Nurse Understaffing Linked to Higher Mortality, Readmissions

Patients exposed to nurse understaffing are more likely to experience higher rates of in-hospital mortality and 30-day readmission rates. These findings, published in JAMA Network Open, underscore the importance of proper nurse staffing adherence to improve patient outcomes.¹

The findings from this new study are consistent with previous research across Europe, the US, Finland, and Switzerland demonstrating that low nurse staffing levels are associated with missed care.¹ More recently, nurses in New York went on strike due to unfair treatment by their hospital systems, and one of their primary demands was proper staffing. Multiple statements from the New York State Nurses Association (NYSNA) emphasize the need for proper staffing to fulfill safe nurse-to-patient ratios for both parties’ safety.² The study’s insights support NYSNA’s demands for proper staffing, as it would also improve patient outcomes.^1,2

This retrospective cohort study used patient discharge records and daily ward-level staffing rosters from 8 general medical or surgical wards across 9 National Hospital Organization-affiliated hospitals in Japan.¹ Patients included were aged 20 years or older and were either admitted to or discharged from participating hospitals between April 1, 2019, and March 31, 2020. Patients were evaluated for in-hospital mortality, unplanned readmission within 7 to 30 days upon discharge from the same hospital, and length of stay (LOS), with propensity score matching (PSM) and multilevel models used to adjust for confounding factors.

There were 77,289 eligible hospital admissions included in the final analysis. The median patient age was 69.3 years, and 33,075 (42.8%) were female. Furthermore, 41,137 (53.2%) were admitted for surgery. The most common major diagnostic categories experienced by 16,688 (21.6%) of patients were diseases and disorders of the digestive system, the hepatobiliary system, and the pancreas.

There were 43,770 patients in the adequately staffed group and 33,516 in the understaffed group. The overall nursing hours per patient day (NHPPD) were 4.4, 2.6, and 1.79 for the 24-hour period, day shift, and evening and night shift, respectively.

The unadjusted in-hospital mortality rate was higher in the understaffed group when compared with the adequately staffed group during the 24-hour period (3.3% vs 2.5%; P < .001), the day shift (3.3% vs 2.5%; P < .001), and the evening and night shift, although this finding was not significant (2.9% vs 2.8%; P = .22). Similar rates were observed after PSM as well.

Seven-day readmission did not differ significantly before vs after PSM. However, patients who experienced understaffing during the day shift had higher rates of 7-day readmission when compared with the adequately staffed group (2.3% vs 2.1%; P = .04). Contrarily, the 30-day readmission rates were significantly higher in the understaffed group when compared with the adequately staffed group, but only during the 24-hour period (11.2% vs 10.5%; P = .01). There was no significant difference between the groups during the day shift or the evening and night shift.

LOS was also significantly longer in the understaffed group before and after PSM during the 24-hour period, the day shift, and the evening and night shift.

This was the first study to observe associations between nurse staffing and patient outcomes with a robust analytical approach based on large-scale patient administrative data. However, this study was limited because it used ward-specific medians as a proxy, but this approach may normalize low staffing, thus limiting comparability. Additionally, PSM reduced confounding; therefore, unmeasured factors such as nursing experience and team composition may have influenced results.

“Ongoing monitoring of daily nurse staffing and addressing understaffing relative to the current annual median or higher may contribute to improved patient outcomes,” the study authors concluded.

References:

1. Morioka N, Moriwaki M, Miyawaki A, Saville C, Fushimi K, Griffiths P. Hospital nurse understaffing and patient mortality, readmission, and length of stay. JAMA Netw Open. 2026;9(2):e2558235. doi:10.1001/jamanetworkopen.2025.58235

2. McCrear S. NYC nurses strike enters day 5 amid staffing, safety, and benefit disputes. AJMC. January 16, 2026. Accessed February 24, 2026. https://www.ajmc.com/view/nyc-nurses-strike-enters-day-5-amid-staffing-safety-and-benefit-disputes