Short and tall body height and the effect on venous blood flow

In the Netherlands there are around 800.000 people taller than average (> 1.90
m for men, and > 1.80 m for women), and approximately 2500 people smaller than
average (< 1.51 m for men and < 1.45 m for women). The number of tall people is
expected to increase. A recent study showed that people with a short stature
have a reduction in health related quality of life. In people with a tall
stature quality of life data is lacking.

The extremes of body height come with physical limitations in public transport
and public space. Examples are little leg space or unadjustable seat height.
This does not only lead to physical inconvenience, but also to physical
complaints: a Norwegian cohort study found a 2-fold increased risk of venous
thrombosis in men taller than 1.81 m.
In two previous studies we showed that in people with a body height above 1.85
m, the risk of venous thrombosis was 1.5 to 4.5 times increased after a long
haul flight, as compared to people of average height. For people smaller than
1.60 m this risk was about 3-fold increased. Besides, unpublished results from
the MEGA case-control study showed that there is an increased risk of venous
thrombosis for extremes of body height in people that have seated immobility at
work.

Venous thrombosis is a disease that comes with morbidity and even mortality
(e.g. death of acute pulmonary embolism). When seats are not height adjustable,
it is possible that in people with short stature the popliteal veins become
compressed and stasis of venous blood occurs. In people with a tall stature,
stasis occurs when due to little leg space the legs are folded and therefore
popliteal veins become compressed. A previous study showed that people that are
seated in a way that their feet can not touch the floor, had a decreased venous
blood flow velocity, as compared to sitting with feet touching the ground.
As a marker of venous thrombosis risk, we used stasis (or remaining flow) in
the popliteal veins. The velocity of the venous blood can be measured using
ultrasonography imaging. Our hypothesis was that in people with a taller or
shorter stature than average, a decreased mean flow and peak flow in the
popliteal vein would be found.
The results of this study, will tell us what optimal sitting positions are, and
which positions should be avoided. Physical complaints should not occur, and
the risk of venous thrombosis should not be increased.

To investigate the effect of different sitting positions that are experienced
in public transport by people of taller or shorter height than average on
venous blood flow.

observational study

In this study, all participants are asked to come to the Leiden University
Medical Center for a single study visit including a questionnaire and an
ultrasonography examination.
Ultrasonography is a non-invasive technique without radiation. The study poses
no risks for the participants.