The correlation between surgical, anaesthetic and obstetric workforce and surgical volume: a modelling study

The Lancet Commission on Global Surgery has stated that two-thirds of the world's population does not have adequate access to surgical and anaesthesia care. Surgical, Obstetric and Anaesthetic (SAO) workforce and surgical volume (SV) are two of the six indicators recommended for monitoring and planning. This study aims to examine the correlation between SAO density and SV at the national level.

A cross-sectional ecological regression study was conducted with SAO workforce per 100,000 population and SV per 100,000 population, extracted from the World Bank Database. Countries that reported both indicators were included. If SAO was not available for the corresponding SV year, it was adjusted according to the population growth. A logarithmic regression model was used to describe the nonlinear association between SAO workforce density and surgical volume with SPSS. Model fit (R²) analysis, diagnostics, and a model implied marginal slope analysis were conducted.

A total of 57 countries were included, with 37 (64.9%) requiring adjustment. The fitted logarithmic regression model (y = 884 ln(x) + 685) had an R² of 0.524. At an SAO density of 10 per 100,000 population, the fitted model predicted approximately 2720 procedures per 100,000 population. At 20 and 40 SAO, 3333.7 (95% CI for fitted mean: 2917.2-3750.2) and 3946.5 (95% CI for fitted mean: 3470.7-4,422.3) procedures are expected, respectively. The marginal slope analysis of our model was progressively smaller at higher SAO densities.

This study provides empirical insights into the nonlinear relationship between SAO workforce density and surgical volume. The findings highlight the need to balance workforce expansion with wider health-system capacity and may contribute to the future development of more informative surgical planning and performance indicators.