TABLE 4.
Adjusted Associations Between Nurse Staffing Practices and the Risk of Mortality*
| Cumulative Nurse Staffing Practices Measured Over All Shifts Since Hospital Admission (AIC=98,552) | HR (95% CI) | P |
|---|---|---|
| RN understaffing† (per 5% ↑) | 1.010 (1.002–1.017) | 0.009 |
| Non-RN skill mix‡ (per 1% ↑) | 1.004 (0.997–1.011) | 0.261 |
| Education mix§ (per 5% ↑) | 0.980 (0.965–0.995) | 0.008 |
| RN collective experience∥ (per 1 y ↑) | 0.993 (0.978–1.008) | 0.369 |
Bold values indicate statistically significant P<0.05 threshold.
*HRs are from a Cox proportional hazards regression model treating the current unit of hospitalization as a random effect and adjusting for patient characteristics on admission [age, age2, sex, Charlson Comorbidity Index (CCI), CCI2, severity of illness (Laboratory-based Acute Physiology Score, LAPS), LAPS2, type, year, and month of hospital admission], whether the current unit of hospitalization provides medical, surgical or intensive care, current shift (night, day, or evening), current unit occupancy, whether the current day is a weekend/statutory holiday or not, and the cumulative proportion of shifts spent in an intensive care unit since hospital admission, and the square of that cumulative proportion.
†Cumulative proportion of shifts with an observed number of RNs’ worked hours at least 8 hours below the expected unit-shift value according to the patient census (see the “Registered nurse understaffing” in the Methods section for details), represented in percent.
‡Cumulative proportion of non-RNs’ worked hours among all nursing staff’s worked hours relative to the unit-shift mean, represented in percent.
§Cumulative average baccalaureate-prepared RNs’ worked hours among all RNs’ worked hours relative to the corresponding unit-shift mean, represented in percent.
∥Cumulative mean number of years of experience held by all RNs who reported worked hours relative to the corresponding unit-shift mean, represented in years.
AIC indicates Akaike Information Criterion; CI, confidence interval; HR, hazard ratio; RN, registered nurse.