JAK2 and Venous thrombosis: Treatment for MPNs at baseline was less often administered for patients with headaches than for patients without headaches (low-dose aspirin: 24.3 vs. 62.0%, P < 0.001; cytoreductive therapy: 27.0 vs. 57.0%, P = 0.002), because treatments for MPNs are usually initiated in patients with a higher risk of thromboembolic events (age > 60 years, history of thrombosis and/or vascular risk factors, and presence of the JAK2 V617F mutation).