Discussion
In this large, “real world” multicentre sample of SUs in England, there was overall only a weak association between weekend admission and mortality, but this masked important variation between SUs in their organisation of weekend care and mortality outcomes. There was wide variation in the intensity of clinical staffing on weekends, and evidence that a significant proportion of SUs were already providing weekend staffing levels similar to those during the week. After adjusting for patient-level and organisational variables, there was no evidence that having stroke specialist physician ward rounds 7 d/wk (as opposed to fewer than 7 d/wk) independently influenced an association between weekend admission and mortality. By contrast, there was evidence of a dose–response relationship between mortality and nursing ratios on the weekend (with lower nurse/bed ratios being associated with higher mortality risk), which was consistent in a variety of models adjusting for other potential confounders. These observational data support the hypothesis that nursing levels are an important mediator of excess mortality for patients admitted with stroke on a weekend.