Incidence of Recurrent Venous Thromboembolism in a Population-Based Cohort.

The incidence of recurrent venous thromboembolism (VTE) changes over time from the first VTE event and depends on the presence of risk factors. In this study, we aimed to determine the yearly incidence of VTE recurrence during five years of follow-up after a first-ever VTE event. For this cohort study, we identified persons who experienced a validated first-ever VTE between 2006-2014 in northern Sweden. These patients' medical records were reviewed to identify recurrent VTE events during five years of follow-up. The yearly incidence rates (IRs) of recurrent VTE per 100 person-years were calculated and stratified into three groups defined by characteristics at the first-ever VTE event: no risk factors, cancer, or other risk factors. A total of 1413 persons experienced a first-ever VTE during the study period, of whom 213 experienced a recurrent VTE. Among persons without risk factors, the IR was 4.2 during the first year of follow-up, and 4.1 during the fifth year. Among persons with cancer, the IR was 9.5 during the first year, and 5.4 during the fifth year. Among persons with other risk factors, the corresponding IRs were 6.1 and 2.3. In conclusion, after a first-ever VTE event, persons with cancer had the highest recurrence rate during the first years of follow-up. Among persons with cancer who were alive after five years, the incidence of recurrent VTE during the fifth year was similar to that in participants without risk factors.