Associations of hemoglobin and change in hemoglobin with risk of incident hip fracture in older men and women: the cardiovascular health study

Summary: In a multi-site longitudinal cohort study, decreasing hemoglobin was associated with increased hip fracture risk in men. Anemia was associated with hip fracture in men and in African American women. Decreasing hemoglobin may be a marker of progressing bone fragility, making its serial measurement useful for fracture risk stratification. Introduction: Hematopoiesis and bone health are interdependent. Anemia has been associated with risk of fracture in humans. To further elucidate this relationship, we hypothesized that decreasing hemoglobin could indicate defective hematopoiesis and would also predict fracture risk. Methods: We performed a prospective analysis from study baseline (1992) of the Cardiovascular Health Study, a multi-site longitudinal cohort study. A total of 4670 men and women, ages >65 years, who were able to consent and not institutionalized or wheelchair bound, had hemoglobin (Hb) measured in 1992. For 4006 subjects, Hb change from 1989 to 1992 was annualized and divided into sex-specific quartiles. Incident hip fractures were verified against Medicare claims data during a median follow-up of 11.8 years. Results: Nested Cox proportional-hazard models estimated association of hip fracture with anemia (men Hb <13 g/dL, women Hb <12 g/dL) and separately, greatest Hb decrease (versus others). Anemia was associated with increased hip fracture risk in all men (HR 1.59; 95% CI 1.01–2.50) and African American women (HR 3.21; 95% CI 1.07–9.63). In men, an annualized Hb loss of >0.36 g/dL/year was associated with a higher risk of hip fracture (HR 1.67; 95% CI 1.10–2.54), which was lessened by anemia at the start of fracture follow-up (HR 1.53; 95% CI 0.99–2.39). Conclusions: Decreasing Hb may be an early marker for subsequent hip fracture risk in men, which may be less informative once an anemia threshold is crossed. Only African American women with anemia had increased hip fracture risk, suggesting a race difference in this relationship.