep, and those aged 65 or older
reporting the fewest. The mean number of days of insuf-
ficient sleep ranged from 8.3 days among individuals
without a high school diploma to 8.8 days among those
with some college; was higher among current smokers
than among nonsmokers; and higher among people who
reported no leisure-time physical activity in the previous
month than among those who reported at least some
such activity. The mean number of days of insufficient
sleep was 15.6 days among adults who reported frequent
mental distress, compared to 7.8 days for adults without
frequent mental distress.
Overall, 27.9% of adults reported ≥14 days of insuffi-
cient sleep in the previous 30 days (Table 2). The per-
centage who did so was higher among women than
among men (29.9% vs. 25.9%, p < 0.05); lower among
Hispanics than among members of the other racial/
ethnic groups; lower among those aged 65 or older
(15.4%) than among those aged 25-34 (35.1%); higher
among those with some college education; lower
among never smokers than among former smokers and
current smokers (26.0% vs. 28.3% and 32.7%, respec-
tively, p < 0.05); and higher among those who reported
no leisure-time physical activity in the previous month
than among those who reported some such activity
(32.2% vs. 26.4%, p < 0.05). More than half of adults
who reported frequent mental distress also reported
≥14 days of insufficient sleep in the previous 30 days,
compared to about a quarter of adults without fre-
quent mental distress.
When adjusted for sociodemographic characteristics,
smoking status, recent physical activity, and frequent
mental distress, the mean number of days of insufficient
sleep ranged from 7.9 (95% CI, 7.8, 8.0) for people in
the normal-weight category to 10.5 (95% CI, 10.2, 10.9)
for those in the obese class III category. The mean
number was also higher for people who were under-
weight (8.6 [95% CI, 8.0, 9.2]) than for those of normal
weight. A quarter of normal-weight people reported ≥14
days of insufficient sleep in the previous month, com-
pared with 34.9% of those in the obese class III
category.
We observed a clear, positive gradient relationship
between days of insufficient sleep and BMI-based
weight categories from normal weight through obese
class III among both men and women (Figure 1), all
racial/ethnic groups (Figure 2), and all age groups (Fig-
ure 3). Although the number of days of insufficient
sleep was generally higher among people in the under-
weight category than among those in the normal-
weight category, the difference was not always statisti-
cally significant.
3. Discussion
Most studies that have assessed the association between
BMI and sleep have used self-reported usual sleep dura-
tion as their sleep measure. As noted previously, results
from many of these studies have shown a simple inverse
relationship between sleep duration and BMI, whereas
results from others have shown a U-shaped relationship,
with a higher BMI associated with both short and long
sleep durations [21-23]. Other study results have shown
increased morbidity and mortality risk among people
reporting either short or long sleep durations [24-27].
We detected a strong association between days of insuf-
ficient sleep and BMI category except among people
classified as underweight. A likely explanation for this
exception to our overall finding is that the prevalence of
conditions that both cause weight loss and disrupt sleep,
Figure 1 Mean (±95% confidence intervals) days of perceived
insufficient sleep in previous 30 days by BMI category and sex.
Means adjusted for race, age, education, smoking, recent physical
activity, and frequent mental distress.
Figure 2 Mean (±95% confidence intervals) days of perceived
insufficient sleep in previous 30 days by BMI category and
race/ethnicity. Means adjusted for sex, age, education, smoking,
recent physical activity, and frequent mental distress.
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