Hip fracture risk predicted by red blood cell width

American Society for Bone and Mineral Research (ASBMR) 2019 Annual Meeting

Hip fracture risk can be predicted by a biomarker commonly included in a complete blood count (CBC). Medscape Medical News reports on a study presented at the recent American Society for Bone and Mineral Research (ASBMR) 2019 Annual Meeting offering evidence that RDW (red blood cell distribution width) compares in accuracy to the best available methods for predicting hip fracture.

Almost three times the risk for hip fracture in men

The authors of the study evaluated 3635 older men for hip fractures, femoral neck bone mineral density (BMD), and RDW and found that those in the highest third of RDW (> 15.7%) compared to the lowest (< 13.0%) had an almost threefold higher risk of hip fracture (a hazard ratio of 2.8). Medscape quoted lead author Kyoung Min Kim, MD, PhD, of the San Francisco Coordinating Center, California Pacific Medical Center Research Institute:

We found that RDW provided a very strong and consistent association with hip and clinical fracture," which means it could be a simple, universal, and powerful measure to identify those at high risk.

Of particular interest is that hip fracture risk and RDW did not correlate with BMD (bone density).

RDW as a biomarker for chronic inflammation

Red blood cell distribution width means that red blood cells, which are produced in the bone marrow from m hematopoietic stem cells, become more variable in size with numerous conditions associated with chronic, non-resolving inflammation in addition to anemia from iron deficiency and B12 deficiency. But anemia was not the key factor.

In a separate finding, despite the known link between anemia and RDW, no significant link was seen between RDW values and hip fracture risk in patients with anemia.

Medscape quotes session co-moderator Elaine W. Yu, MD, director of the Bone Density Center at Massachusetts General Hospital, Boston:

...RDW is associated with many chronic diseases and also with aging, so perhaps it is not surprising that it serves as a marker of skeletal fragility...The fact that RDW is not associated with bone density suggests that perhaps RDW is simply a marker for other comorbidities that increase fracture risk.

In fact, as reported in RDW is an inexpensive but powerful indicator often overlooked on your routine blood test, higher red blood cell distribution width values are associated with all-cause mortality (increased risk of death), cardiovascular disease, inflammatory bowel disease, cancer, lower respiratory infections, and other biomarkers of inflammation. Considering the shared mechanisms, it's not surprising that RDW can predict hip fracture risk. From a cautious functional medicine perspective, RDW becomes suspicious at values above 13%.

Quoting the lead author:

According to our results, RDW shows a very strong and consistent association with risks of hip fractures and all clinical fractures...[and] could have potential value in predicting future fractures.