Incidence of Idiopathic Deep Venous Thrombosis and Secondary Thromboembolism among Ethnic Groups in California

BACKGROUND: Few studies have compared the incidence of deep venous thrombosis among ethnic groups. OBJECTIVE: To determine the incidence of deep venous thrombosis among ethnic groups. DESIGN: Analysis of the linked California Patient Discharge Data Set from 1991 to 1994. SETTING: California. PATIENTS: 17991 patients with idiopathic deep venous thrombosis (thrombosis without cancer or hospitalization within preceding 6 months) and 5573 patients with secondary thromboembolism (thromboembolism occurring within 3 months of seven different events). MEASUREMENTS: Ethnicity was determined by using race as documented in the data set. For idiopathic deep venous thrombosis, standardized age- and sex-adjusted incidences were calculated. For secondary thromboembolism, proportional hazards modeling was done. RESULTS: The annual incidence of idiopathic deep venous thrombosis per 1000000 persons older than 18 years of age was 230 for white persons, 293 for African Americans (rate ratio, 1.27 95% CI, 1.07 to 1.51), 139 for Hispanic persons (rate ratio, 0.60 CI, 0.54 to 0.67), and 60 for Asians and Pacific Islanders (rate ratio, 0.26 CI, 0.22 to 0.30). Compared with white persons, Asians and Pacific Islanders who developed secondary thromboembolism had a significantly lower relative risk (range, 0.22 to 0.61) for all seven conditions analyzed. CONCLUSIONS: Compared with white persons, Asians and Pacific Islanders have a very low incidence of idiopathic deep venous thrombosis and a very low relative risk for secondary venous thromboembolism.