Area-level socioeconomic variables associated with territorial disparities in tuberculosis notification rates in metropolitan France: a Bayesian ecological analysis.

Background: Although France is considered a low tuberculosis (TB) incidence country, TB remains a significant public health issue in certain high-risk groups and geographic areas, potentially linked to socioeconomic determinants. This study aims to assess the associations between TB notification rates and area-level socioeconomic variables in metropolitan France.

Methods: We conducted an ecological spatial study using TB cases reported to the French national surveillance system from 2008 to 2019. Using Bayesian Poisson regression, we modeled TB case counts at the ZIP code level. Standardized notification rates were estimated through indirect standardization by age, sex, immigration status, and housing type. The model included ZIP code level socioeconomic variables and a spatial random effect to account for spatial autocorrelation and residual variations in notification rates, which may relate to territorial disparities in reporting completeness.

Results: The study included 55,330 reported TB cases across 4478 of 5534 ZIP codes in metropolitan France. All tested socioeconomic variables showed varying associations with TB. In the multivariable model, an increase in population density from 'Low' to 'High' was associated with a 30% increase [95% credible interval (CrI): 21%, 38%] in standardized TB notification rates. An increase from the first to the ninth decile in the unemployment rate among those aged 15-64 was associated with a 28% increase (95% CrI: 19%, 37%). Similarly, an increase in the proportion of overcrowded households was associated with a 19% increase (95% CrI: 11%, 28%). Conversely, an increase in median household income was associated with a 7% decrease (95% CrI: 1%, 11%).

Conclusions: Our findings suggest that TB notification rates are independently associated with material deprivation, such as unemployment and low income, as well as crowded settings, including overcrowded households and densely populated areas. Enhancing TB control in metropolitan France could involve targeted outreach programs for screening and treatment in materially deprived areas, characterized by high unemployment rates and low median incomes, and adopting a 'Health in All Policies' approach to address urban and household crowding.