In a study of 2,609 patients from a pediatric intensive care unit in a children's hospital in Spain, investigators found that more boys than girls were admitted (57.5% vs. 42.5%) but death rates were higher in girls (4.9% vs. 3.3%).

Girls died from a broader range of causes while boys died most often from respiratory and polytraumatic injuries, which could reflect an increased likelihood to engage in risky activities or behave more carelessly, the authors conclude.

"The unexpected female vulnerability that we have found could be partly explained by differences in age and occurrence of nosocomial infection," said Dr. Maria Esther Esteban, senior author of the American Journal of Human Biology study. "This should be explored in future research."

Citation: Esteban, E., Bujaldon, E., Esparza, M., Jordan, I. and Esteban, M. E. (2015), Sex differences in children with severe health conditions: Causes of admission and mortality in a Pediatric Intensive Care Unit. Am. J. Hum. Biol.. doi: 10.1002/ajhb.22709