Associations of sex, Alzheimer's disease and related dementias, and days alive and at home among older Medicare beneficiaries recovering from hip fracture

Background: Males constitute 25% of older adults who experience hip fractures in the United States; a concerning upward trend given poorer health and outcomes among male survivors. Male sex is associated with worse cognitive performance after hip fracture, impacting participation in rehabilitation and long-term outcomes especially for those with Alzheimer's disease or related dementias (ADRD). However, little research has evaluated whether sex differences in post-fracture recovery are greater among those living with ADRD. Methods: Data were drawn from 2010 to 2017 Medicare fee-for-service beneficiaries aged 65 years and older who survived hospitalization for hip fracture (n = 69,581). The primary outcome was days alive and at home (DAAH), a validated patient-centered claims-based outcome calculated as 365 days from fracture minus days in hospital, nursing home, rehabilitation facility, emergency department, or time after death. Multivariable Poisson regressions with an interaction term between sex and ADRD status were to model the association between DAAH and ADRD in the 12 months post hip fracture, adjusting for demographics, injury severity, chronic disease burden, and hospital-level fixed effects. Results: Compared to females, males were younger and had more comorbidities at the time of fracture. Among survivors, males with ADRD spent a mean of 160.7 DAAH compared to 228.4 for males without ADRD, 177.8 for females with ADRD, and 248.0 for females without ADRD. In adjusted analyses, males without ADRD spent 8.2% fewer DAAH compared to females (rate ratio [RR] = 0.92, 95% CI 0.92-0.92). This relative sex difference increased significantly when comparing those living with ADRD, with males spending an additional 3.3% fewer DAAH (interaction RR = 0.96, 95% CI 0.96-0.97). Conclusions: Males spend fewer DAAH after hip fracture than females, and this difference increases modestly for males living with ADRD compared to females. This suggests that cognitive impairment may be a small but significant contributor to sex-based differences observed during hip fracture recovery.