Jill R. Horwitz, Neil S. Wenger, David P. Powell, José J. Escarce, Lee A. Jennings, L L Liang, Punam Parikh, David S. Zingmond
Importance: A central goal of medical malpractice law is to ensure quality of care by deterring negligent treatment. Although previous research has produced mixed results, much of it finds no clear association between liability exposure and medical treatment. During the COVID-19 pandemic, many states adopted immunity from tort liability for harms to nursing home residents, creating a natural experiment. Objective: To examine the association between immunity from tort liability and nursing home staffing. Design, Setting, and Participants: This cohort study using a difference-in-differences model evaluated all US nursing homes reporting data from 2018 to 2023. The data analysis took place between July 2025 to September 2025. Exposure: State tort immunity law. Main Outcomes and Measures: Nursing home staffing patterns derived from Centers for Medicare & Medicaid Services Nursing Home Compare, Payroll Based Journal Daily Staffing Averages, and weekly nursing home COVID-19 tracking data. Results: During the COVID-19 pandemic, approximately 80% of the US states abruptly implemented some form of tort immunity for nursing homes. Of 13 205 nursing homes in the analysis, 11 382 (86.2%) were subject to tort immunity and 1823 (13.8%) were not. Some of the laws included automatic end dates and others were indefinite. Nursing homes immune from tort liability exhibited less staff time per patient per day than nursing homes in states that did not grant tort immunity: a 2.5-percentage point (pp) reduction (95% CI, -4.3 to -0.6 pp) in overall daily staffing hours and a 1.2-pp reduction (95% CI, -2.3 to -0.1 pp) in overall staffing hours per patient per day with significant reduction in certified nursing assistant hours to patient per day (-2.0 pp; 95% CI, -3.5 to -0.5 pp). Conclusions and Relevance: In this cohort study of US nursing homes, the introduction of immunity was associated with decreased overall nursing home staffing and staff per resident time. Registered nurse and licensed practical nurse to patient time was not statistically different.