Physical inactivity and idiopathic pulmonary embolism in women: prospective study
BMJ 2011; 343 doi: https://doi.org/10.1136/bmj.d3867 (Published 04 July 2011) Cite this as: BMJ 2011;343:d3867All rapid responses
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I read with interest this article and would like to give some
comments.
Firstly, in this study, important risk factors such as surgery and
major trauma within one month of the diagnosis of pulmonary embolism and
active malignancy were excluded. However, the relative risk of
postoperative venous thromboembolism (VTE) following inpatient surgery
persists beyond 1 month and is still high up to 12 months (relative risk
19.6 at 7-12 weeks, 9.4 at 4-6 months, 6.1 at 7-9 months and 3.7 at 10-12
months) according to a prospective cohort study in middle aged women [1].
Therefore, some of the so-called idiopathic pulmonary embolism (PE) cases
which developed 1 month after surgery in this study could have been
related to postoperative PE.
Secondly, hereditary and acquired thrombophilic disorders are not
rare. Population studies revealed that 4.4-7.0% of the Caucasian
population have heterozygous factor V Leiden mutation (0.01% have
homozygous mutation), while 2% have prothrombin gene mutation [2-3].
Although the exact prevalence of antiphospholipid syndrome is not known,
antiphospholipid antibodies are detectable in 1.0-5.0 % of the young
population and their prevalence increases with age (in one study, up to
51.6% positivity in the elderly population) and therefore, the possibility
of antiphospholipid syndrome is not low [4,5].
Considering those facts, if the authors retrospectively and
aggressively look at their data now, I am certain their statistical data
are likely to be different (i.e. how many of their so-called idiopathic PE
are actually idiopathic?). As a practicing consultant haematologist, I
consider idiopathic VTE as a disease of rigorous exclusion. All known
hereditary and acquired thrombophilic conditions should be excluded before
establishing the diagnosis of idiopathic VTE. It is high time that the
world's "Thrombosis and Haemostasis" community should get together to
define "idiopathic thrombosis" so that future research studies on this
topic will be standardized.
References:
(1)Sweetland S, Green J, Liu B et al. Duration and magnitude of the
postoperative risk of venous thromboembolism in middle aged women:
prospective cohort study. BMJ 2009;339:b4583
(2)Rees DC, Cox M, Clegg JB. World distribution of factor V Leiden.
Lancet 1995;346: 1133-4
(3)Rosendaal FR, Doggen CJ, Zvelin A et al. Geographic distribution
of the 20210 G to A prothrombin variant. Thromb Haemost 1998;79:706-8
(4)Petri M. Epidemiology of the antiphospholipid antibody syndrome. J
Autoimmun 2000;15:145-151
(5) Manoussakis MN, Trioufas AG, Silis MP et al. High prevalence of
anticardiolipin and other antibodies in a healthy elderly population. Clin
Exp Immunol 1987;69:557-565
Competing interests: No competing interests
Risk of pulmonary embolism related to inactivity and to air travel
Results of the study from Kabrhel at al. are disturbing.1 There are
great similarities with the risk of pulmonary embolism related to air
travel. The absolute risk of pulmonary embolism remains low.1, 2 Physical
inactivity is the major risk factor in both situations. Minimal physical
activity contributes to reduce the risk.3 Women could be at higher risk.4
The role of other potential risk factors is uncertain. Finally, the major
risk factor appears to be the time of the exposure. In both cases, the
duration of inactivity remains the crucial point. Only time scale changes.
In the first case, the risk is counted in years.1 In the case of air
travel, it is measured in hours.2 In the study from Kabrhel at al., the
number of EP reported during the follow-up period is low for an amount of
sitting between 2 to 4. It increases linearly after 4. The relation
between pulmonary embolism and air travel is similar. Risk is low for
flight under 6 to 7 hours (i.e. for distances under 5.000 km). It
increases linearly for travels of more than 6 to 7 hours. In both cases,
the curve suggests that there is a threshold-time for an increased risk of
pulmonary embolism, whether it is during air travel or not.
Lapostolle F, Alheritiere A, Grave M, Adnet F
SAMU 93, Hopital Avicenne, Bobigny, France
References
1. Kabrhel C, Varraso R, Goldhaber SZ, Rimm E, Camargo CA Jr.
Physical inactivity and idiopathic pulmonary embolism in women:
prospective study. BMJ 2011 Jul 4;343:d3867. doi: 10.1136/bmj.d386
2. Lapostolle F, Surget V, Borron SW, Desmaizi?res M, Sordelet D, Lapandry
C, Cupa M, Adnet F. Severe pulmonary embolism associated with air travel.
New England J Med 2001;345:779-83
3. Schobersberger W, Toff WD, Eklof B, et al. Traveller's thrombosis:
international consensus statement. Vasa 2008;37:311-7
4. Lapostolle F, Le Toumelin P, Chassery C, Galinski M, Ameur L, Jabre P,
Lapandry C, Adnet F. Gender as a risk factor for pulmonary embolism after
air travel. Thrombosis Haemostasis 2009;102:1165-68
Competing interests: No competing interests