[Differential seasonality in surgical waiting list discharges in Spain: implications for management]

To analyse the seasonal variability of surgical procedures with guaranteed maximum waiting times with a view to figure out whether there are differences between urgent admissions and need-sensitive procedures, and those supply-sensitive.

Retrospective longitudinal observational study with administrative data on hospital episodes of the National Health System for 14 autonomous communities, years 2003 to 2022, aggregated monthly. The elective supply-sensitive surgical procedures with guaranteed times were selected. Then, as to conduct, the comparative analyses, we selected need-sensitive elective procedures for aortic-coronary bypass surgery in patients over 40 years of age, percutaneous transluminal coronary angioplasty in patients over 40 years of age, and breast cancer surgery in adult women up to 85 years of age to compare differences in seasonal variability. Finally, in order to get a basal level of seasonal variation we used emergency admissions for hip fracture in patients over 65 years of age and admission for acute myocardial infarction in patients over 40 years of age. A multiplicative decomposition of the series was applied to calculate the seasonal rate of change, and a placebo test was applied to test the seasonal variability of health care delivery across comparison groups.

Supply-sensitive elective surgery showed a marked seasonal variability, with rates of variation above 1.20 in months such as February, March, May and June, and very low values in the summer months, 0.42 in August. The placebo test confirmed significant differences with respect to the expected distribution according to working days. In contrast, in those need-sensitive procedures and emergency admissions, the seasonal variability was found to be almost non-existent.

A reasonable management objective for hospitals could be to reduce the monthly variability in elective supply-sensitive surgical activity through improving indication, re-organizing of human resources and incentives to reduce activity.