Invisible staffing churn in nursing homes: CMS turnover metrics miss a growing short-term workforce.

Introduction: Federal policy mandates adequate nursing home (NH) staffing, yet staffing adequacy remains difficult to define and measure. In 2022, the Centers for Medicare & Medicaid Services (CMS) incorporated annual turnover into Five-Star Ratings but adopted a definition excluding staff below a 120-hour-in-90-days threshold, potentially underestimating turnover and weakening validity. Methods: Using Payroll-Based Journal and CareCompare data (2020Q2-2024Q1), we replicated CMS-reported turnover and constructed an inclusive measure counting new hires. We assessed divergence between definitions, associations with ten standardized CMS quality indicators, and changes in facility rankings. Results: By 2022-2023, 45% of nursing hires were excluded under CMS's definition. As short-term staffing increased, CMS-specification and inclusive turnover diverged (correlation 0.91-0.82). Associations with quality outcomes were modest and similar across definitions. However, facility rankings differed substantially: only 30% of facilities remained in the same turnover decile, with reclassification concentrated among NHs with high short-term attrition, greater contract use, and distinct ownership and payer mix. Conclusion: CMS turnover metrics miss nearly half of turnover, understating instability and reshaping facility comparisons without improving associations with quality outcomes. As short-term staffing expands, the CMS measure risks becoming less informative about workforce instability, underscoring how metric definitions shape oversight and reporting.