While nurse aides (NAs) provide the majority of direct care to nursing home residents, efforts to improve quality have focused more on increasing professional nursing staff. The care provided by NAs is nontechnical and consists primarily of helping residents with activities of daily living (ADLs) such as eating, dressing, bathing, toileting, and walking (Cawley, Grabowski, and Hirth 2006
). When NAs provide direct care, RNs observe, assess, and record resident symptoms and progress. RNs also collaborate with physicians in treatment, administration of medications, and development of care plans.
Existing evidence supports that RN hours may be more important than total nursing hours per resident. In a study using a nationally representative sample of nursing homes and residents, Cohen and Spector (1996)
found that a higher RN intensity was associated with a lower rate of mortality; however, having more NAs had no impact on resident outcomes. Horn et al. (2005)
found that more RN hours were associated with fewer pressure ulcers, hospitalizations, and urinary tract infections (UTIs); less weight loss, catheterization, and deterioration in the ability to perform ADLs; and greater use of nutritional supplements, while more NA hours were associated only with fewer pressure sores.
Using Online Survey, Certification and Reporting (OSCAR) data from 1992 to 1997, Castle (2000)
found that facilities with more RNs per 100 beds were less likely to increase restraint use. Harrington, Zimmerman et al. (2000)
examined the relationship between staffing hours per resident-day and facility deficiencies identified by state surveyors under federal certification regulations. Consistent with previous research, fewer RN hours was associated with more quality of care deficiencies. More recently, Decker (2006)
used National Nursing Home Survey Data from 1999 to show that RN staffing levels were associated with faster discharge to the community for short-stay residents requiring primarily postacute care but not for long-stay residents.
Due to the difficulty in finding adequate numbers of qualified staff or the desire to minimize costs, some facilities may hire fewer than the optimal number of RNs or may shift some tasks typically done by RNs to less qualified nursing staff, which may have implications for resident outcomes. Using a sample of 1,287 nursing homes in five states, Weech-Maldonado et al. (2004)
found that greater use of RNs, both in absolute terms and relative to total nursing staff, was associated with a reduced likelihood of pressure ulcers, better cognitive functioning, and lower use of restraints. This finding suggests that staff mix may be as important as the level, and that efforts to improve quality should focus on increasing the proportion of professional staff as well as RN staff intensity.
In summary, most evidence indicates that more RN staffing, both in an absolute sense and as a proportion of total hours, is associated with better outcomes. The cross-sectional research, however, is subject to omitted variable bias, and most studies except Cohen and Spector (1996)
are subject to possible bias from reverse causality. Therefore, mandating and enforcing higher staffing ratios could have no effect on outcomes. Little longitudinal evidence is available. Zhang and Grabowski (2004)
used longitudinal OSCAR data to look at whether the Nursing Home Reform Act improved both staffing and quality. Implementation of this act was shown to increase staffing, but the staffing increases were not associated with improvements in quality except in homes that were of particularly poor quality at baseline. The facility-level measures of quality available in OSCAR may be insufficiently sensitive, and endogeneity of staffing and outcomes was not addressed. The use of a longitudinal model in a recent study of the effect of hospital staffing on mortality was shown to result in substantially smaller estimates than those from cross-sectional research (Mark et al. 2004
), with a larger RN effect when endogeneity was addressed.
We therefore model resident-level outcomes using a longitudinal model with facility fixed effects and instrumental variables to correct for endogeneity. The fixed-effects model, which controls for any omitted time-invariant facility-level variables, gives us the effect of a change in RN staffing and skill mix on a change in outcomes. While the fixed-effects model is an improvement over cross-sectional analyses, it does not control for any omitted time-varying variables or address all potential endogeneity of staffing and outcomes. We view the staffing decision as inherently endogenous. That is, facility managers make structural decisions about staffing (both intensity and skill mix) and the quality of care to be provided subject to regulations, resource constraints, and current and expected case-mix. At the same time, these decisions affect resident outcomes. Because facilities with sicker residents would tend to opt for higher staffing, the endogeneity bias would tend to underestimate the effect of staffing on outcomes. We therefore expect that accounting for this endogeneity through instrumental variables will result in estimates of larger magnitude than in a longitudinal model without adjustment for endogeneity.