The relationship between incidence of fractures and anemia in older multiethnic women.

Objectives: To prospectively examine the relationship between anemia and incident fractures of the hip, spine, and all skeletal sites in women from diverse racial and ethnic backgrounds enrolled in the Women's Health Initiative (WHI) Observational Study and Clinical Trials.

Design: Prospective cohort study.

Setting: Forty WHI clinical centers across the United States.

Participants: Postmenopausal women (n=160,080), mean age 63.2±7.2, were recruited and followed for an average of 7.8 years.

Measurements: Anemia was defined as hemoglobin levels at baseline less than 12 g/dL. All fractures were self-reported. Trained physicians further confirmed hip fractures using medical records.

Results: Eight thousand seven hundred thirty-nine of the participants (5.5%) were anemic. The age-adjusted incidence rate of hip fractures per 10,000 person-years was 21.4 in women with anemia and 15.0 in women without anemia; higher incidence rates for spine and all fractures were also observed in anemic women. After multiple covariates were included in the Cox proportional hazards models, significantly greater fracture risk associated with anemia still existed, as demonstrated by hazard ratios of fractures associated with anemia of 1.38 (95% confidence interval (CI)=1.13-1.68) for hip, 1.30 (95% CI=1.09-1.55) for spine, and 1.07 (95% CI=1.01-1.14) for all types. No significant racial or ethnic difference was found in these relationships.

Conclusion: A significantly greater fracture risk was observed in multiethnic postmenopausal women with anemia. Given the high prevalence of anemia in the elderly population, it is important to better understand the relationship and mechanisms linking anemia to fracture risk.