National trends in Staphylococcus aureus infection rates:: Impact on economic burden and mortality over a 6-year period (1998-2003)

Background. We evaluated historical trends in the Staphylococcus aureus infection rate, economic burden, and mortality in US hospitals from 1998 through 2003. Methods. The Nationwide Inpatient Sample was used to assess trends over time of S. aureus infection during 1998 - 2003. Historical trends were determined for 5 strata of hospital stays, including all inpatient stays, surgical procedure stays, invasive cardiovascular surgical stays, invasive orthopedic surgical stays, and invasive neurosurgical stays. Results. During the 6- year study period from 1998 through 2003, the rate of S. aureus infection increased significantly for all inpatient stays (from 0.74% to 1.0%; annual percentage change (APC), 7.1%; P=.004), surgical stays (from 0.90% to 1.3%; APC, 7.9%; P=.001), and invasive orthopedic surgical stays (from 1.2% to 1.8%; APC, 9.3%; P<.001). For invasive neurosurgical stays, the rate of S. aureus infection did not change from 1998 to 2000 but increased at an annual rate of 11.0% from 2000 to 2003 (from 1.4% to 1.8%; P=.034). The total economic burden of S. aureus infection for hospitals also increased significantly for all stay types, with the annual percentage increase ranging from 9.2% to 17.9% (P<.05 for all). In 2003, the total economic burden of S. aureus infection was estimated to be $ 14.5 billion for all inpatient stays and $ 12.3 billion for surgical patient stays. However, there were significant decreases in the risk of S. aureus - related in- hospital mortality from 1998 to 2003 for all inpatient stays ( from 7.1% to 5.6%; APC, - 4.6%;) and for surgical stays (from 7.1% to 5.5%; P=.001 APC, - 4.6%; P=.002). Conclusions. The inpatient S. aureus infection rate and economic burden of S. aureus infections for US hospitals increased substantially from 1998 to 2003, whereas the in- hospital mortality rate decreased.