Contemporary Estimates of the Incidence of Venous Thromboembolism: A Population-Based Cohort Study

Venous thromboembolism (VTE) is a growing public health problem due largely to the aging population and the increasing prevalence of known risk factors such as surgery and cancer-related treatments. As a result, the true burden of VTE is not fully known and more contemporary estimates of incidence are needed.

We estimated the incidence of a first VTE event in a general population.

This retrospective, observational study used the linked administrative healthcare databases of the province of Québec, Canada, including the province-wide hospitalization database (MED-ÉCHO) and the healthcare services database of RAMQ which oversees all physician reimbursement claims for services provided to Québec residents. From a source population of all RAMQ beneficiaries with a physician visit or a hospitalization associated with an ICD-9-CM or ICD-10-CA diagnosis code for deep vein thrombosis (DVT) or pulmonary embolism (PE) recorded between January 1, 2000 and December 31, 2009 and without a DVT or PE code prior to January 1, 2000, we identified a cohort of Québec residents with definite incident VTE and a cohort with definite or probable incident VTE. We used a priori determined diagnostic algorithms using RAMQ and MED-ÉCHO data to identify definite and probable cases of VTE. Subjects were followed forward in time from first-time VTE occurrence until the earliest of either death or end of study period (December 31, 2009). Incidence rates of first VTE, DVT alone, and PE with or without DVT were calculated by dividing the number of new cases by the total person-years at risk in the population of Québec residents eligible for RAMQ between 2000 and 2009. Age-specific incidence rates and associated 95% confidence intervals (CI) were calculated using achieved age during follow-up, and as a result patients contributed person-time in different age categories while aging during follow-up. Crude and age-adjusted incidence rate ratios (IRR) were reported comparing rates among women and men.

From the 245 452 Québec residents between 2000 and 2009 with at least 1 VTE diagnosis in RAMQ or MED-ÉCHO (source population), we identified 67 410 cases with definite VTE and 35 123 cases with probable VTE. The incidence rate of definite VTE was 0.91 per 1000 person-years (95% CI: 0.90–0.91). For DVT alone, the incidence was 0.53 per 1000 person-years (95% CI: 0.52–0.52) and for PE with or without DVT it was 0.38 per 1000 person-years (95% CI: 0.38–0.38). The incidence rates increased with age, and rates in patients 70 years of age and older were more than 4 times higher than rates in patients who were 40–69 years of age (Table 1). The VTE incidence rate was 0.99 per 1000 person-years (95% CI: 0.98–1.00) in women as compared to 0.82 per 1000 person-years (95% CI: 0.81–0.83) in men. The IRR was 1.19 (95% CI: 1.17–1.22) but this sex difference was no longer seen when adjusted for age (IRR 0.98; 95% CI: 0.96–1.01). The corresponding VTE, DVT alone, and PE incidence rates per 1000 person-years for definite or probable VTE were 1.24 (95% CI: 1.23–1.24), 0.79 (95% CI: 0.78–0.79), and 0.45 (95% CI: 0.45–0.46), respectively.

Our study provides real-world contemporary estimates of VTE incidence. The risk in the general population is about 0.9 to 1.2 per 1000 person-years and is highest in the elderly. These data may help inform public healthcare planning and future research.

No relevant conflicts of interest to declare.