Do Higher Hospital-wide Nurse Staffing Levels Reduce In-hospital Mortality in Elderly Patients with Hip Fractures: a Pilot Study

Background: There is increasing recognition that lower nurse staffing levels are associated with higher morbidity and mortality among medical and surgical patients. The degree to which this applies to elderly patients with hip fractures is unclear.

Questions/purposes: We conducted a pilot study using administrative data as an initial step in investigating the relationship between nurse staffing levels and in-hospital mortality among elderly patients with hip fractures.

Patients And Methods: We retrospectively reviewed administrative data for 13,343 patients 65 years or older with a primary diagnosis of hip fracture admitted to 39 Michigan hospitals between 2003 and 2006. We used logistic regression to calculate the change in predicted probability of in-hospital death conferred by differences in the hospitals' overall number of full-time equivalent registered nursing staff (FTE-RN) per patient day. Regression models controlled for patient age, gender, and comorbid conditions; hospital characteristics including teaching status, hip fracture volume, and income/racial composition of the hospital's zip code; and seasonal influenza.

Results: We found an association between hospital-wide nurse staffing levels and in-hospital mortality among patients with hip fractures. The odds of in-hospital mortality decreased by 0.16 for every additional FTE-RN added per patient day, even after controlling for covariates. This association suggests the absolute risk of mortality increases by 0.35 percentage points for every one unit decrease of FTE-RN per patient day, a 16% increase in the risk of death.

Conclusions: Decreased hospital-wide nurse staffing levels are associated with increased in-hospital mortality among patients admitted with hip fractures. These observations indicate the need for further studies to characterize this relationship for staffing of units caring for patients with hip fractures.

Level Of Evidence: Level III, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.