Red cell distribution width and all‐cause mortality in patients with atrial fibrillation: A cohort study

Background Increased red cell distribution width (RDW), a measure of red cell size variability, has been associated with increased mortality in multiple cardiovascular diseases. However, whether RDW is associated with increased mortality in patients with atrial fibrillation remains unknown. Methods Using the computerized database of the largest health maintenance organization in Israel, we identified a cohort of adults with atrial fibrillation diagnosed before January 1, 2012. Cardiovascular risk factors and comorbidities were ascertained using an electronic medical record–based algorithm. Mortality was established using the National Death Index through December 31, 2013. Results Of 69,412 patients, 12,104 (17.4%) participants died during follow‐up. The crude, two‐year cumulative all‐cause mortality rate increased across RDW quartiles; 9.8%, 13.6%, 18.8%, and 28.5%, respectively. After adjustment for age, sex, anemia, cardiovascular risk factors, comorbidities, and medication use, compared to the lowest RDW quartile, the hazard ratio (HR) for mortality was 1.20 (95% CI, 1.13–1.27) in the second quartile, 1.44 (1.36–1.53) in the third quartile, and 1.90 (1.79–2.00) in the highest RDW quartile. The results were similar after further adjustment for smoking, socioeconomic status, renal function, low and high density lipoprotein cholesterol levels, with HR=1.82 (1.71–1.93) in the highest RDW quartile compared to the lowest quartile. Changes in RDW over time were strongly associated with mortality; increased RDW was associated with higher risk of mortality and decline in RDW was associated with decreased mortality. Conclusions RDW and changes in RDW are independently associated with the risk of all‐cause mortality in patients with atrial fibrillation.