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## Statistics in the News: Chapter 17 Multiple Regression and Correlation

Nurse Staffing Levels and the Quality of Hospital Care

Using 1997 data for 799 hospitals in 11 states (covering over 5 million discharges of medical patients and over 1 million discharges of surgical patients), researchers examined the relation between the amount of care provided by nurses at hospitals and patients' outcomes. They conducted ordinary least squares regression analysis, controlling for patients' risk of adverse outcomes, differences in the nursing care needed for each hospital's patients, and other variables.

Medical patients. Among (nonsurgical) medical patients, a higher proportion of hours of care per day provided by registered nurses (rather than licensed practical nurses and nurses' aides) was associated with a shorter length of stay, as well as lower rates of urinary tract infections and upper gastrointestinal bleeding, of pneumonia, shock or cardiac arrest, and of "failure to rescue." (The latter was defined as death from upper gastrointestinal bleeding, sepsis, deep venous thrombosis, pneumonia, shock or cardiac arrest-all of these being conditions that might be reversed if treated in time, which, in turn, depends on whether skilled nurses are present to judge early whether patients are recovering normally.)

Crucial results are summarized in Tables A and B.

TABLE A Effects of Increasing Proportion of Medical Patient Care Hours Supplied by Registered Nurses (RNs) from 25th to 75th Percentile

TABLE B Effects of Increasing Number of RN Hours Per Medical Patient Day

Surgical patients. Among surgical patients, a higher proportion of hours of care per day provided by registered nurses (rather than licensed practical nurses and nurses' aides) was associated with lower rates of urinary tract infections. A greater absolute number of hours of care per day provided by them was associated with lower rates of "failure to rescue."

Crucial results are summarized in Tables C and D.

TABLE C Effects of Increasing Proportion of Surgical Patient Care Hours Supplied by Registered Nurses (RNs) from 25th to 75th Percentile

TABLE D Effects of Increasing Number of RN Hours Per Surgical Patient Day

Conclusion: A higher proportion of hours of nursing 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. Said Dr. Jack Needleman, lead author of the study, "I estimate that hundreds or, perhaps, thousands of deaths each year are due to low staffing."

Sources: Adapted from Jack Needleman et al., "Nurse Staffing Levels and the Quality of Care in Hospitals," The New England Journal of Medicine, May 30, 2002, pp. 1715-1722, and Denise Grady, "Number of Nurses Affects Many Illnesses, Study Finds," The New York Times, May 30, 2002, p. A14.

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