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ARTICLE
Associations Between Sedentary Behavior
and Blood Pressure in Young Children
David Martinez-Gomez, BSc; Jared Tucker, MSc; Kate A. Heelan, PhD; Gregory J. Welk, PhD; Joey C. Eisenmann, PhD
Objective:To examine the effect of sedentary behav-
ior on blood pressure (BP) in young children using dif-
ferent indicators of sedentariness.
Design:Cross-sectional study.
Setting:A rural Midwestern US community.
Participants:Children aged 3 to 8 years (N=111).
Intervention:Adiposity was assessed using dual
energy x-ray absorptiometry. Objective measurements
of sedentary activity were obtained from the acceler-
ometers that participants wore continuously for 7
days. Measurements of television (TV) viewing, com-
puter, and screen time (TV ⫹computer) were
obtained via parent report.
Main Outcome Measures:Systolic and diastolic BP.
Results:The sample spent a mean of 5 hours per day in sed-
entary activities, of which 1.5 hours were screen time.
Accelerometer-determined sedentary activity was not sig-
nificantly related to systolic BP or diastolic BP after control-
ling for age, sex, height, and percentage of body fat. How-
ever, TV viewing and screen time, but not computer use, were
positively associated with both systolic BP and diastolic BP
after adjusting for potential confounders. Participants in the
lowest tertile of TV and screen time had significantly lower
levels of systolic and diastolic BP than participants in the up-
per tertile.
Conclusions:Sedentary behaviors, particularly TV view-
ing and screen time, were associated with BP in chil-
dren, independent of body composition. Other factors
that occur during excessive screen time (eg, food con-
sumption) should also be considered in the context of
sedentary behavior and BP development in children.
Arch Pediatr Adolesc Med. 2009;163(8):724-730
THE RECENT SECULAR TREND
in obesity is a major public
health concern.1The clus-
tering of cardiovascular dis-
ease risk factors in over-
weight youth suggests that risks may be
immediate and not just indicative of po-
tential future problems.2The effect of obe-
sity on elevated blood pressure (BP)3,4 is a
specific concern because there is evidence
in favor of tracking BP from childhood into
adulthood.5Although genetic factors are as-
sociated with BP,6-9 a healthy lifestyle—
specifically, diet,10,11 physical activity,12-14
and sleep15—seems to be a relevant con-
tributor to BP levels in children. However,
associations between sedentary behavior
and BP have not been clearly established in
youth,15-18 and no studies have examined
associations in younger children (⬍9 years).
Although often assumed to be correlated,
physical activity and sedentary behavior are
increasingly being viewed as independent
constructs.19 Hamilton and colleagues20
have posited the notion of “physiologic in-
activity,” whereby they differentiated be-
tween too much sitting (physiologic inac-
tivity) and structured exercise (physiologic
exercise). Daily physical inactivity or low
nonexercise activity may be indepen-
dently associated with tangible disease risks.
There is clear evidence of the associa-
tion between adiposity and BP in chil-
dren.21 Given the effects of adiposity on BP
during childhood, attention should be paid
to the adiposity rebound period between
ages 3 and 7 years.22,23 In previous studies,
we have found that adiposity is associated
with BP in 3- to 8-year-old children24 and
that sedentary behaviors were positively as-
sociated with adiposity.25 For these rea-
sons, studies hypothesizing associations be-
tween sedentary behaviors and BP in this
specific period must control for adiposity
to examine the independent influence of
sedentary behaviors on BP.
In most studies, sedentary behavior is
typically identified as time spent watch-
ing television (TV) because it is the most
popular form of media use. Nevertheless,
recommendations for sedentary activity
use the terms of overall media use or screen
time.26 However, results from recent stud-
ies indicate that computer use and video
Author Affiliations:
Department of Kinesiology,
Iowa State University, Ames
(Messrs Martinez-Gomez and
Tucker and Dr Welk);
Immunonutrition Research
Group, Department of
Metabolism and Nutrition,
Institute of Food Science,
Technology, and Nutrition,
Spanish National Research
Council, Madrid, Spain
(Mr Martinez-Gomez); Human
Performance Lab, University
of Nebraska at Kearney
(Dr Heelan); and Departments
of Kinesiology and Pediatrics
and Human Development,
Michigan State University, East
Lansing (Dr Eisenmann).
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game play may have different metabolic and physi-
ologic effects.27 Hence, time spent in TV viewing, com-
puter use, and screen time should be considered inde-
pendently in health-related research. Sedentary behavior
is most typically assessed with proxy reports by par-
ents,28 but objective data can also be obtained using ac-
celerometers.29 The time spent in specific sedentary be-
haviors cannot be determined, but it is possible to measure
low-energy expenditure levels.30
To our knowledge, no studies have examined the as-
sociations between sedentary behavior and BP in young
children using different indicators of sedentariness (ie,
TV watching, computer use, screen time, and objec-
tively assessed time in sedentary activity). Currently, it
is unknown whether sedentary behavior is associated with
higher levels of BP in children during the adiposity re-
bound period. For effective prevention of hypertension
and cardiovascular disease, it is important to better un-
derstand the influence of sedentary behaviors on BP.
Therefore, the purpose of this study was to examine the
associations between sedentary behavior and BP in young
children.
METHODS
PARTICIPANTS
Participants for the current analysis included 57 boys and 54
girls (N=111) aged 3 through 8 years from a rural US commu-
nity in the Midwest (population, 30 000) who completed cor-
rectly assessments of anthropometry, body composition, BP,
and sedentary behavior by accelerometer and parent report. Chil-
dren were recruited from local preschools and elementary
schools through verbal and written advertisements and by word
of mouth. Parental consent and child assent were obtained for
all participants after the study procedures were explained. The
protocol for the present study was approved by the institu-
tional review board of the University of Nebraska at Kearney.
ANTHROPOMETRY
Anthropometric measurements were assessed for each child
using standard procedures. Participants wore light clothing and
removed their shoes before stature and body weight were as-
sessed. Stature was measured to the nearest 0.1 cm using a wall
stadiometer, and body weight was measured to the nearest 0.01
kg using a standard balance beam scale. Body mass index was
calculated as weight in kilograms divided by height in meters
squared.
BODY COMPOSITION
Fat mass was assessed using dual energy x-ray absorptiometry
with a densitometer (DPX-L; Lunar Radiation Corporation,
Madison, Wisconsin). Whole-body scans were performed on
participants while they were wearing light clothing and lying
supine. The Lunar DPX-L densitometer has been well vali-
dated31 and has been used as the criterion measure for a num-
ber of comparisons with field-based methods (eg, body mass
index, bioelectrical impedance, and anthropometry) in young
children.32 To ensure reliability, a phantom calibration was per-
formed before use. Adiposity measurements were determined
using the pediatric medium scan model in the software for the
densitometer (DPX-L, software version 1.5d; Lunar Radiation
Corporation). Body fat variables derived from dual energy x-ray
absoptiometry included percentage of body fat as well as fat mass
and trunk fat mass (in kilograms). The upper trunk was sepa-
rated from the arms by a line from the axilla to the acromion.
The lower trunk was separated from the legs by an oblique line
through the femoral neck.
RESTING BP
Resting BP was measured in accordance with standard proce-
dures and recommendations, as described elsewhere.33 A clini-
cal mercury sphygmomanometer was used in conjunction with
a stethoscope placed over the brachial artery below the bot-
tom edge of the cuff. Appropriate cuff size was determined by
measuring the circumference of the right upper arm at its larg-
est point. Systolic BP (as determined by the first Korotkoff sound)
and diastolic BP (as determined by the fifth Korotkoff sound)
were measured after participants had been seated for 10 min-
utes and with their right arms supported and both feet on the
floor. Three measurements were taken at 1-minute intervals,
and the mean was used for data analysis.
SEDENTARY BEHAVIOR
Objective Assessment
Objective sedentary activity was assessed using an accelerom-
eter (ActiGraph, model 7164; Manufacturing Technology, Inc,
Fort Walton, Florida). The ActiGraph is a small (5.1⫻3.8⫻1.5
cm), lightweight (45 g), and uniaxial accelerometer designed
to detect vertical acceleration ranging in magnitude from 0.05g
to 2.00gwith a frequency response of 0.25 to 2.50 Hz. This moni-
tor has been validated in both field and free-living research34
and has been used to assess activity patterns in numerous stud-
ies.35,36 Instructions were given to both the parent and child re-
garding proper placement and wearing procedures for the ac-
tivity monitor. Specifically, the accelerometers were worn over
the right hip, anterior to the iliac crest, and participants were
asked to wear the monitor at all times with the exception of
sleeping and water activities, such as bathing and swimming.
Participants wore the monitor for 7 consecutive days, after which
the monitors were returned and uploaded using software pro-
vided by the manufacturer. For the current study, 30-second
epochs were used in concordance with the recommendations
for this age group.37
Data were exported into a spreadsheet (Excel; Microsoft Cor-
poration, Redmond, Washington) and then imported into SAS
statistical software, version 9.1 (SAS Institute, Inc, Cary, North
Carolina) for processing. Detailed screening procedures were
used to ensure that the accelerometers were worn as directed
and that the monitors were functioning properly. Specifically,
adherence checks were performed by assessing consecutive miss-
ing data during the hours of typical wear time (9 AM to 7 PM).
A day of monitoring was considered nonadherent if it con-
tained 3 or more 20-minute periods of missing data (0 counts).
Children with complete data for at least 2 weekdays and 1 week-
end day were included in the current study. A cutoff point of
less than 50 counts per 30 seconds was used in this study to
estimate time (in minutes) spent in sedentary activity.38 This
threshold has been shown to capture sedentary activities such
as watching TV, playing video games, painting, sitting, and other
activities with low levels of physical activity.30,38
Parental Report
The average time spent each day (weekdays and weekend days
combined) in screen time (TV, video, computer, and video game
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usage) was assessed from parent-reported values. Time spent
watching TV was defined as minutes spent watching TV, vid-
eotapes, or DVDs. Computer use was defined as minutes spent
using a home computer or video game. Screen time was com-
puted by summing minutes spent in TV viewing and com-
puter use.
STATISTICAL ANALYSIS
Descriptive characteristics are presented as mean (SD). All vari-
ables were checked for normality of distribution. Fat mass mea-
surements and parent-reported sedentary behavior were natu-
ral logarithmically transformed. Differences between boys and
girls were examined by 1-way analysis of variance. In prelimi-
nary analyses, no significant interactions were found between
sex and body fat measurements or sedentary activities; there-
fore, all analyses were conducted with girls and boys together.
Linear associations between body fat measurements and BP were
assessed by partial correlation, controlling for age, sex, and
height. The associations between sedentary variables (objec-
tively measured sedentary activity and parent-reported times
spent in TV viewing, in computer use, and in screen time) and
systolic and diastolic BP were measured by linear regression,
adjusting for age, sex, height, and body fat measurements.
Analysis of covariance, controlling for age, sex, height, and
percentage of body fat, was used to examine differences in sys-
tolic and diastolic BP values stratified by tertiles of sedentary
behavior (low, middle, and high). Bonferroni adjustments for
multiple comparisons were used to examine the differences be-
tween the tertiles. Statistical analyses were performed with SPSS
statistical software, version 14.0 (SPSS Inc, Chicago, Illinois),
with the level of significance set at P⬍.05.
RESULTS
The descriptive characteristics of the total sample and dif-
ferences between girls and boys are shown in Table 1.
There were no significant differences in age, height, weight,
body mass index, and systolic or diastolic BP between girls
and boys. Body fat measurements were significantly higher
among girls than boys. Parental reported screen time ap-
proximated 1.5 hours per day and objectively measured sed-
entary time 5 hours per day. Boys spent significantly more
time using computers than did girls (P=.004). Other sed-
entary activity measurements did not show significant dif-
ferences between girls and boys. The range of values for
sedentary behaviors should be noted.
Partial correlations, controlling for sex, age, and height,
showed positive associations between body fat measurements
and BP. Systolic BP was significantly associated with percent-
age of body fat (r= 0.344; P⬍.001), total fat mass (r=0.245;
P= .01), and trunk fat (r=0.285; P= .003). Diastolic BP was
also significantly associated with percentage of body fat
(r=0.237; P=.01) and trunk fat (r=0.217; P=.02).
The results of the regression analysis are presented in
Table 2. Accelerometer-determined sedentary activity
was not significantly associated with BP. Time spent in
TV viewing was positively associated with both systolic
BP (P=.001) and diastolic BP (P=.02), whereas time spent
using the computer was not significantly associated with
BP values (P=.18 and P=.23, respectively). Screen time
was positively associated with systolic BP (P=.002) but
not with diastolic BP (P=.15). Age, sex, height, and per-
centage of body fat explained 29% of the variation in sys-
tolic BP (adjusted R2=0.29) and 24% in diastolic BP (ad-
justed R2=0.24). Additional analyses using total fat mass
and trunk fat measurements as confounders instead of
percentage of body fat showed similar results (data not
shown).
Systolic BP (F,0.07; P=.94) and diastolic BP (F,1.78;
P=.17) were not significantly different when stratified by
tertiles of objectively measured sedentary activity
(Figure 1). There were significant trends in time spent
in TV viewing, stratified by tertiles for both systolic BP
Table 1. Characteristics of Study Participantsa
All
(N= 111)
Girls
(n= 54)
Boys
(n= 57)
Age, y 6.24 (1.52) 6.23 (1.60) 6.24 (1.48)
Height, m 1.17 (0.11) 1.17 (0.12) 1.18 (0.10)
Weight, kg 22.31 (5.54) 22.29 (5.74) 22.34 (5.40)
BMI 15.87 (1.60) 15.90 (1.56) 15.85 (1.66)
Systolic blood pressure, mm Hg 101.29 (8.70) 101.06 (8.35) 101.52 (9.05)
Diastolic blood pressure, mm Hg 69.29 (7.76) 69.81 (7.79) 68.80 (7.75)
DXA measurements
Body fat, % 24.93 (5.93) 27.36 (5.83) 22.62 (5.08)b
Total fat, kgc5.80 (2.91) 6.59 (3.23) 5.52 (2.34)d
Trunk fat, kgc2.10 (1.30) 2.38 (1.48) 1.83 (1.06)e
Accelerometer-measured sedentary activity, min/d 299.87 (84.17) 295.98 (67.04) 303.56 (98.14)
Parent-reported screen time, min/d
TV viewingc73.84 (69.56) 63.43 (58.67) 83.70 (77.73)
Computer usec20.93 (33.30) 14.27 (30.44) 27.23 (34.89) d
Screen timec94.77 (80.19) 77.71 (69.75) 110.94 (86.50)
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); DXA, dual energy x-ray absorptiometry;
TV, television.
aData are given as the mean (standard deviation).
bP⬍.001.
cValues were transformed (natural log) before analyses, but nontransformed values are presented in this table.
dP⬍.01.
eP⬍.05.
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(F,8.82; P⬍.001) and diastolic BP (F,3.39; P=.04). Sig-
nificant contrasts in systolic and diastolic BP were found
between the lowest tertile and the highest tertile of time
spent watching TV (Figure 2). Values for BP across ter-
tiles of time spent using computers were borderline sig-
nificant for systolic BP (F,3.09; P=.05) and not signifi-
cant for diastolic BP (F,1.20; P=.30) (Figure 2). Systolic
BP (F,6.10; P=.003) but not diastolic BP (F,0.32; P=.72)
was also significantly different across tertiles of screen
time. Analysis of covariance adjusted for confounders also
showed a trend between systolic BP values by tertiles of
screen time (F,6.10; P=.003) but not with diastolic val-
ues (F,0.32; P=.72). Upon individual comparison, a sig-
nificant contrast was found when comparing the lowest
tertile to the highest tertile in diastolic BP (Figure 2). Ter-
tile means, 95% confidence intervals, and ranges of sed-
entary activities measured objectively and via parent re-
port are displayed in Table 3.
COMMENT
The results of this study show that sedentary behavior
was positively associated with BP in young children. More
specifically, TV viewing and screen time (computed by
summing the time spent in TV viewing and computer use)
were associated with BP after controlling for age, sex,
height, and adiposity.
Although previous studies show that sedentary be-
haviors are related to adiposity25,39-43 and adiposity is re-
lated to BP,21,24 this is the first study, to our knowledge,
to examine associations between sedentary behaviors and
BP in children during the adiposity rebound period.
Several similar studies have been conducted in older
children with the same purpose. Guillaume et al16 found
positive associations between TV time and systolic BP in
Table 2. Association Between Blood Pressure and Sedentary Behaviora
Model Predictor Variable
Systolic Blood Pressure, mm Hg Diastolic Blood Pressure, mm Hg
SEM R2PValue SEM R2PValue
1 Sedentary activity 0.064 0.009 0.07 .47 0.030 0.008 0.03 .73
2 Television viewingb0.272 0.365 0.32 .001 0.201 0.346 0.23 .02
3 Computer useb0.117 0.396 0.13 .18 0.108 0.366 0.12 .23
4 Screen timeb0.245 0.372 0.29 .002 0.122 0.355 0.14 .15
aVariables adjusted for sex, age, height, and percentage of body fat.
bValues were transformed (natural log) before analyses.
110
85
90
95
105
100
80
Sedentary Activity
Systolic Blood Pressure, mm Hg
A80
55
60
65
75
70
50
Sedentary Activity
Diastolic Blood Pressure, mm Hg
B
Tertile
Low
Middle
High
Figure 1. Mean systolic (A) and diastolic (B) blood pressure stratified in
tertiles (low, middle, and high) by time spent in sedentary activity, assessed
with an accelerometer. Errors bars represent standard error of the mean.
Data were analyzed by analysis of covariance with Bonferroni adjustment for
sex, age, height, and percentage of body fat.
110
85
90
95
105
100
80
Systolic Blood Pressure, mm Hg
A
80
55
60
65
75
70
50
Television Viewing Computer Use Screen Time
Diastolic Blood Pressure, mm Hg
B
Tertile
Low
Middle
High
∗
†
§
‡
Figure 2. Mean systolic (A) and diastolic blood pressure (B) stratified in
tertiles (low, middle, and high) by time spent watching television, using a
computer, and screen time, assessed by parent report. Errors bars represent
standard error of the mean. Data were analyzed by analysis of covariance
with Bonferroni adjustment for sex, age, height, and percentage of body fat.
*Significantly different from the low tertile (P=.01). †Significantly different
from the low tertile (P=.001). ‡Significantly different from the low tertile
(P=.002). §Significantly different from the low tertile (P= .047).
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6- to 12-year-old Belgium boys but not girls. Likewise,
Ekelund et al17 examined the associations between TV
viewing and metabolic risk in the samples of 9- and 15-
year-old children from the European Youth Heart Study.
The authors did not find significant associations be-
tween time spent watching TV and systolic or diastolic
BP. In contrast, Wells et al15 found that 1 hour per day
of TV viewing was associated with an increase of 0.35
mm Hg in systolic BP and 0.25 mm Hg in diastolic BP
among 10- to 12-year-old Brazilian children. However,
a limitation of these studies is that they did not control
for adiposity. Pardee et al18 found that time spent watch-
ing TV was associated with risk of hypertension in se-
verely obese children, controlling for individual weight
status. However, a longitudinal study also found no as-
sociation between TV viewing in childhood and BP in
adulthood, independent of adiposity.44
The prevalence rates for elevated BP among US chil-
dren have been increasing in recent years.3,4 Effective pre-
vention strategies are clearly needed given the tracking
of BP and the early development of hypertension, obe-
sity, and other cardiovascular disease risk factors in youth.5
Several studies indicate that the heritability of BP is es-
timated to be about 30%.6Although genetics clearly affect
BP, lifestyle also plays an important role in explaining
the remaining variance in resting BP. Diet10,11 and physi-
cal activity12-14 both have been shown to be associated with
hypertension, but special attention is given here to the
physical activity results. In a study of 5500 children from
the United Kingdom aged 11 to 12 years, higher levels
of accelerometry-determined total physical activity and
moderate-to-vigorous physical activity were associated
with lower BP levels.12 Andersen et al13 also found asso-
ciations between accelerometry-determined physical ac-
tivity and systolic and diastolic BP in children from the
European Youth Heart Study. Similarly, a moderate dose-
response relationship was found between physical activ-
ity and BP in a representative sample of US children par-
ticipating in the 2003-2004 National Health and Nutrition
Examination Surveys.14 Recent findings also indicate that
sleep duration is inversely associated with BP in chil-
dren,15 but additional research is needed to confirm these
findings.
Our results indicate that sedentary activity assessed
by accelerometer was not associated with BP. However,
screen time and, more particularly, TV viewing was sig-
nificantly associated with BP, independent of adiposity.
There are several possible explanations for the associa-
tion between TV viewing and BP. First, isolated physi-
cal inactivity watching TV may have direct effects on BP.
Second, isolated unhealthy behaviors that children may
participate in during TV viewing (eg, eating) may indi-
rectly produce the effects on BP. Time spent watching
TV has been associated with behaviors such as in-
creased consumption of high-fat, high-sugar, and salty
foods and decreased consumption of fruits and veg-
etables.45-48 Furthermore, these behaviors are com-
monly associated with adiposity in children and conse-
quently with BP. Third, both inactivity and related
unhealthy behaviors during TV time may produce syn-
ergistic effects on BP. Last, TV viewing may disrupt sleep
hours in children.49 However, these explanations can-
not be directly elucidated from our results.
Besides the possible interactions of diet, sleep dura-
tion, and TV viewing with BP, our findings also suggest
that displacing screen time with even low-intensity physi-
cal activity may be an important preventive factor dur-
ing childhood. Moreover, we observed that participants
in the lowest tertile of TV viewing had significantly lower
systolic and diastolic BP than participants in the upper
tertiles. Participants in the lowest tertile of screen time
were also significantly different in systolic BP than par-
ticipants in the upper tertile of screen time. Participants
in the low-tertile groups spent an average of less than 30
min/d in TV viewing and screen time. Hence, these re-
sults suggest that 30 minute per day of media use may
be a reasonable threshold in young children to prevent
higher levels of BP.
The American Academy of Pediatrics recommends that
parents should limit children’s screen time to no more
than 2 hours per day.26 Our results and those of others
show that young children spend much of their waking
hours in sedentary activities. The youth in our sample
spent an average of 5 hours per day in sedentary activi-
ties, of which 1.5 hours were screen time. Results from
the 1999-2002 National Health and Nutrition Examina-
tion Surveys indicated that 31.4%, 6.1%, and 37.3% of
2- to 5-year-old children spent more than 2 hours per
day in TV viewing, computer use, and screen time, re-
spectively.39 It is worth remembering that the recom-
mendation proposed by the American Academy of Pe-
diatrics only includes sedentary activities related to media
use. In contrast, Corbin and Pangrazi50 recommend lim-
iting extended periods of 2 hours or more of sedentary
activities (whether media use or not) for children, espe-
cially during the daytime. This recommendation is in line
with the idea of the physical inactivity paradigm.20 How-
ever, our findings are limited to screen time, and BP may
be related to diet and sleeping patterns influenced by
screen time, as discussed in the Introduction and the pre-
ceding paragraphs. Nonetheless, reducing sedentary be-
Table 3. Sedentary Activity, TV Viewing, Computer Use,
and Screen Time by Tertile
Tertile Mean (95% CI) Range
Sedentary activity, min/d
Low 224.85 (217.02 to 232.69) 164 to ⬍259
Middle 284.03 (278.30 to 289.77) 259 to ⬍318
High 390.72 (364.31 to 417.13) 318 to 667
TV viewing, min/d
Low 8.57 (4.87 to 12.27) 0 to ⬍30
Middle 63.08 (57.95 to 68.22) 30 to ⬍90
High 155.16 (137.13 to 173.20) 90 to 330
Computer use, min/d
Low 0 . . .
Middle 5.86 (3.10 to 8.61) 0 to ⬍25
High 65.10 (54.75 to 75.45) 25 to 180
Screen time, min/d
Low 10.84 (6.79 to 14.88) 0 to ⬍30
Middle 92.29 (84.32 to 100.26) 30 to ⬍135
High 194.64 (175.99 to 213.50) 135 to 360
Abbreviations: CI, confidence interval; ellipses, not applicable;
TV, television.
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havior is an important and promising strategy to pre-
vent obesity and hypertension in the young. Behavioral
choice theories suggest that reducing sedentary behav-
iors is a way to increase physical activity.51 A current ran-
domized controlled clinical trial examined the effects of
reducing television viewing and computer use on chil-
dren’s adiposity during the adiposity rebound period.52
The results suggested that reducing television viewing
and computer use may have an important role in pre-
venting obesity among 4- to7-year-old children.
The strengths of this study include the use of direct
measures, such as dual energy x-ray absoptiometry, to
evaluate adiposity and to examine sedentary behavior
using several indicators. Field methods to evaluate adi-
posity have significantly underestimated adiposity in
younger children.32 Ideally, these evaluations should be
made using direct measures such as dual energy x-ray
absoptiometry or underwater weighing. On the other
hand, TV viewing is the most common indicator of sed-
entary behavior, although the recommendation from the
American Academy of Pediatrics considers overall me-
dia use. Thus, TV viewing and computer use are gener-
ally summed to obtain screen time. However, metabolic
and physiologic responses, including systolic and dia-
stolic BP values, to video game play among children were
different than time spent watching TV,27 which suggests
that TV viewing and computer use should not be com-
bined exclusively as screen time. Likewise, the new-
generation computer games may promote slight in-
creases in physical activity compared with traditional
sedentary computer games.53 Another strength of this
study was the inclusion of objectively measured time in
sedentary behavior by accelerometer. Sedentary behav-
iors may be defined as “activities that do not increase en-
ergy expenditure substantially above the resting
level.”29(p174) Considering this definition, sedentary be-
havior involves energy expenditure at the level of less than
1.5 metabolic equivalent tasks and includes activities such
as sitting or lying down, regardless of whether screen time
(TV, video games, etc) is occurring. Further research is
warranted to understand the effect of sedentary behav-
ior on health (eg, obesity, cardiovascular disease, and
metabolic syndrome) using this definition.
Our study has 2 limitations that should be considered
when interpreting the results. First, time spent in TV view-
ing and computer use was assessed by parent report. Al-
though parent report is widely used to assess several life-
style indicators in younger children, differences with
objective methods may be large. Recent studies highlight
that parents underestimate their child’s TV time by more
than 3 hours per week compared with an objective method
when the child has a TV in the bedroom and overestimate
television time by 4 hours per week when there is not a
TV in the child’s bedroom.54 Unfortunately, we did not de-
termine whether children had TVs in their bedrooms. Sec-
ond, there is no consensus on the threshold for sedentary
activity using the ActiGraph accelerometer.34 Previous stud-
ies have used different cutoff points in children, and dif-
ferences among published children’s cutoff points have been
described elsewhere.55
In conclusion, the results of this study showed that TV
viewing and screen time were associated with BP indepen-
dent of body composition in children. Given that total ob-
jective sedentary time was not associated with BP, it ap-
pears that other factors, which occur during excessive screen
time, should also be considered in the context of seden-
tary behavior and BP development in children.
Accepted for Publication: February 3, 2009.
Correspondence: Joey C. Eisenmann, PhD, Depart-
ment of Kinesiology, Michigan State University, 3 IM
Sports Cir, East Lansing, MI 48824 (jce@msu.edu).
Author Contributions: Mr Martinez-Gomez and Drs Welk
and Eisenmann had full access to all the data in the study
and take responsibility for the integrity of the data and
the accuracy of the data analysis. Study concept and de-
sign: Heelan and Eisenmann. Acquisition of data: Tucker,
Heelan, and Eisenmann. Analysis and interpretation of data:
Martinez-Gomez, Tucker, Welk, and Eisenmann. Draft-
ing of the manuscript: Martinez-Gomez, Welk, and Eisen-
mann. Critical revision of the manuscript for important in-
tellectual content: Martinez-Gomez, Tucker, Heelan, Welk,
and Eisenmann. Statistical analysis: Martinez-Gomez and
Welk. Obtained funding: Heelan and Eisenmann. Adminis-
trative, technical, and material support: Heelan. Study su-
pervision: Welk and Eisenmann.
Financial Disclosure: None reported.
Funding Support: This work was supported in part by a
York University Faculty of Arts Research Grant, Ameri-
can Heart Association Beginning-Grant-in-Aid No.
0665500Z (Dr Eisenmann), a University of Nebraska at
Kearney Grant (Dr Heelan), and scholarship AP2006-
02464 from the Spanish Ministry of Education and Sci-
ence (Mr Martinez-Gomez).
Additional Information: This research was conducted by
Mr Martinez-Gomez while working at Iowa State Uni-
versity as a visiting scholar.
Additional Contributions: Heather McArel, BSc, Chad
Cook, BSc, Ryan Krueger, BSc, Ashley Scantling, BSc, and
Bryce Abbey, MSc, assisted with data collection.
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