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| Journal of the New Zealand Medical Association,
01-April-2005, Vol 118 No 1212
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SIT (seated immobility thromboembolism) syndrome: a
21st century lifestyle hazard
Richard Beasley, Patricia Heuser, Nigel Raymond
The risk of developing VTE following sitting for prolonged
periods at a computer (termed ‘eThrombosis’) has recently been
recognised.1 This report generated considerable
interest and raised several related issues—including whether this case was
an isolated event; in what other situations were people at risk; and whether
this association is recognised by the medical profession. These issues have been
considered through review of a number of additional cases which have been
brought to the attention of the authors as a result of the initial publication.
In all cases, the relevant details were obtained by review of the hospital
medical records and patient interviews.
Methods
The clinical diagnosis of DVT or PE required
radiological confirmation by one of the following: positive compression Doppler
ultrasound; positive venography; high or intermediate probability V/Q scan;
positive helical CT with pulmonary angiography; or pulmonary
angiography.
ResultsThe clinical characteristics of the
five cases which met the inclusion criteria are shown in Table 1.
The presentations of the venous thromboembolic events were
striking in terms of the site of the venous thrombosis (proximal, including one
case of axillary and subclavian vein thrombosis), the life-threatening nature
(including bilateral lobar PE), and complications (including both a subsequent
extension and recurrence of a proximal lower limb DVT). In four cases, the
immobility related to prolonged periods of sitting at work—whereas in one
case, the subject sat for long periods at the computer at home, independent of
work.
In the weeks prior to the VTE event, the average length of
time per 24 hours spent seated at work and/or recreation ranged from 8 to 15
hours. The maximum number of hours in which the subjects spent seated at work or
recreation prior to the VTE ranged between 8 and 30 hours. The subjects reported
being seated between 3 to 6 hours at a time without getting up to stand or walk
around.
In four of the five cases, the role of prolonged seated
immobility was not recognised by the attending doctors, despite the possibility
being proposed by the patient in three of the cases.
DiscussionThis case series indicates that
individuals who sit for prolonged periods in relation to their work and/or
recreation may be at risk of developing a VTE. We previously termed this
disorder ‘eThrombosis’, due to the prolonged periods the initial
case spent seated in front of a computer.1
However, in view of the different occupations and recreations associated with
seated immobility, we have renamed this disorder the ‘seated immobility
thromboembolism’ (SIT) syndrome. The SIT syndrome would also encompass
other forms of seated immobility that are associated with VTE such as distance
air, train or car travel.2,3
The cases were characterised by the considerable length of
time the individuals sat and the extensive nature of the VTE events in young
individuals without other recognised risk factors. The other striking feature
was the lack of recognition by the attending doctors of seated immobility as the
most probable risk factor for the VTE event, in some cases despite the
possibility being raised with the doctor by the patient and the lack of
alternative risk factors.
The likelihood of a young adult without underlying risk
factors developing a proximal DVT or PE would be considered to be extremely
low,4,5 suggesting the importance of immobility
as a provoking factor in these subjects. Because this was not a prospective
study and subjects were predominantly identified by self-referral, it was not
possible to determine the relative frequency of seated immobility in cases of
VTE in young adults.
We acknowledge that the association between prolonged seated
immobility and VTE may be coincidental rather than causal, given the sedentary
nature of many people’s lives. However, in recognising the accepted role
of immobility as a risk factor for VTE, we propose the term ‘SIT
syndrome’ to encompass all forms of seated immobility that are associated
with VTE. This syndrome would include immobility associated with long distance
travel (air, train, road), prolonged computer use at work or in recreation, and
other situations associated with seating in cramped conditions such as the
theatre.1–3
Hopefully the acronym ‘SIT’ will facilitate the
recognition by doctors of the role of seated immobility as a risk factor for
VTE.
Author information:
Richard Beasley, Director, Medical Research Institute of
New Zealand, Wellington and Visiting Professor, University of Southampton,
UK; Patricia Heuser, Research Nurse, Medical Research Institute of New Zealand,
Wellington; Nigel Raymond, Consultant Physician, Wellington Hospital,
Wellington
Correspondence:
Professor Richard Beasley, Medical Research Institute of New Zealand, PO
Box 10055, Wellington. Fax: (04) 472 9199; email: richard.beasley@mrinz.ac.nz
References:
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