Environmental factors associated with the time to tuberculosis diagnosis in prisoners in São Paulo, Brazil

Environmental conditions play an important role in the high incidence of tuberculosis in prisons. We estimated the effect of environmental factors, including measurements based on cell dimensions, on the time to tuberculosis diagnosis in prison population of Brazil.

This is a retrospective cohort of 2,257 prisoners diagnosed with tuberculosis in 2014 and 2015. We collected environmental data from 105 prisons and linked with routine tuberculosis surveillance and prison data. We estimated tuberculosis-free survival time with Cox risk models, guided by a validated directed acyclic graph.

The median disease-free time was 1.71 years (95% confidence interval [95% CI] 1.64-1.78). Each 50% increase in occupancy-rate, increased the tuberculosis speed incidence by 16% (95% CI 8%-25%) in the first 2 years, and 9% (95% CI 3%-16%) up to 5 years. An increase in the cell area per person (ln[m²/person]) reduced the hazard of tuberculosis by 13% (95% CI 3%-23%) for up to 2, and 12% (95% CI 3%-21%) for up to 5 years.

Most tuberculosis cases were diagnosed within 2 years of incarceration. Prison overcrowding and physical space per person in the cell were associated with the tuberculosis-free disease time.

Interventions to reduce overcrowding or increase physical space are crucial to prevent tuberculosis in prisons.