Hemoglobin and hip fracture risk in older non-Hispanic white adults.

SUMMARY: The relationship between hemoglobin and hip fracture was examined in older non-Hispanic white adults from the third National Health and Nutrition Examination Survey (NHANES III). Both low and high hemoglobin values were associated with increased hip fracture risk before and after adjusting for selected risk factors.

INTRODUCTION: The few studies to date that have examined the relationship between hemoglobin and fracture risk have focused on low hemoglobin values. The present study examined hip fracture risk across the hemoglobin distribution in older non-Hispanic white adults from the third National Health and Nutrition Examination Survey (NHANES III, 1988-1994).

METHODS: Hemoglobin was measured using a Coulter S-plus Jr.® (Coulter Electronics, Hialeah, FL) in 2,122 non-Hispanic whites age 65 years and older. Hip fracture cases were identified using linked Medicare and mortality records obtained through 2007. Cox proportional hazards models were used to assess the best-fitting model and to estimate the hazards ratio (HR) for hip fracture by hemoglobin decile before and after adjusting for selected confounders.

RESULTS: There were 239 hip fracture cases in the analytic sample. The best fitting model was quadratic. When compared to values in the middle of the distribution, those with hemoglobin in the lowest and highest deciles had increased hip fracture risk (HRlowest decile = 2.96, 95 % confidence interval (CI) 1.44-6.08; HRhighest decile = 2.06, 95 % CI 1.09-3.92) after adjusting for age and sex. Both HRs remained significant after adjusting for additional confounders (HRlowest decile = 2.24, 95 % CI 1.09-3.92; HRhighest decile = 2.37, 95 % CI 1.35-4.16).

CONCLUSIONS: Both low and high hemoglobin values were associated with increased hip fracture risk. The mechanism underlying the relationship is not clear, but there were some suggestions that it may differ for low versus high hemoglobin.