Risk of pulmonary embolism and deep venous thrombosis in patients with asthma: a nationwide case-control study from Sweden.

Asthma is associated with an increased risk of pulmonary embolism (PE) but little is known about whether asthma is associated with an increased risk of deep venous thrombosis (DVT). The aim in this study was to determine the risk of the first event of PE, DVT or a combination of PE and DVT in patients with asthma.We conducted this nationwide case-control study using data from Swedish nationwide registries. We included 114 366 Swedish-born patients with a first hospital diagnosis of PE, 76 494 patients with DVT and 6854 patients with both PE and DVT in Sweden between 1981 and 2010. We also included five age-, sex- and education-matched population controls. All previous hospital diagnoses of asthma were identified. Conditional logistic regression was used to compute odds ratios with adjustment for potential confounders.Asthma was associated with an adjusted odds ratio for PE of 1.43 (95% CI 1.37-1.50), for DVT of 1.56 (95% CI 1.47-1.65) and for combined PE and DVT of 1.60 (95% CI 1.32-1.93). Asthma was associated with an increased risk of PE, DVT and combined PE and DVT.Thus, the inflammation conferred by asthma seems to have systemic (and not just local) prothrombotic effects with increased risk of both DVT and PE.