Ecological analysis examining the association between census tract-level incarceration and reported chlamydia incidence among female adolescents and young adults in San Francisco.

OBJECTIVES Incarceration has been linked to increased risk of sexually transmitted infections (STIs). We conducted a census tract-level ecological analysis to explore the relationship between neighbourhood incarceration rates and chlamydia incidence among adolescent girls and young women under age 25 in San Francisco in 2010 to focus public health efforts in neighbourhoods at risk. METHODS Female chlamydial cases under age 25 that were reported to the San Francisco Department of Public Health in 2010 were geocoded to census tract, and chlamydia incidence was calculated. Addresses of incarcerated individuals were geocoded, and census tract-specific incarceration was estimated. American Community Survey data from 2005 to 2009 provided tract-specific survey estimates of demographic and socioeconomic characteristics of communities to allow for evaluation of potential census tract-level confounders. A Poisson mixed model was used to assess the relationship of census tract-level incarceration rate with chlamydial case rate. RESULTS Accounting for spatial dependence in neighbouring regions, there was a positive association between incarceration rates and chlamydia incidence in young women under age 25 in San Francisco, and this association decreased as poverty increased, after controlling for other risk factors in the model. CONCLUSIONS This ecological analysis supports the neighbourhood role of incarceration in the risk of chlamydia among young women. These results have important implications for directing limited public health resources to local areas at risk in order to geographically focus prevention interventions and provide improved access to STI services in specific neighbourhoods with high incarceration rates.