News Release

Debunking the 'July effect': Surgery date has little impact on outcome, Mayo Clinic finds

Data from nearly 1 million spine surgeries may help refute long-held belief

Peer-Reviewed Publication

Mayo Clinic

ROCHESTER, Minn. -- The "July Effect" -- the notion that the influx of new residents and fellows at teaching hospitals each July makes that the worse time of year to be a patient -- seems to be a myth, according to new Mayo Clinic research that examined nearly 1 million hospitalizations for patients undergoing spine surgery from 2001 to 2008. Among those going under the knife, researchers discovered that the month surgery occurred had an insignificant impact on patient outcomes.

In addition, no substantial "July Effect" was observed in higher-risk patients, those admitted for elective surgery or patients undergoing simple or complex spinal procedures. The research was published online Tuesday in Journal of Neurosurgery: Spine.

"We hope that our findings will reassure patients that they are not at higher risk of medical complications if they undergo spinal surgery during July as compared to other times of the year," says study co-author Jennifer McDonald, Ph.D., a Mayo Clinic radiologist. "While we only looked at spinal surgeries, we think it's likely we'd find similar outcomes among other surgeries and procedures."

Researchers analyzed 2001 to 2008 data in the Nationwide Inpatient Sample, a large public database of information on hospitalized U.S. patients.

The researchers found that the incidents of all outcomes studied were higher in teaching hospitals, those with residents and fellows, than in nonteaching hospitals. In the teaching hospitals, minimally higher rates of postoperative infection and patient discharge to a long-term facility were found during July when compared with other months, but they were not high enough to establish a "July Effect."

In-hospital deaths and postoperative complications did not differ according to the month of admission, the study found.


About Mayo Clinic

Mayo Clinic is a nonprofit worldwide leader in medical care, research and education for people from all walks of life. For more information, visit and

Journalists can become a member of the Mayo Clinic News Network for the latest health, science and research news and access to video, audio, text and graphic elements that can be downloaded or embedded.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.