Seasonal variation in deep vein thrombosis: Fig 1

In many temperate countries coronary events and stroke, as well as related deaths, are more common in winter than in summer.1 Fatal pulmonary embolism has also been reported more often in winter.2 3 This might be linked to changes in coagulation factors4 and to peripheral vasoconstriction, leading to reduced blood flow in the legs.5 Alternatively, venous stasis due to vasodilatation is greatest in summer. These uncertainties prompted us to study the seasonal distribution of deep vein thrombosis of the legs by reviewing the month of presentation of all patients with this diagnosis referred to our vascular laboratory over six years. All files coded as “suspected” deep vein thrombosis (n=7303, mean (SD) age 63 (19), 58% women, 85% medical patients) or “confirmed” deep vein …