Risk factors for primary subclavian vein thrombosis in men and women

Introduction: Primary subclavian vein thrombosis (PSVT) is a rare (2/100.000/year) disorder, affecting predominantly young, healthy individuals. The disease can be idiopathic or effort-induced. The relative importance of risk factors for PSVT is not clarified, sex differences are mostly unknown. Studies show different incidence of idiopathic versus effort-induced PSVT. Aims: To investigate if risk factors differ between men and women with PSVT. The secondary aim was to examine differences regarding time from symptom to diagnosis and treatment between men and women. Material and Methods: 135 patients treated for PSVT in Stockholm county 2007-2017 was examined. Data on gender, age, weight, height, smoking, use of oral contraceptives, previous venous thrombotic events (VTE), family VTE, clotting disorders, were collected. Information on whether strenuous muscular activity preceded PSVT debut, and data on time variables where collected. Chi-2-test was used to evaluate differences in categorical data between men and women. Mann-Whitney U-test was used to evaluate time from symptom to first health care contact, diagnosis and treatment. One-way ANOVA was used to adjust for potential confounding variables for time data. Results: More men than women had effort-induced PSVT debut (p=0.006). Men had longer patient delay than women (p=0.064). The difference remained significant after adjustment for strenuous muscular activity. Conclusions: It was more common with effort-induced PSVT amongst men than women. Patient-delay was longer for men than women. Because of the study design, there was no control group, more research is needed to elucidate if causation is present.