Sedentary behaviour and cardiovascular
disease: a review of prospective studies
Earl S Ford* and Carl J Caspersen
Division of Population Health and the Division of Diabetes Translation, National Center for Chronic Disease Prevention and Health
Promotion, Centers for Disease Control and Prevention, Atlanta, GA, USA
*Corresponding author. Centers for Disease Control and Prevention, 4770 Buford Highway, MS K67, Atlanta, GA 30341, USA.
16 April 2012
Background Current estimates from objective accelerometer data suggest that
American adults are sedentary for ?7.7h/day. Historically, seden-
tary behaviour was conceptualized as one end of the physical
activity spectrum but is increasingly being viewed as a behaviour
distinct from physical activity.
Prospective studies examining the associations between screen time
(watching television, watching videos and using a computer) and
sitting time and fatal and non-fatal cardiovascular disease (CVD)
were identified. These prospective studies relied on self-reported
The majority of prospective studies of screen time and sitting time
has shown that greater sedentary time is associated with an
increased risk of fatal and non-fatal CVD. Compared with the
lowest levels of sedentary time, risk estimates ranged up to 1.68
for the highest level of sitting time and 2.25 for the highest level of
screen time after adjustment for a series of covariates, including
measures of physical activity. For six studies of screen time and
CVD, the summary hazard ratio per 2-h increase was 1.17 (95%
CI: 1.13–1.20). For two studies of sitting time, the summary
hazard ratio per 2-h increase was 1.05 (95% CI: 1.01–1.09).
Conclusions Future prospective studies using more objective measures of seden-
tary behaviour might prove helpful in quantifying better the risk
between sedentary behaviour and CVD morbidity and mortality.
This budding science may better shape future guideline develop-
ment as well as clinical and public health interventions to reduce
the amount of sedentary behaviour in modern societies.
Cardiovascular diseases, prospective studies, sedentary lifestyle,
The first Surgeon General’s Report on Physical
Activity and Health in 1996 summarized almost four
decades of epidemiological research on various health
and disease outcomes.1This report marked a critical
developmental milestone in raising the consciousness
about the importance of physical activity in enhancing
the health of Americans for both the public health
community and general public and drew attention
to the enormous public health burden of being the
least active group in a population.
labour-intensive physical activities at work, in the
Published by Oxford University Press on behalf of the International Epidemiological Association 2012.
Advance Access publication 26 May 2012
International Journal of Epidemiology 2012;41:1338–1353
by guest on September 13, 2015
home and for transportation. A recent review of US
studies estimated that mean occupational energy
expenditure may have decreased by 142 calories/day
from 1960–62 to 2003–06 among men.2New inven-
tions, such as television and computers, led to a new
paradigm of recreation that increasingly became
sedentary during leisure time. The increasing popular-
ity of the automobile ushered in an era of declining
research sought to unravel relationships between
energy expenditure and health benefits.3The resulting
physical activity guidelines predicated on this research
were largely oriented towards increasing physical
activity levels in the population rather than reducing
sedentary behaviour, per se.1Most early researchers
regarded time spent in sedentary behaviours during
work, leisure and transportation as part of one end
of a physical activity spectrum. An emerging concep-
tualization views sedentary behaviours as somewhat
distinct from physical activity (Figure 1) and recog-
nizes that, paradoxically, high levels of sedentary
behaviour can coexist with high levels of total
In this review, our primary objective was to examine
the relationship between sedentary behaviour and
cardiovascular morbidity and mortality using pro-
spective observational studies
during the past decade. Our secondary objectives
were to summarize the evolution of epidemiological
thought concerning possible adverse health effects of
sedentary behaviour, present emerging evidence sup-
cardiovascular disease (CVD), illustrate the high
prevalence of sedentary behaviour and review the lim-
ited evidence concerning mechanisms specific to
sedentary behaviour underlying a possible association
Defining sedentary behaviour
Activities having a metabolic expenditure ranging
from 41.0 MET (one MET is resting energy expend-
iture set at 3.5ml of oxygen/kg body mass/min) to
some researchers suggest the range should extend to
2.0 METs.6Alternatively, because the MET value of
quietly standing can be as little as 1.2, some have
proposed that sedentary behaviour should be re-
stricted to non-upright activities.7Hence, definitional
Generally, sleeping has a MET level of ?0.9 MET.8
Other sedentary activities include sitting, reading,
meditating, relaxing, thinking, receiving a massage,
watching television, using a computer, listening to
music or the radio, talking on the telephone, writing
letters, playing cards and riding in a car. Most of
these activities involve basically sitting. However,
tabled MET values for different types of sitting
range from 1.0 to 42.0. Although not synonymous,
sedentary behaviour and sitting clearly overlap.
Sedentary behaviours exist in many contexts: occu-
pation, household, leisure-time and transportation.
METsare considered sedentary,5
Measuring sedentary behaviour
Researchers have used at least four methods to assess
sedentary behaviour. Firstly, in occupational studies,
those using job ratings developed by experts have
crudely categorized workers into some framework.
behaviour from generally brief questionnaires. This
method predominates in more recent prospective stu-
dies of the relationship between sedentary behaviour
and adverse health events.
Thirdly, heart rate monitors can be used to assess
Finally, accelerometers that can objectively assess
sedentary behaviour have advanced greatly with
improved utility and falling unit costs. They have
become increasingly attractive for large population-
based studies, such as recent cycles of the National
Health and Nutrition Examination Survey (NHANES)
of the US population.11–13
Prevalence of sedentary behaviour
Adults in many Western countries spend large parts
of their days being sedentary—up to half of a day for
employed persons.14Nielsen Inc. reported that the
average American in 2010 spent ?35h/week watching
TV, 2h watching time-shifted TV, 20min watching
online videos, 4min watching mobile video and 4h
on the internet.15
Hence, time spent on screen
Figure 1 Traditional (A) and emerging (B) conceptualiza-
tions of the relationships between sedentary behaviour and
physical activity and cardiovascular outcomes
SEDENTARY BEHAVIOUR AND CARDIOVASCULAR DISEASE
by guest on September 13, 2015
viewing was the most common sedentary leisure-time
behaviour.3,16Data from the National Human Activity
Pattern Survey showed that the most common seden-
tary activities, when ranked by the percentage of
waking hours, were driving a car (10.9%), office
work (9.2%), watching television or a movie (8.6%),
performing various activities while sitting quietly
(5.8%), eating (5.3%) and talking to someone in
person or over the phone (3.8%).17When asked,
‘How much time do you usually spend sitting or
reclining on a typical day?’, US adults reported on
equal amounts for men and women, greater amounts
for Whites than for African Americans and Mexican
Americans and increasing amounts with increasing
age (Ford ES, personal observations from NHANES)
(Figure 2). In contrast, accelerometer measurements
revealed average sedentary time to be 7.7h/day, also
with little difference between men and women.13
Australian adults showed that participants were sed-
entary for 57% of the time that an accelerometer was
worn.18If sleeping time is included as sedentary time,
people may average ?75% of the day being seden-
tary.7Regarding transportation, the average one-way
commuting time in USA in 2009 was 25.1min.19
during 2007–08,with nearly
To identify prospective studies of sedentary behaviour
and cardiovascular incidence and mortality, we exe-
cuted a search strategy using the PubMed database
(Supplementary data are available at IJE online).
After reviewing 1304 citations produced by that
search, we reviewed 37 articles in depth. In addition,
we examined the bibliographies of articles that we
reviewed. Studies had tobe prospective,have
incidence or mortality from CVD as an outcome, spe-
cifically assess sedentary behaviour (screen time and
sitting) and be conducted on adults. We limited our
search to publications written in English and did not
contact authors for additional information. At the
conclusion of this process, we were left with nine
studies. Both authors abstracted the following data
elements: author, year of publication, exposure cate-
gories, hazard ratios, 95% confidence intervals (CIs),
number of cardiovascular events and number of
relationships for screen time or sitting time were
performed. For screen time, we used the estimates
of relative risk per 2h of screen time that were pre-
viously calculated.20For newer studies of screen time
and studies of sitting time, we calculated estimated
relative risks per 2h/day of screen time from cate-
gories of sedentary behaviour.21For each study, a
standard error was derived from the CI and a
weight was calculated as the inverse of the variance
(1/SE2). Heterogeneity was assessed with the Q stat-
istic and I.22,23Depending on these statistics, fixed
effect or random effect estimated relative risks were
calculated. Stata 10 was used to conduct the analyses.
A seminal study by Morris et al.24was conducted
using about 31000 employees aged 35–64 years of
the London Transport Executive, who were followed
during 1949–50. When compared with conductors,
bus drivers had about double the age-adjusted rate
of fatal coronary heart disease (CHD), but a similar
rate of non-fatal CHD. This was the first indication
that sedentary behaviour could markedly increase
Minutes per day
Age ≥60 years
Age 40–59 years
Age 20–39 years
Figure 2 Age-adjusted and unadjusted mean time (95% CI) spent in sedentary behaviour per day among adults aged
20 years or older, NHANES 2007–08. The following question was asked about sitting or reclining work, at home or at
school: ‘Include time spent sitting at a desk, sitting with friends, travelling in a car, bus or train, reading, playing cards,
watching television or using a computer. Do not include time spent sleeping. How much time do you/usually spend sitting
or reclining on a typical day?’
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? The Author 2012; all rights reserved. Advance Access publication 12 September 2012
International Journal of Epidemiology 2012;41:1353–1355
Commentary: Too much sitting—a public
1Department of Sport Medicine, Norwegian School of Sport Science, Oslo, Norway and2Medical Research Council Epidemiology
Unit, Institute of Metabolic Science, Addenbrooke’s Hospital, Cambridge, UK
*Corresponding author. Department of Sport Medicine, Norwegian School of Sport Sciences, PO Box 4014, Ulleva ˚l Stadion, 0806
Oslo, Norway. E-mail: Ulf.Ekelund@nih.no
10 July 2012
As exemplified by two articles1,2in this issue of the
journal, there has been an almost exponential interest
in researching the potential detrimental health effects
of sedentary behaviour during the past few years.
Sedentary behaviour is a distinct behaviour, not syn-
onymous with physical inactivity, and defined as ‘any
waking behaviour characterized by an energy expend-
iture 41.5Metabolic Equivalents while in a sitting or
reclining position’.3According to this definition, being
sedentary has two prerequisites: the type of behav-
iour, i.e. sitting or reclining, combined with low
energy expenditure. Although robust secular trend
data on sedentary time are unavailable, it is likely
that population levels of total sedentary time have
increased during the past 50 years, possibly owing
to an increase in occupational- and transport-related
The vast majority of studies examining the health
impact of sedentary time has been observational in
design, and most of these addressed the associations
between TV viewing and health outcomes.1This is not
surprising, as TV viewing constitutes the dominant
leisure time of sedentary behaviour in many de-
veloped countries, including Australia, UK and the
USA. However, TV viewing is a specific sedentary
behaviour and may not be a marker of overall seden-
tary time. In addition, TV viewing may be associated
with a generally unhealthy lifestyle difficult to statis-
tically control for in any observational study.
Ford and Caspersen1reviewed prospective observa-
tional cohort studies that reported on the associations
between total sitting time and TV viewing with fatal
and non-fatal cardiovascular disease (CVD). Total sit-
ting time was consistently associated with increased
risk for fatal and non-fatal CVD diseases in all four
studies included in the review. Similar observations
were also recently reported by van der Ploeg et al.4
who demonstrated an increased risk of all-cause mor-
tality with increased total sitting time, an association
that appeared unaffected by sex, age, body mass
index (BMI) and physical activity levels. The majority
of studies (four of six) in the review by Ford and
Caspersen1also showed that higher amounts of time
spent viewing TV were associated with increased risk
of CVD mortality. The pooled risk ratio was increased
by 17% for each additional 2h in front of the TV,
similar to another recent meta-analysis on this topic.5
In a second contribution in this issue, Stamatakis
et al.2report on the cross-sectional associations be-
by guest on September 13, 2015