In her PhD thesis, Birgit Småbrekke has looked at the impact of atherosclerosis, ischemic stroke and prothrombotic genotypes on the risk of venous thromboembolism.

MAIN RESULTS:

1. The risk of venous thromboembolism is substantially increased after ischemic stroke.
2. There seems to be no association between atherosclerosis and risk of venous thromboembolism.
3. Prothrombotic genotypes do not influence the association between family history of myocardial infarction and higher venous thromboembolism risk.

THESIS DEFENCE:

Thesis: Shared risk factors for arterial cardiovascular diseases and venous thromboembolism
Candidate: Birgit Småbrekke
Time: June 28, 2019 at 13:15
Place: UiT The Arctic University of Norway, MH-Vest: Auditorium Cortex
Link to university website

SUMMARY:

(1) There is a 20-fold increased venous thromboembolism risk the first month after an ischemic stroke. The next couple of months the risk is still increased by 10-fold, but thereafter the risk increase is only 50 % compared to stroke-free subjects.

The study includes almost 30,000 participant from the three waves of the Tromsø Study conducted between 1994 and 2008 (Tromsø 4, 5 and 6). They were followed until the end of 2010. 1360 of the participants had an ischemic stroke during follow-up, and 722 had venous thromboembolism. All analyses were adjusted for several covariates, and the associations were independent of factors such as age, sex, BMI, smoking, diabetes, blood pressure, HDL cholesterol, physical activity and education.

(2) A single measurement of cardiovascular risk factors is sufficient to assess the risk of myocardial infarction and venous thromboembolism, according to Småbrekke’s second study. The researchers used data from 6,000 men and women who participated in Tromsø 4, as well as in Tromsø 5 and/or Tromsø 6. The risk estimates for myocardial infarction and venous trhomboembolism were more or less similar when using risk factors at Tromsø 4 in the analysis, compared to updating the risk factors over time.

(3) Neither carotid atherosclerosis nor plaque progression over time is linked to risk of venous thromboembolism. More than 10,000 participants who had their carotid arteries checked with ultrasound at at least one Tromsø Study between 1994 and 2008 were included in the analyses. 368 of them had incident venous thromboembolism during a median follow-up of ten years.

(2) High genetic risk of thrombosis does not seem to explain why a family history of myocardial infarction is linked to increased risk of venous thromboembolism. To have a first-degree relative with myocardial infarction was associated with 33 % higher risk of venous thromboembolism, and this risk increase was not altered by adjustment for five prothrombotic genotypes.

This study uses data from the Tromsø Study and the Nord-Trøndelag Health Study. 1500 cases of venous thromboembolism were compared to a subcohort of 13,000 controls without venous thromboembolism.

REFERENCES:

(1) Rinde, L. B., Småbrekke, B., Mathiesen, E. B., Løchen, M. L., Njølstad, I., Hald, E. M., Wilsgaard, T., Brækkan, S. K., & Hansen, J. B. (2016). Ischemic stroke and risk of venous thromboembolism in the general population: the Tromsø Study. Journal of the American Heart Association, 5(11), e004311.

(2) Småbrekke, B., Rinde, L. B., Hindberg, K., Hald, E. M., Vik, A., Wilsgaard, T., Løchen, M.-L., Njølstad, I., Mathiesen, E. B., Hansen, J.-B. & Brækkan, S. (2016). Atherosclerotic risk factors and risk of myocardial infarction and venous thromboembolism; Time-fixed versus time-varying analyses. The Tromsø Study. PloS one, 11(9), e0163242.

(3) Småbrekke, B., Rinde, L. B., Hald, E. M., Njølstad, I., Mathiesen, E. B., Johnsen, S. H., Hansen, J.-B., Brækkan, S. K., & Lijfering, W. M. (2017). Repeated measurements of carotid atherosclerosis and future risk of venous thromboembolism: the Tromsø Study. Journal of Thrombosis and Haemostasis, 15(12), 2344-2351.

(4) Småbrekke, B., Rinde, L. B., Evensen, L. H., Morelli, V. M., Hveem, K., Gabrielsen, M. E., Njølstad, I., Mathiesen, E. B., Rosendaal, F. R., Brækkan, S. K., & Hansen, J. B. (2019). Impact of prothrombotic genotypes on the association between family history of myocardial infarction and venous thromboembolism. Journal of Thrombosis and Haemostasis.