Hemoglobin and transferrin saturation are associated with mobility and physical function two months after hip fracture surgery: an observational cohort study

PURPOSE: To investigate whether hemoglobin two days after discharge and transferrin saturation two months after discharge for hip fracture (HF) were associated with mobility and functional outcomes. METHODS: We included patients ≥ 65 years, surgically treated for a hip fracture at Copenhagen University Hospital, Bispebjerg and Frederiksberg. Iron deficiency was defined as transferrin saturation (TSAT) below 20%. Mobility and physical function were measured two months after discharge in an orthogeriatric outpatient clinic using new mobility score (0-9 points, 9 best functional mobility), six-minute walk test, usual walking speed (10-m), 30-s Sit-to-Stand test, and handgrip strength. Associations between hemoglobin, transferrin saturation (per units of 10%) and outcomes were evaluated by multivariable linear regression, with age, sex, and type of fracture (intra- versus extracapsular) as covariates. RESULTS: 235 patients were included (69% women, age 80 ± 8 years, 55% had intra-capsular fractures). The average ± SD hemoglobin two days after discharge was 10.4 ± 1.5 g/dL, 91% had anemia according to the WHO definition. The average transferrin saturation two months after surgery was 0.21 ± 0.09, 51% had iron deficiency. High hemoglobin was associated with high new mobility score (B = 0.46, 95% CI 0.25-0.66, p < 0.001). High transferrin saturation was associated with high new mobility score (B = 0.74, 95% CI 0.17-1.31, p = 0.01), six-minute walk test (B = 47, 95% CI 16-78, p = 0.004), walking speed (B = 0.12, 95% CI 0.06-0.19, p < 0.001), 30-s Sit-to-Stand test (B = 1.56, 95% CI 0.30-2.85, p = 0.01), and hand grip strength (B = 2.1, 95% CI 0.0-4.2, p = 0.049). CONCLUSIONS: High hemoglobin two days after discharge was associated with high new mobility score two months after surgery. Transferrin saturation was associated with mobility and all measured functional outcomes two months after hip fractures.