Beth Waldron, Program Director of Clot Connect, writes…
The claim: “Eating lunch at your desk could increase your risk of DVT”—was the dramatic headline from UK’s Marie Claire magazine which caught my attention. (1) The online story went on to say that “Almost 75 per cent of office staff aged 21-30 who work 10-hour days don’t get up to take a break. This could double chances of a fatal blood clot.” The story was light on citing scientific evidence to back up this claim, so, as someone interested in DVT education (and admittedly, who eats at her desk routinely), I decided to investigate if this assertion is true: Does eating lunch at your desk increase blood clot risk?
The answer: Yes. The act of eating lunch at your desk, in and of itself, does not increase blood clot risk; but the immobility associated with prolonged sitting at your desk, does.
The research facts: The association between immobility and venous thromboembolism (VTE) is well-accepted in the literature. The term VTE includes deep vein thrombosis (DVT; blood clots in the legs) and pulmonary embolism (PE; blood clots in the lungs) . Immobility associated with hospitalization, prolonged bedrest, cramped airline and long-distance travel increases VTE risk and has received notable attention from both the health care community and the media. The association between prolonged sitting at work and VTE risk has received much less acknowledgement, even thought the association between sitting and VTE was first reported in the New England Journal of Medicine in 1954.(2) The term “eThrombosis” was coined in a case report from 2003, in which occurrence of a DVT in a patient who sat prolonged periods at a computer was described.(3)
A 2010 study from New Zealand found that “prolonged work- and computer-related seated immobility was associated with a 2.8 fold increased risk of VTE.”(4) Additionally, the risk of VTE was found to increase by 10% for each additional hour seated.(4) The risk of VTE was significantly increased in persons who had their own desk at work and in those who usually ate lunch at their desk.(4)
A 2011 US study reporting results from the large and well-respected Nurses Health Study found that “the risk of pulmonary embolism was more than twofold in women who spent the most time sitting compared with those who spent the least time sitting”.(5)
Seated immobility, no matter the reason why one is seated—if from long-travel, desk work, computer use, video games or even watching television— slows blood flow in the legs, which may contribute to clot formation. After just 90 minutes of sitting, the flow of blood to the popliteal vein (behind the knee) is reduced by 40%.(6)
The practical implications:
1. Cause of VTE affects treatment decisions
Recognition that prolonged sitting at work can contribute to VTE has serious implications. Twenty-five percent of VTE cases are considered idiopathic, ie no clear risk factor precipitating the VTE event can be identified.(7) Given the sedentary nature of the modern office environment, could it be that occupational risks are a greater provoking factor in some VTE cases than is commonly realized? It is a question warranting further study and discussion since an accurate assessment of whether a VTE was provoked or idiopathic affects decisions related to the length of anticoagulant treatment.
2. Everyone should know the risk of VTE, including healthy office workers who do not perceive themselves at risk from simply sitting at their desk.
VTE is a common medical condition and preventing blood clots associated with immobility and venous stasis is simple: movement. In recent years, greater public emphasis has been placed on the negative health consequences (obesity, diabetes, heart disease, etc) of a sedentary lifestyle, but rarely is VTE mentioned in an appeal to increase physical activity. Greater public awareness is needed that immobility—in all its various forms—is a risk factor for potentially life-threatening blood clots.
3. Occupational strategies to reduce risk and prevent VTE
If you spend your work days sitting at a desk, there are things you can do to reduce your blood clot risk:
Get up every hour and stretch your legs. Take a short walk around the office. Get outside at lunch for a longer walk.
If you can’t get away from your desk, exercise your legs while you’re sitting. The CDC recommends(8):
- Raising and lowering your heels while keeping your toes on the floor.
- Raising and lowering your toes while keeping your heels on the floor.
- Tightening and releasing your leg muscles
- “Eating lunch at your desk could increase your risk of DVT” http://www.marieclaire.co.uk/news/health/538820/eating-lunch-at-your-desk-could-increase-your-risk-of-dvt.html
- “Thrombosis of the Deep Leg Veins Due to Prolonged Sitting” John Homans N Engl J Med 1954 Jan 250:148-149
- “eThrombosis: the 21st century variant of venous thromboembolism associated with immobility.” Beasley R, Raymond N, Hill S, Nowitz M, Hughes R. Eur Respir J. 2003 Feb;21(2):374-6.
- “Prolonged work- and computer-related seated immobility and risk of venous thromboembolism” Healy B, Levin E, Perrin K, Weatherall M, Beasley R. J R Soc Med. 2010 Nov;103(11):447-54.
- “Physical inactivity and idiopathic pulmonary embolism in women: prospective study” Kabrhel C, Varraso R, Goldhaber SZ, Rimm E, Camargo CA Jr. BMJ. 2011 Jul 4;343.
- “Effect of leg exercises on popliteal venous blood flow during prolonged immobility of seated subjects: implications for prevention of travel-related deep vein thrombosis.” Hitos K, Cannon M, Cannon S, Garth S, Fletcher JP. J Thromb Haemost. 2007 Sep;5(9):1890-5.
- “Relative impact of risk factors for deep vein thrombosis and pulmonary embolism: a population-based study” Heit JA, O’Fallon WM, Petterson TM, Lohse CM, Silverstein MD, Mohr DN, Melton LJ 3rd Arch Intern Med. 2002 Jun 10;162(11):1245-8.
- CDC DVT prevention recommendations: http://www.cdc.gov/ncbddd/dvt/documents/DVT-Tip-sheet.pdf