Definitions for derived variables for ED and hospital workload and staffing factors used in this analysis
| Variable | Variable type | Definition |
| IMD score | Categorical | Quintile 1 (least deprived)—IMD score <24.94 Quintile 2—IMD score 24.94–34.75 Quintile 3—IMD score 34.76–41.05 Quintile 4—IMD score 41.06–48.33 Quintile 5 (most deprived)—IMD score>48.33 |
| ED bed occupancy rate | Continuous | Ratio of patients in the department in any given hour during the day, to the number of adults beds in the ED (see table 1) |
| Arrival intensity | Continuous | Raw number of patients arriving in the department during each hour of the day |
| Ambulance arrival intensity | Continuous | Ratio of patients arriving in the department by ambulance in any given hour, to the total number of patients arriving in that hour |
| ‘Left without being treated’ | Continuous | Number of patients who left without treatment in any given hour as a proportion of all those leaving within the same hour |
| Late discharge | Binary | Positive score (1) applied to each patient who left the department between 230 and 240 min of initial attendance time. This measure was derived to investigate the impact of the 4-hour quality indicator on admission |
| Inpatient bed occupancy rate | Continuous | Proportion of general and acute medical beds occupied within each hospital, each day of the month. Figures are reported at 9:00 every day |
| Consultant on duty | Binary | Positive score (1) applied to each record for which a consultant was on duty at the time of arrival in the ED |
ED, emergency department; IMD, Index of Multiple Deprivation.