Nurse-staffing levels and the quality of care in hospitals.

BACKGROUND It is uncertain whether lower levels of staffing by nurses at hospitals are associated with an increased risk that patients will have complications or die. METHODS We used administrative data from 1997 for 799 hospitals in 11 states (covering 5,075,969 discharges of medical patients and 1,104,659 discharges of surgical patients) to examine the relation between the amount of care provided by nurses at the hospital and patients' outcomes. We conducted regression analyses in which we controlled for patients' risk of adverse outcomes, differences in the nursing care needed for each hospital's patients, and other variables. RESULTS The mean number of hours of nursing care per patient-day was 11.4, of which 7.8 hours were provided by registered nurses, 1.2 hours by licensed practical nurses, and 2.4 hours by nurses' aides. Among medical patients, a higher proportion of hours of care per day provided by registered nurses and a greater absolute number of hours of care per day provided by registered nurses were associated with a shorter length of stay (P=0.01 and P<0.001, respectively) and lower rates of both urinary tract infections (P<0.001 and P=0.003, respectively) and upper gastrointestinal bleeding (P=0.03 and P=0.007, respectively). A higher proportion of hours of care provided by registered nurses was also associated with lower rates of pneumonia (P=0.001), shock or cardiac arrest (P=0.007), and "failure to rescue," which was defined as death from pneumonia, shock or cardiac arrest, upper gastrointestinal bleeding, sepsis, or deep venous thrombosis (P=0.05). Among surgical patients, a higher proportion of care provided by registered nurses was associated with lower rates of urinary tract infections (P=0.04), and a greater number of hours of care per day provided by registered nurses was associated with lower rates of "failure to rescue" (P=0.008). We found no associations between increased levels of staffing by registered nurses and the rate of in-hospital death or between increased staffing by licensed practical nurses or nurses' aides and the rate of adverse outcomes. CONCLUSIONS A higher proportion of hours of nursing care provided by registered nurses and a greater number of hours of care by registered nurses per day are associated with better care for hospitalized patients.