Abstract
Red cell distribution width (RDW), routinely assessed as a component of a complete blood count (CBC), quantifies the variation in the size of red blood cells. It increases with age, and increased RDW predicts many aging-related diseases and mortality. However, whether it also predicts hip fracture is unknown. We prospectively evaluated the association between RDW and hip fracture using data from the Osteoporotic Fracture in Men (MrOS) study. RDW was measured in 3635 men (aged 71 to 99 years) along with bone mineral density (BMD) in MrOS. RDW ranged from 11.3% to 32.9% (median 14.0%; interquartile range 13.5% to 14.8%) and was categorized into four groups (≤13.0%, 13.1% to 14.0%, 14.1% to 15.0%, ≥15.1%). Study participants with a hemoglobin level <13.0 g/dL were classified as having anemia. During an average 8.1 years, 164 men suffered hip fractures. The risks of hip fractures increased with increase of RDW category. Furthermore, there was a significant interaction between anemia and RDW: An association between RDW and hip fractures was only observed in participants without anemia. In those without anemia, the relative hazard of hip fractures increased with increases in RDW category: Men in the highest RDW category had a 2.8 times higher risk of hip fractures than men in the lowest group (95% confidence interval 1.1 to 7.1). The risks of all-clinical fractures were also increased along with higher RDW values. Additionally, RDW was significantly associated with the risk of having a fall but not with femoral neck or total hip BMD. In conclusion, RDW and anemia defined by hemoglobin are widely available routine laboratory measurements that together could indicate increased risk of hip fracture, reflecting the neuromuscular effects of aging rather than lower hip BMD. © 2020 American Society for Bone and Mineral Research.