Higher red cell distribution width and poorer hospitalization-related outcomes in elderly patients.

BACKGROUND: Red cell distribution width (RDW), an index for variation of red blood cell (RBC) size, has been proposed as a potential marker for poorer outcomes in several aging-related diseases and conditions. We tested whether greater variability of RBC size, presented as a higher RDW value, predicts poor prognoses among hospitalized patients over 60 years old. METHODS: We retrospectively collected data from older hospitalized patients aged ≥60 years between January 2013 to December 2017 at Sutter Health, a large integrated health system in Northern California. The RDW was measured during hospital admission and categorized with 1% intervals (≤13.9, 14.0-14.9, 15.0-15.9, 16.0-16.9, 17.0-17.9 and ≥18.0%). The primary outcome was the rate of in-hospital mortality and secondary outcomes included 30-day re-admission rate and length of hospital stay (in days). RESULTS: A total of 167,292 admissions from 94,617 patients were included. The overall in-hospital mortality rate was 6.3%. As the RDW value increased, the rate of in-hospital mortality gradually increased from 2.7% for the lowest RDW category to 12.2% in the highest category (p-trend <0.001). The overall 30-day re-admission rate after discharge was 12.5% and the rate of 30-day re-admission also increased with increasing RDW categories (7.4% in the lowest group vs. 15.8% in the highest group, p-trend <0.001). Patients with the highest RDW values at admission stayed 1.5-2.0 times longer in the hospital than patients with lower RDW values who were admitted for the same causes. CONCLUSIONS: Greater variability of RBC size is significantly associated with worse prognosis in hospitalized elderly patients, indicating higher mortality, greater risk of early re-admission, and longer hospital stay days. Risk stratification strategies for hospitalized elderly should include RDW value.