Time to mobilization in hours after surgery for hip fracture and 30-day mortality - A study on 36 229 patients from the Danish Hip Fracture Registry

Background Early mobilization after hip fracture (HF) is a key indicator in national registries and associated with reduced mortality, but in-depth analysis of time in hours for mobilization is lacking. We described the clinical profile and 30-day mortality by time-intervals in hours for mobilization after HF surgery. Methods Using Danish registries, we included HF patients aged ≥65 years (from year 2016-2021). Exposure - time in hours from start of surgery to mobilization. Outcome - mortality within 2-30 days of surgery. Primary mortality analysis - we compared mobilizations >24-36 hours versus ≤24 hours by calculating weighted risks, risk differences (RDs) and hazard ratios (HRs) using inverse probability of treatment weighted method. Secondary mortality analyses - we compared mobilizations >24-36 hours and >12-24 hours versus ≤12 hours. Results We included 36,229 patients (67.3% women) with a median age of 82.6 years. Patients mobilized ≤24 hours had a similar age, body mass index, and marital status, but were slightly more living in own residence, have high prefracture mobility, high education, and less comorbidity than patients mobilized >24-36 hours. The weighted risk of 30-day mortality for mobilization >24-36 hours versus ≤24 hours was 9.67% and 8.00% with corresponding RD and HR of 1.67% (0.54, 2.80) and 1.22 (1.07, 1.38). The weighted RD and HR were 1.62% (0.89, 2.35) and 1.25 (1.12, 1.39) for >12-24 versus ≤12 hours, and 1.33% (0.17-2.49) and 1.16 (1.02, 1.31) for >12-24 hours versus >24-36 hours. Conclusions The 30-day mortality increases with the increasing time to mobilization after HF surgery. We suggest focusing on time in hours to mobilization with a 24-hour or even earlier timepoint after surgery.