This Medical Monday series is about risk factors for venous thromboembolism, VTE (pulmonary embolism and DVT). The post ‘Are you on the red or blue team?‘ outlines the difference between arterial and venous clots.
We are going to cover
Strong risk factors; being in hospital, having surgery and immobility
Moderate risk factors; age (60+), a previous blood clot, family history of blood clots, thrombophilia, cancer, contraceptive pill and hormone replacement therapy
Other risk factors; obesity, pregnancy, smoking and alcohol
How high is the risk?
It is well recognised that venous thrombosis occurs more frequently as you get older. At the age of 25 yrs about 1 person in 10,000 will have a blood clot every year; by the age of 45 years the rate is approximately 1 in 3000, by 60 years 1 in 500 and by 85 years 1 in 120 people. There is an 80 fold increase from the age 20 to the age 80 years. Approximately 60% of all blood clots occur in people over the age of 70 years. The incidence of blood clots is similar in men and women. DVT is commoner than a pulmonary embolus in all age groups.
Why are blood clots more common as you get older?
This is a difficult question to answer as it is hard to just look at the effect of age alone on the risk of clots. For example as you get older you are more likely to be immobile, you are more likely to have cancer or other chronic medical conditions, and you are more likely to have surgery. So it is difficult to identify how much of the increased risk is due to these other factors and how much is due to just getting older? Using statistical methods it is possible to work out how much of the risk is due to age itself. This analysis shows that the reason you get more clots as you age is due largely (90%) to just getting older, the other factors only have a 10% influence on the risk.
What changes as you get older?
It is really not clear why just getting older makes you clot more easily. It is likely that many factors are involved, these included changes in the clotting proteins in the blood and changes to the lining of the blood vessels, which both make clots more likely. Also you lose muscle bulk and tone in your calf muscles as you get older, and as a result the calf muscles are less efficient at pumping blood out of your legs.
What does this mean for me?
One thing you can’t do is stop getting older! However recognising that age is a risk is important particularly in hospital and nursing home. Exercise can help as it changes the
concentrations of clotting proteins and encourages the release of a chemical called tPA which helps to break down blood clots. Exercise also improves muscle tone in the calf. It is also important to maintain a high protein intake as you get older to help maintain muscle bulk.