Objective. To assess longitudinally whether a change in registered nurse (RN) staffing and skill mix leads to a change in nursing home resident outcomes while controlling for the potential endogeneity of staffing.
Data Sources. Minimum Data Set (MDS) nursing home resident assessment data from five states merged with Online Survey Certification and Reporting (OSCAR) data from 1996 through 2000.
Study Design. Resident-level longitudinal analysis with facility fixed effects and instrumental variables. Outcomes studied are incidence of pressure sores and urinary tract infections. RN staffing was measured as the care hours per resident-day and skill mix was measured as RN staffing hours as a proportion of total staffing hours.
Data Extraction Method. We use all quarterly MDS assessments that fall within 120 days of an annual OSCAR data point, resulting in 399,206 resident-level observations.
Principal Findings. Controlling for endogeneity of staffing increases the estimated impact of staffing on outcomes in nursing homes. Greater RN staffing significantly decreases the likelihood of both adverse outcomes. Increasing skill mix only reduces the incidence of urinary tract infections.
Conclusions. Research that fails to account for endogeneity of the staffing–outcomes relationship may underestimate the benefit from increased RN staffing. Increases in RN staffing are likely to reduce adverse outcomes in some nursing homes. More research using a broader array of instruments and a national sample would be beneficial.