Introduction: Venous thromboembolism incidence rates are 30%-100% higher in US blacks than whites. We examined the degree to which differences in the frequencies of socioeconomic, lifestyle, medical risk factors, and genetic variants explain the excess venous thromboembolism risk in blacks and whether some risk factors are more strongly associated with venous thromboembolism in blacks compared with whites. Methods: We measured venous thromboembolism risk factors in black and white participants of the Atherosclerosis Risk in Communities study in 1987-1989 and followed them prospectively through 2015 for venous thromboembolism incidence. Results: Over a mean of 22 years, we identified 332 venous thromboembolisms in blacks and 578 in whites, yielding 65% higher crude incidence rates per 1000 person-years in blacks. The age and sex-adjusted hazard ratio (95% confidence interval) of venous thromboembolism for blacks compared with whites was 2.04 (1.76, 2.37) for follow-up > 10 years and was attenuated to 1.14 (0.89, 1.46) when adjusted for baseline confounders or mediators of the race association, which tended to be more common in blacks. For example, adjustment for just baseline weight, family income, and concentration of plasma factor VIII reduced the regression coefficient for race by 75%. There were no significant (P < 0.05) 2-way multiplicative interactions of race with any risk factor, except with a 5-single nucleotide polymorphism (5-SNP) genetic risk score (a weaker venous thromboembolism risk factor in blacks) and with hospitalization for heart failure (a stronger venous thromboembolism risk factor in blacks). Conclusion: The higher incidence rate of venous thromboembolism in blacks than whites was mostly explained by blacks having higher frequencies of venous thromboembolism risk factors.
Bibliographical noteFunding Information:
We thank the ARIC participants and staff for their important contributions to ARIC research. Funding: The National Heart, Lung, and Blood Institute provided support for venous thromboembolism identification via R01 HL059367 and for the Atherosclerosis Risk in Communities Study via contracts HHSN268201700001I, HHSN268201700002I, HHSN268201700003I, HHSN268201700004I, and HHSN268201700005I. The manuscript contents are solely the responsibility of the authors and do not necessarily represent the official view of the National Institutes of Health.
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