Risk factors for venous thromboembolism in Japan: a hospital-based case-control study.

Background: Previous studies suggest that Asians may be less likely to develop venous thromboembolism (VTE) than Caucasians. While inherited thrombophilias occur infrequently among Asians, the distribution of other VTE risk factors in these populations remains unclear.

Objective: To identify VTE risk factors in a Japanese population.

Patients And Methods: We evaluated 131,060 patients admitted to Okinawa Chubu Hospital in Japan (January 1987-December 1999). Patients with VTE were identified through discharge diagnoses using the hospital database. Medical records were reviewed for information on demographics, potential VTE risk factors, and diagnostic modalities. Controls were randomly selected from the same database, matched 1:1 to cases on age, sex, year of hospital admission, and nearest medical record number We used conditional logistic regression to examine potential VTE risk factors.

Results: We identified 141 cases of newly diagnosed VTE (128 with deep vein thrombosis, 41 with pulmonary embolism). In multivariable analyses adjusting for all measured potential risk factors, statistically significant VTE risk factors included lower extremity paralysis [odds ratio (OR), 3.07; 95% CI, 1.01-9.33], immobilization >7 days (OR, 4.96; 95% CI, 2.26-10.9), diagnosis of an acquired hypercoagulable state (OR, 19.1; 95% CI, 1.75-209.2), body mass index > or = 25.0 kg/nm2 (OR, 2.35; 95% CI, 1.13-4.89), and prior VTE (OR, 22.37; 95% CI, 2.35-213.4).

Conclusion: The VTE risk factors identified in this Japanese population are similar to those previously described among Caucasians. Further study is needed to define how the distribution of VTE risk factors in Asian populations may influence appropriate preventive strategies.