Liu C (Seattle Center of Excellence (COE)), Li Y
(Seattle COE), Sharp N
(Seattle COE), Lowy E
(Seattle COE), Maciejewski M
(Durham COE), Sales A
(University of Alberta), Needleman J
Previous research indicates a positive relationship between nurse staffing and total patient care costs. However, total patient care costs include administrative overhead and fixed costs not directly related to patient care and thus unaffected by nurse staffing. This study examines the relationships between nurse staffing and direct inpatient care costs in acute medical/surgical units.
This cross-sectional study includes all admissions (139,361) to 292 acute medical/surgical units in 125 VAMCs between 2/03-6/03. Data sources were DSS inpatient and ALB extracts, VA administrative databases, and national databases on market/health service area characteristics. Nurse staffing measures included total nursing hours per patient day (HPPD) and the proportion of RN to total nursing hours (RN skill mix) at the unit level. Direct patient care costs were variable direct costs for non-nursing and non-surgical services. We analyzed data using two-step multi-level mixed models. In step 1, we regressed the direct patient care cost on patient, facility, and market characteristics to obtain a predicted cost. In step 2, we regressed direct patient care cost on predicted cost and nurse staffing variables. The same analytical approach was used for cost per day and length of stay as the dependent variable.
The average direct patient care cost was $2,455/admission (SD=$4,309), which accounted for 26.9% of total cost. The average cost per day was $459 (SD=$600). The average length of stay was 5.8 days (SD=7.2). RN skill mix and total nursing HPPD had an average of 58% (SD=14%) and 7.2 hours (SD=1.8), respectively. The multivariate analyses show that nurse staffing measures were positively associated with cost per day (p < 0.001); but not significantly associated with cost per admission. Nurse staffing measures were negatively associated with length of stay (p < 0.001).
The non-nursing and non-surgical variable direct costs account for only one quarter of total costs per admission. Higher nurse staffing levels are related to increases in direct patient cost per day, but not to direct patient cost per admission, where the effects of increased cost per day are mediated by shorter lengths of stay.
Using appropriate cost measures is critical in examining the relationship between nurse staffing and patient care costs.