Nurse staffing configurations and sickness absence in intensive care units: A longitudinal observational study

Background: Staff wellbeing in intensive care units is essential for quality patient care, and nurse staffing configurations can impact nurse sickness absence. The COVID-19 pandemic imposed additional strain on nurses, potentially affecting sickness absence rates. Objective: To examine the association between registered nurse staffing levels, skill mix, and staff sickness absence in intensive care units spanning prepandemic (01/19-02/20), early pandemic (03/20-02/21), later pandemic (03/21-02/22), and post-pandemic (03/22-12/22). Design: Longitudinal retrospective study Setting(s): Three National Health Service hospital trusts in England Participants: Five intensive care units with 6916 sickness episodes from staffing data. Methods: We linked staffing data from electronic rostering systems. Variables included registered nurse hours per patient day, proportion of senior staff nurses with largely hands-on clinical experience, management presence, and sickness absence rates. Generalised linear mixed models analysed associations between staffing configurations in the previous 28 days and sickness absence. Results: The mean sickness absences rate was 2.4%. When analysing all time periods collectively, an increase in registered nurse staffing by 1 standard deviation (SD) (11.0 hours per patient day) was associated with a 5% reduction in sickness episodes (incidence rate ratio [IRR]=0.95; 95% confidence interval [CI] 0.90-0.99, p=0.018); a 1 SD (15.1%) increase in the proportion of senior nurse hours per patient day was associated with a 22% reduction in sickness episodes (IRR=0.78; 95% CI 0.71-0.86; p<0.001). For management, the relationship exhibited a non-linear pattern, with both higher and lower levels of managerial presence, compared to the norm, being associated with increased sickness absence. The observed relationships changed over time, especially during later and post-pandemic periods. A 1 SD (11.7 hours per patient day) increase in registered nurse staffing was associated with a 19% reduction in sickness absence in the post-pandemic period (IRR 0.81; 95% CI 0.69-0.95, p=0.010). A 1 SD increase in proportion of senior nurse hours per patient day was associated with both reduced (IRR 0.60; 95% CI 0.48-0.74, p<0.001 later pandemic) and increased sickness absence (IRR 2.00; 95% CI 1.31-3.05, p=0.001 post pandemic). Conclusions: Sickness absence in intensive care units decreased with higher registered nurse staffing levels, although this relationship was most apparent post-pandemic. The presence of more senior registered nurses was generally associated with reduced sickness absence, although this relationship proved complex and varied across time periods. Pandemic conditions appear to have altered typical staffing-sickness patterns, with staff sickness being less influenced by workload during the acute pandemic phase.