Sex-Related Differences in Functional and Neurological Outcomes of Spinal Cord Injury.

Background and objectives: Traumatic spinal cord injury (SCI) tends to occur in different demographics and with differing etiology between males and females. Sex-related differences may influence recovery, but there remains a lack of evidence on this subject. Our objective was to quantify the influence of sex on functional and neurological outcomes of SCI.

Methods: This was a retrospective cohort study of the multicenter, prospectively maintained SCI Model Systems database from 1992 to 2016. Traumatic SCI patients (≥15 years old) enrolled in a participating inpatient rehabilitation center within 30 days of injury with follow-up at 1 year were included. The primary outcome was the Functional Independence Measure (FIM), which quantifies independence in 13 activities of daily living. Secondary outcomes were individual FIM items, American Spinal Injury Association (ASIA) Motor Index Score at 1 year postinjury, and improvement in ASIA Impairment Scale (AIS). The impact of sex on each outcome was evaluated using propensity score-weighted multivariable regression analyses while controlling for covariates such as age, injury severity, and baseline function.

Results: The analysis included 3924 patients (20% female). Multivariable linear regression showed that female sex was associated with worse FIM scores at 1 year postinjury (B = -3.1, 95% CI: -4.4 to -1.8). The FIM items with the greatest differences in independence between males and females were bladder management and transfers, which favored males. For ASIA Motor Score, while females had 10-point greater absolute scores at 1 year (P = .03) and 2-point greater improvement (P = .03) compared with males, no effect was present after adjusting for confounding variables in multivariable regression. The rate of ASIA Impairment Scale improvement was higher in females (P = .04), but this was not significant in multivariable regression (odds-ratio: 1.25, 95% CI: 0.96-1.63).

Conclusion: Male sex is associated with greater functional independence, despite equal or greater motor recovery in female patients. Female SCI patients may benefit from targeted interventions to improve independence.