Don't Just Sit There, Do Something! Part 2

We've talked ad nauseum about how exercise decreases one's risk for cognitive dysfunction, diabetes, heart disease, (all-cause) mortality, and obesity.  For better or worse, in a new study published last week, we can now add pulmonary embolism to the list of conditions associated with prolonged sitting.

We've known for some time that major (orthopedic) surgeries and prolonged immobilization can increase one's risk for deep venous thrombosis (DVT).  So can cancer, pregnancy, some more rare conditions, eg anti-phospholipid syndrome, and some medications, eg non-bio-identical hormones.  Besides chronic thrombophlebitis, the biggest concern is for pulmonary embolism (PE), whereby the clot moves from the leg into the lungs, leading to abrupt (and often fatal) vascular collapse.  That's why pre- & post-operative prevention is paramount.  Professional tennis player, Serena Williams, had good luck on her side recently as she survived her bout of PE.

But the question has always been how long is too long with regards to immobilization.  For instance, there is some evidence that transoceanic flights, whereby one is stuck in tight cramped quarters for hours on end in economy class, can slightly increase one's risk for DVT.  In an 18 year analysis of 69,950 women in the Nurses' Health Study, the authors noted that women who sat for more than 41 hours a week outside of work had twice the risk of PE as those who sat for less than 10 hours a week outside of work.

However, the analysis wasn't 100% foolproof as the inverse (converse?) did not prove true:  there was no (inverse) association between physical activity and PE.  So how can physical inactivity be problematic while physical activity be ineffective?  Remember once more that this study was observational in nature and therefore useful only in developing hypotheses & theories.  Furthermore, physical (in)activity is not a one-time factor, akin to radiation exposure, but rather subject to the vagaries of life.  On the other hand, physical (in)activity was assessed just twice during the almost 2 decade duration of this analysis.  The editorialists point out many other reasons to explain the results.  In the end, while not absolutely supportive & concrete in proof, I look at this study as another reason to stop sitting and get moving.