Autumn season birth is associated with a lower frequency of diagnosis of unprovoked deep vein thrombosis in the emergency department

A significant association was described between lifetime frequency of several human diseases, including cardiovascular disorders, and birth season. We performed a retrospective study to establish whether an association exists between birth season and frequency of venous thromboembolism diagnosed in the emergency department. The study population consisted of all consecutive patients diagnosed with venous thromboembolism at the emergency department of the University Hospital of Parma (Italy) during the year 2014. A total number of 400 patients (217 women and 183 men; mean age 70 ± 18 years) received a final diagnosis of venous thromboembolism throughout the study period. The lowest frequency of diagnoses was observed in patients born in autumn, whereas a higher frequency was observed in those born in spring or summer. When compared with the frequency of births in the same geographical area, patients born in spring and summer exhibited a 30 and 25% higher risk of venous thromboembolism compared with those having autumn birth. A similar trend was observed in patients with unprovoked thrombosis, but not in those with provoked thrombosis. A subanalysis of patients with unprovoked deep vein thrombosis revealed that both spring birth (relative risk 1.49, 95% confidence interval 1.04-2.14) and summer birth (relative risk 1.46, 95% confidence interval 1.01-2.09) were significant risk factors for this condition compared with autumn birth. Although further studies are needed to confirm these original findings, it seems reasonable to hypothesize that birth season may influence the lifetime risk of venous thromboembolism, especially of unprovoked deep vein thrombosis.