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Level of HMO penetration in a hospital's market affects the relationships between nurse staffing, length of stay, and mortality

Increased registered nurse (RN) staffing for hospitals in markets with higher health maintenance organization (HMO) penetration is associated with lower patient mortality and length of stay (LOS) ratios. However, this is not the case for hospitals in low HMO penetration markets, according to a study supported by the Agency for Healthcare Research and Quality (HS10153).

Barbara A. Mark, Ph.D., of the University of North Carolina School of Nursing, and colleagues used administrative data from 422 acute care hospitals and a theoretical model to examine whether managed care penetration affected the relationships between changes in nurse staffing and changes in quality of care from 1990 to 1995. For hospitals in markets with over 28 percent of people enrolled in HMOs, increasing nurse staffing significantly reduced the mortality and LOS ratios at the 25th percentile of nurse staffing, and reduced LOS ratios at the 50th percentile, but had no effect on mortality and an insignificant effect on LOS at the 75th percentile.

None of the estimation methods showed a significant effect of nurse staffing on mortality ratio or length of stay for hospitals in low HMO penetration markets (less than 7.5 percent of people enrolled). Hospitals in high HMO penetration markets may have adopted a range of cost control mechanisms and restructured nursing work to maximize nursing time and cost-efficiency. These changes may have reduced slack resources, making the effects of increased nurse staffing on reduced LOS and mortality ratios more readily discernible, note the researchers.

See "The impact of HMO penetration on the relationship between nurse staffing and quality," by Dr. Mark, David W. Harless, M.D., and Michael McCue, D.B.A., in the July 2005 Health Economics 14, pp. 737-753.

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