Persistent changes in interleukin-6 and lower extremity function following hip fracture

Background. A hip fracture often heralds a period of functional decline in elderly persons. Although an inflammatory reaction would be expected following a hip fracture, whether the degree of this response is associated with adverse functional outcomes is unknown. Methods. In a cohort from the Baltimore Hip Studies, women aged 65 years or older with a hip fracture were evaluated at 3 or 10 days (baseline) and 2, 6, and 12 months (follow-up) postfracture. Serum was analyzed for interleukin-6 (IL-6) level. A score of timed performance of 9 tasks, the Lower Extremity Gain Scale (LEGS) was calculated at each evaluation. We divided participants into tertiles based on their cytokine levels at 2, 6, and 12 months, and examined the LEGS score trajectories as a function of IL-6 tertile using generalized estimating equations, adjusting for age, prefracture function, body fat, pain, cognitive function, type of surgical repair, the number of in-hospital complications, and the number of comorbid medical conditions. Results. At baseline, 2, 6, and 12 months, respectively, 149, 95, 101, and 82 participants provided serum samples; of these participants 65, 78, and 59 also provided a LEGS measure at 2, 6, and 12 months, respectively. At 12 months postfracture the median (interquartile range) of serum IL-6 levels was 7.4 (4.0, 15.9) pg/mL. Participants in the lowest tertile of IL-6 level performed better on the LEGS than did those in the highest tertile (p = .008). At 12 months postfracture, participants in the lowest tertile scored 5.3 points better (95% confidence interval, 2.0-8.6) on the LEGS than did those in the highest terfile (p = .002). Conclusions. Higher IL-6 levels are adversely associated with recovery of lower extremity function after hip fracture. Factors that predict cytokine response and the potential mechanisms by which this effect is mediated warrant further study.