Revisiting systematic geographical variations in tonsils surgery in children in the Spanish National Health System: spatiotemporal ecological study on hospital administrative data.

Objective: To provide new evidence on how tonsils surgery in children has geographically varied over time in the context of the Spanish National Health System.

Design: Observational ecological spatiotemporal study on geographical variations in medical practice, using linked administrative datasets, including virtually all surgeries performed from 2003 to 2015.

Setting: The Spanish National Health System, a quasi-federal structure with 17 autonomous communities (ACs), and 203 healthcare areas (HCAs).