Serum Vitamin E Concentrations and Physical Function after Hip Fracture

Abstract

Background: Malnutrition after hip fracture is common and may contribute to the steep decline and protracted recovery of physical function post-fracture. Deficiencies in protein and total caloric intake have been consistently associated with adverse outcomes, but less is known about micronutrient deficiencies during recovery from hip fracture. Low concentrations of vitamin E have been associated with incident decline in physical function among older adults and may therefore be of particular importance to hip fracture patients. Methods: Serum concentrations of α- and γ-tocopherol, the two major forms of vitamin E, were measured in female hip fracture patients from the Baltimore Hip Studies cohort 4 (BHS4) at baseline and 2, 6, and 12 month post-fracture follow-up visits. Linear regression and generalized estimating equations (GEE) were used to determine predictors of vitamin E concentrations at baseline and throughout recovery, respectively. Linear regression was used to perform adjusted comparisons of baseline vitamin E concentrations among BHS 4 participants to those of similar populations of older women from the Women's Health and Aging Study I, InCHIANTI, and the National Health and Nutrition Examination Surveys. Four physical function measures - Six Minute Walk Distance (6MWD), Lower Extremity Gain Scale (LEGS), SF-36 Physical Functioning Domain (SFPF), and Yale Physical Activity Survey (YPAS) - were assessed in BHS4 at 2, 6, and 12 months post-fracture. GEE and marginal structural modeling were used to model the relationship between baseline and time-varying vitamin E concentrations, respectively, and physical function after hip fracture. Results: Serum vitamin E concentrations among 148 female hip fracture patients aged ≥ 65 years were studied. Mean α-tocopherol concentrations were lowest at baseline, and time from fracture to blood draw was strongly and positively associated with baseline α-tocopherol (p=0.005). Cognitive function was positively associated with α-tocopherol at baseline (p=0.002) and throughout recovery (p=0.05). Mean γ-tocopherol concentrations did not change appreciably throughout the year after fracture, but there were drastic fluctuations in concentrations within individuals. An inverse relationship was noted between α- and γ-tocopherol (p=0.0009), but some factors were negatively associated with both forms of vitamin E including current smoking status (α-: p=0.02, γ-: p=0.01) and Lower Extremity Physical Activities of Daily Living (α-: p=0.02, γ-: p=0.01). In the adjusted comparison of 1,161 older women, serum concentrations of both forms of vitamin E were highest among BHS4 participants (p < 0.0001). Baseline vitamin E concentrations in BHS4 were positively associated with 6MWD and YPAS (p < 0.007) and time-varying vitamin E was positively associated with 6MWD, LEGS, YPAS, and SFPF (p < 0.03). Conclusions: Though adjusted comparisons to older women with no history of hip fracture did not reveal lower vitamin E concentrations among hip fracture patients, α-tocopherol was lowest among hip fracture patients shortly after the injury. Highly cognitively and physically functioning hip fracture patients demonstrated higher vitamin E concentrations throughout recovery from hip fracture. Consequently, the relatively high degree of function among the BHS4 cohort may explain the higher than expected vitamin E concentrations uncovered among the hip fracture patients. Despite the high level of function in this cohort, serum concentrations of both α- and γ-tocopherol were associated with better physical function after hip fracture. These micronutrient markers of a healthy diet may thus represent a potentially modifiable factor for recovery of post-fracture physical function.