Staffing levels and hospital mortality in England: a national panel study using routinely collected data

BackgroundMost studies investigating the association between hospital staff levels and mortality have focused on single professional groups, in particular nursing. However, single staff group studies might overestimate effects or neglect important contributions to patient safety from other staff groups. We aimed to examine the association between multiple clinical staff levels and case-mix adjusted patient mortality in English hospitals. Methods and FindingsThis retrospective observational study used routinely available data from all 138 National Health Service hospital trusts that provided general acute adult services in England between 2015 and 2019. Standardised mortality rates were derived from the Summary Hospital level Mortality Indicator dataset. Estimates for the effect of clinical staffing from the single staff models were generally higher than estimates from models with multiple staff groups. Using a multilevel negative binomial random effects model, hospitals with higher levels of medical and allied healthcare professional (AHP) staff had significantly lower mortality rates (1.04, 95%CI 1.02 to 1.06, and 1.04, 95%CI 1.02 to 1.06, respectively), while those with higher support staff had higher mortality rates (0.85, 95%CI 0.79 to 0.91 for nurse support, and 1.00, 95%CI 0.99 to 1.00 for AHP support), after adjusting for multiple staff groups and hospital characteristics. Estimates of staffing levels on mortality were higher in magnitude between- than within-hospitals, which were not statistically significant in a within-between random effects model. ConclusionsWe showed the importance of considering multiple staff groups simultaneously when examining the association between hospital mortality and clinical staffing levels. Despite not being included in previous workforce studies, AHP and AHP support levels have a significant impact on hospital mortality. As the main variation was seen between-as opposed to within-hospitals, structural recruitment and retention difficulties coupled with financial constraints could contribute to the effect of staffing levels on hospital mortality.