Purpose: The purpose of this study was to investigate the relationship between the concentration of digestive system surgery and outcomes at a regional level in Japan, using time-series data.
Methods: We used nationwide data from 2008 to 2013, and analyzed the ten most common surgical procedures. The unit of analysis was secondary medical areas (SMAs), which cover several municipalities and provide medical services for common diseases. The concentration of surgery in these areas was measured using the Herfindahl-Hirschman Index (HHI) and the relationship between the concentration of surgery and length of stay in hospital (LOS) was analyzed, in accordance with surgical difficulty.
Results: There was a downward trend in both the HHI and LOS from 2008 to 2013. SMAs showing an upward trend in the HHI (increased concentration) were associated with a greater reduction in LOS than those showing a downward trend for eight surgical procedures. For three easy surgical procedures, increased concentration of surgery was significantly associated with a reduction in LOS. After adjustment for trends in the aging population and the surgical volume in 2008, an increasing concentration for three easy surgical procedures was significantly related to a reduction in the LOS.
Conclusion: Concentrating relatively easy surgical procedures at a regional level may be associated with a reduction in LOS.
Keywords: Gastrointestinal surgical procedures; Herfindahl–Hirschman Index; Surgical volume.