A quarter of patients admitted to Los Angeles County hospitals are readmitted within 30 days, the highest rate in the state for any county with more than one hospital, according to a recent study.

An analysis by Dexur.com found that the average 30-day readmission rate for more than 100 L.A. County hospitals between October 2015 and September 1016 was 24.5 percent.

This compares with an average readmission rate in California of 20.9 percent, and a nationwide rate of 21.8 percent, according to the New York-based research group. The rates were based on readmissions for any medical cause.

Readmission numbers matter to hospitals, which lose millions in federal Medicare and Medicaid reimbursements for returning patients, hospital industry groups say.

“We obviously strive to do better,” said Jennifer Bayer, vice president of external communications for the Hospital Association of Southern California, of the L.A. County readmissions rate. “But it is not entirely surprising considering the lack of access to primary care and appropriate follow-up care for the underserved.”

By comparison, hospitals in San Mateo County surrounding Silicon Valley had a readmissions rate of 14.8 percent during the same period, according to Dexur.

Of the busiest hospitals in L.A. County, Southern California Hospital at Hollywood readmitted patients at a rate of 36.4 percent, according to the study, while Providence Saint John’s Health Center in Santa Monica had a readmission rate of 15.7 percent.

Health business reporter Dana Bartholomew can be reached at [email protected]. Follow him on Twitter @_DanaBart.