Characterization of the gender dimorphism after injury and hemorrhagic shock: Are hormonal differences responsible?

OBJECTIVE:: To characterize the gender dimorphism after injury with specific reference to the reproductive age of the women (young, <48 yrs of age, vs. old, >52 yrs of age) in a cohort of severely injured trauma patients for which significant variation in postinjury care is minimized. DESIGN:: Secondary data analysis of an ongoing prospective multicenter cohort study. SETTING:: Academic, level I trauma and intensive care unit centers. PATIENTS:: Blunt-injured adults with hemorrhagic shock. INTERVENTIONS:: None. MEASUREMENTS AND MAIN RESULTS:: Separate Cox proportional hazard regression models were formulated based on all patients to evaluate the effects of gender on mortality, multiple organ failure, and nosocomial infection, after controlling for all important confounders. These models were then used to characterize the effect of gender in young and old age groups. Overall mortality, multiple organ failure, and nosocomial infection rates for the entire cohort (n = 1,036) were 20%, 40%, and 45%, respectively. Mean Injury Severity Score was 32 ± 14 (mean ± sd). Men (n = 680) and women (n = 356) were clinically similar except that men required higher crystalloid volumes, more often had a history of alcoholism and liver disease, and had greater ventilatory and intensive care unit requirements. Female gender was independently associated with a 43% and 23% lower risk of multiple organ failure and nosocomial infection, respectively. Gender remained an independent risk factor in young and old subgroup analysis, with the protection afforded by female gender remaining unchanged. CONCLUSIONS:: The independent protective effect of female gender on multiple organ failure and nosocomial infection rates remains significant in both premenopausal and postmenopausal women when compared with similarly aged men. This is contrary to previous experimental studies and the known physiologic sex hormone changes that occur after menopause in women. These results suggest that factors other than sex hormones may be responsible for gender-based differences after injury.