Patients who lack health insurance are more likely to die from car wrecks and other traumatic injuries than people who belong to a health plan, even though emergency rooms are required to care for all patients. regardless of ability to pay, according to a study to be published today.

An analysis of 687,091 patients who visited trauma centers nationwide between 2002 and 2006 found that the odds of dying after an accidental injury were nearly twice as high for the uninsured than for patients with private insurance, researchers reported in Archives of Surgery.

Trauma physicians said they were surprised by the findings, even though a slew of studies had previously documented the ill effects of going without health coverage. Uninsured patients are less likely to be screened for certain cancers or be admitted to specialty hospitals for procedures such as heart bypass surgery.

They also often wait longer to see doctors in ERs.

And patients without insurance may have higher rates of untreated underlying conditions that make it harder to recover from trauma injuries, the research team from Harvard University and Brigham and Women’s Hospital in Boston said. They also may be more passive with doctors and nurses because they don’t interact with them as often.

Overall, about 18,000 deaths each year have been traced to a lack of health insurance.