The association between red cell distribution width and venous thromboembolism is not explained by myocardial infarction, stroke, or cancer

ESSENTIALS: Red cell distribution width (RDW) is associated with future risk of venous thromboembolism (VTE). Strong interrelations between RDW and other VTE‐related diseases may explain this relationship. Cause‐specific analyses were performed to asses risk estimates of VTE by RDW. The association between RDW and VTE was not explained by myocardial infarction, stroke, or cancer. BACKGROUND: Red cell distribution width (RDW) is a risk marker of venous thromboembolism (VTE), myocardial infarction (MI), stroke, and cancer. Due to interrelations between these diseases, the association between RDW and VTE may be explained by MI, stroke, or cancer. OBJECTIVE: To investigate whether the effect of RDW on VTE could be explained by intermediate development of MI, stroke, or cancer. METHODS: RDW was measured in 24 363 participants of the Tromsø Study in 1994‐1995. Incident VTE, MI, stroke, and cancer were registered until December 31, 2010. Conventional and cause‐specific Cox‐regression models were used to estimate hazard ratios (HR) for VTE with 95% confidence intervals (CI) across categories of RDW. RESULTS: There were 502 first VTEs during a median follow‐up of 16 years. In conventional Cox regression analysis, RDW in the highest quartile was associated with a 71% (HR 1.71, 95% CI 1.09‐2.67) and 27% (HR 1.27, 95% CI 0.88‐1.85) higher risk of VTE in men and women, respectively, compared to subjects in the lowest quartiles. The risk of VTE among subjects with RDW in the highest quartile was similar for men and women of postmenopausal age. In cause‐specific analysis, where each individual contributed with person‐time until the first occurring event only, the risk estimates were similar to those of the conventional Cox‐regression analysis. CONCLUSION: Our findings suggest that the association between RDW and future risk of VTE is not explained by intermediate development of MI, stroke, or cancer.