For some patients, shorter hospital stays aren't better.

A study of 15,531 Pennsylvania patients diagnosed with a pulmonary embolism - a life-threatening condition in which a blood clot blocks a vessel in the lungs - found that those discharged more quickly were at greater risk of death.

The researchers, from Pittsburgh and Switzerland, examined hospital billing data from the Pennsylvania Health Care Cost Containment Council. They found that the patients who were discharged after four or fewer days were significantly more likely to die than those who remained in the hospital for five, six or more days.

The study sought to determine whether new guidelines that recommend patients identified as being at low-risk for complications be discharged more quickly were working as intended.

They weren't.

More than half of those discharged after four days or less had more severe cases, the researchers found.

Writing in the current Archives of Internal Medicine, they concluded that "physicians may inappropriately select patients with [pulmonary embolism] for early discharge who are at increased risk of complications."