Background: Several studies suggest a lower risk of venous thromboembolism (VTE) in Asians compared to other racial groups, and genetic mechanisms have been suspected. Despite their biological and cultural diversity, data have been sparse comparing risk of VTE among specific Asian ethnicities. Our previous report from 2000 on hospitalizations for VTEs in Asian Americans had included 337 subjects (all races) and numbers were insufficient to study specific Asian groups. We present here data from a new study with 4,674 VTE subjects.
Hypothesis: Similar low VTE risk is present in multiple Asian ethnic groups.
Methods: We studied composite VTE risk in 61,459 members of a comprehensive health plan, who had supplied self-classified ethnicity data on prior health examinations between 1978 and 1985 and had remained plan members in 1996, when outpatient diagnoses were added to computerized files. The subjects were 58% (n = 35,573) female and 42% (n= 25,886) male. From 1996 through 2015, at least one diagnosis of VTE was made during an outpatient visit or hospitalization for 4,675 persons. With Whites as the referent group, we performed logistic regressions controlled for age, sex, education, BMI, and smoking, yielding hazard ratios (HR) and 95% confidence intervals (CI).
Results: The table shows HRs (CI) versus Whites (n=32,557) with 2,576 VTE.
These lower HRs for VTE in Asians were generally similar in men and women. In the Asian stratum, a model with Chinese as referent showed an increased HR = 1.87 (1.09-3-21; p=0.02) for South Asians. Among covariates sex, education, and smoking were unrelated to VTE risk and BMI was positively associated; these results were similar in Whites, Blacks, and Asians.
Conclusions: In conclusion, Chinese, Japanese, Filipinos and Other Asian Americans but not South Asians had substantially lower VTE risk compared to Whites. These data indirectly support a genetic explanation.