Leprosy decline in Amazonas State, Brazil

Abstract

Objective To analyse the leprosy case detection rates in Amazonas State, Brazil, by age group from 1980 to 2009. Method The historical data series of leprosy cases by age group from 1980 to 2009 were fitted as a function of time using Poisson regression models. Relative annual reduction in the detection rate (RAR) by age group was estimated as one minus the exponential of the estimated regression coefficient for time. To compare the regression coefficients, we used their 95% confidence interval. Results The relative annual reduction varied from 9% in the age group of 0-4years to 1% in the age group of 60-69years. There was a declining trend of the RAR in the younger age groups that disappeared after 29years of age. The detection rate in people >29years old declined very little over time, with no statistically significant difference between age groups. Conclusion Our findings show a reduction in the infection risk in the last 30years and a birth cohort effect: cohorts born in more recent years faced smaller risks of leprosy infection than older cohorts. © 2011 Blackwell Publishing Ltd.