What risk factors contribute to blood clots?

What risk factors contribute to blood clots?

Risk factors are closely associated with overall causes of abnormal blood clots. Some of the most common include:

  • Artery associated blood clots (i.e. atherosclerosis): These may develop as a result of hypertension (high blood pressure), high cholesterol levels, diabetes, cancer, excess weight and obesity, smoking habits and a family history of blood clots, stroke or heart attack.
  • Blood clots occurring in the veins:  There are 3 main risk factors in this regard:

    1. Immobility
    2. Injury
    3. Genetic predisposition

    These may occur due to a sedentary lifestyle or an immobile state (lack of muscle movement or movement at all due to becoming bedridden or hospitalised following injury or due to a surgical procedure, such as joint replacements, orthopaedic and spinal cord damage, or paralysis, as well as during long-haul travel, such as long stretches of travel in cars, trains or aeroplanes which limit movement for more than 4 consecutive hours (4), or during pregnancy) or due to genetic errors in the blood’s clotting ability.

Other general risk factors include:

  • Age (blood circulation typically slows during senior years, post 65 years of age, which can increase risk for clots)
  • Excess weight and obesity
  • Chronic inflammatory diseases, such as rheumatoid arthritis or irritable bowel syndrome
  • Conditions which result in increased swelling of tissues can increase risk for clots – these include diverticulitis, acute pancreatic swelling, liver disease or appendicitis
  • Cirrhosis of the liver
  • Cancer
  • Oestrogen-based medications
  • Pregnancy (compression of veins in the lower extremities and pelvis due to the growing baby, results in slowing blood flow, as well as an increased tendency to clot in preparation for birth and following delivery, which increases the risk of developing a clot)
  • Genetic influences, such as a family history of blood clotting problems or disorders
  • One or more previous miscarriages



4. Centers for Disease Control and Prevention. December 2016. Blood Clots and Travel: What You Need to Know: https://www.cdc.gov/ncbddd/dvt/travel.html [Accessed 28.08.2018]

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