On a rooftop at the University of Maryland at Baltimore, four or five nurses and technicians in scrubs wheel a gurney from the elevator and look skyward. Within minutes, a state police helicopter vectors in with another trauma patient nearing the end of his "golden hour," and it's a rush down to surgeons waiting in the operation room.

That patient is less likely to be a woman than a man, Canadian investigators concluded in a large study of trauma centers.

"Gender-based disparities in access to health care services in general have been recognized for some time and evidence is emerging that these disparities extend to the treatment of severe injuries in trauma centers," Andrea Hill, a post-doctoral fellow at Sunnybrook Health Sciences Centre and the University of Toronto, told media. "Our study confirms and expands on these earlier findings by evaluating the relationship between gender and trauma center care in a large cohort of patients from across Canada."

The research will be presented this week at the American Thoracic Society's international conference in Philadelphia.

In this study of nearly 100,000 Canadians, slightly less than half of women with severe injuries received care at trauma centers compared to 63.2 percent of men, with the disparity also seen in older patients. Among elderly patients with severe, life-threatening injuries, 37.5 percent of women received trauma center care in comparison to nearly half of men.

After adjusting for variables including demographic and socioeconomic factors, in addition to clinical differences in injuries, women were 79 percent as likely to receive the highest level of care as men, with researchers reporting a confidence level of 95 percent in their statistical findings.

The pattern of disparity between men and women was also seen across geographic areas — and essentially any confounding factor the researchers could imagine.

"Our study provides yet more evidence of important gender differences in access to trauma center care for people with severe injuries," Hill said. "Future research should focus on the factors underlying these differences and on the effects of these disparities on patient outcomes."

The study considered 98,871 adult patients with severe injuries, meaning a high likelihood of death within 24 hours of hospitalization, between April 2002 and March 2010. Using multivariable analyses, investigators saw the disparity among men and women in a cohort that included 33,080 women.

The researchers said further study was needed to determine the underlying cause of the disparity.

Hill A, Pinto R, Nathens A, Fowler R. Access To Trauma Centre Care Following Severe Injury: Are Women At A Disadvantage? American Journal of Respiratory and Critical Care Medicine. 2013.