The aim of this thesis was to identify new risk factors for first and recurrent venous thrombosis of both the upper and lower extremity, and assess the incidence of recurrence and mortality after a... Show moreThe aim of this thesis was to identify new risk factors for first and recurrent venous thrombosis of both the upper and lower extremity, and assess the incidence of recurrence and mortality after a first venous thrombosis. An overview was provided of the current literature on risk factors and treatment for a first venous thrombosis of the upper extremity (chapter 2). We investigated the association between levels of coagulation factors, blood group and a first venous thrombosis of the upper extremity (chapter 3), and studied risk factors for a recurrent event in patients with a first venous thrombosis of the upper extremity (chapter 4). Furthermore, we studied the association between venous thrombosis and long-term mortality (chapter 5). In this study we found that patients with thrombosis died more of chronic obstructive pulmonary disease (COPD) than expected from population figures. COPD was found to be a risk factor for a first venous thrombosis in chapter 6. We studied the incidence of recurrent venous thrombosis, as well as sex, age and an idiopathic first venous thrombosis as risk factors for recurrence (chapter 7). Body height was studied as a risk factor for both first and recurrent venous thrombosis in combination with mobility (chapter 8). Show less
Oral contraceptive use is associated with venous thrombosis. However, the mechanism behind this remains unclear. The aim of this thesis was to evaluate genetic variation in the first-pass... Show moreOral contraceptive use is associated with venous thrombosis. However, the mechanism behind this remains unclear. The aim of this thesis was to evaluate genetic variation in the first-pass metabolism of contraceptives, to identify the clinical implications of hormonal contraceptive use after a thrombotic event and to provide an overview of the risk of venous thrombosis per combined oral contraceptive. We found that the UGT2B7 gene in the first-pass metabolism may at least in part explain the risk of venous thrombosis in oral contraceptive users. Furthermore, 20% of women continued or switched to a different contraceptive after a thrombotic event. Contraceptive use after an event was associated with a threefold increased risk of recurrent venous thrombosis, which depended on the ethinylestradiol dose, type of progestagen and whether the contraceptive was triphasic or not. All ten combined oral contraceptives commonly used and included in the analysis increased the risk of a first venous thrombosis. The highest risk of venous thrombosis was found among users of drospirenone with 30 _g ethinylestradiol, cyproterone acetate with 35 _g ethinylestradiol and levonorgestrel with 50 _g ethinylestradiol. Users of levonorgestrel with 20 _g ethinylestradiol had the lowest risk of venous thrombosis among combined oral contraceptive users. Show less
