For all people – those with and without an inherited thrombophilia – a number of things can significantly affect the chances of having a venous thrombosis (blood clot). These include triggering events, lifestyle factors, age, and other health conditions.
When a person has a blood clot, it is the result of a variety of risk factors working together – not simply their genes. Many people are not aware of the lifestyle and other nongenetic risks that increase the chance they will develop a blood clot.
Triggering events include:- Immobility – such as hospitalization and prolonged bed rest
- Surgery – due to trauma, venous catheters, and prolonged bed rest
- Long distance travel – by airplane or automobile, lasting four or more hours
- Oral contraceptives (birth control pills)
- Pregnancy
- Hormone replacement therapy
- Sedentary lifestyle – not getting exercise
- Obesity – more than 30 pounds overweight (BMI chart)
- Smoking – heavy tobacco use
- Injury and infection
- Inflammatory disease
- Active cancer
For all people, as age increases, the risk of having a blood clot increases. Having a genetic risk for thrombophilia further increases the chance of having a blood clot.
| Risk of Having a DVT | Average | With Factor V Leiden |
Under age 40 | 1 in 10,000 | 1 in 1,750 |
| Age 40 – 50 | 1 in 1,250 | 1 in 1,100 |
| Age 50 – 60 | 1 in 1,100 | 1 in 476 |
| Age 60 - 70 | 1 in 833 | 1 in 250 |
| Age 70 – 80 | 1 in 625 | 1 in 120 |
While having inherited thrombophilia increases the risk of developing a dangerous blood clot, most people will never experience one.
It is also important to understand that risk factors are cumulative: the more risk factors you have, the higher the chance you will have a blood clot. Some risk factors, like age, cannot be changed, but many factors can be reduced by lifestyle changes or medical treatments.
