Age-period cohort analysis of AIDS incidence rates in Rio de Janeiro, Brazil, 1985-2009.

Cristina Pinheiro Nádia Rodrigues

doi:10.1186/1478-7954-11-22

Abstract

IntroductionThe long average incubation time from HIV infection to AIDS makes it difficult to estimate the recent tendencies of HIV from AIDS incidence data. The objective of this study was to investigate the effects of three temporal components in AIDS incidence in the state of Rio de Janeiro, Brazil - age, period, and cohort.MethodsAge-specific AIDS incidence rates per 100,000 from Rio de Janeiro (Brazil) were calculated for both sexes using five-year age classes from 1985 to 2009 based on reported data from the Notifiable Disease Information System of the Brazilian Ministry of Health and from census population counts. Multivariate negative binomial models were used to analyze the risk of AIDS by age, period, and birth cohort.ResultsFrom 1985 to 2009, AIDS incidence initially increased with age in each birth cohort and then decreased (except for individuals born from 1971–1979 to 1986–1994). High peaks in the rates in each birth cohort were detected in 1995–1999 for males and in 2000–2004 for females. Multivariate analysis showed the maximum risk of AIDS in the 30–34 age group and 1958–1962 birth cohort.ConclusionAge, birth cohort, and period effects all may have influenced the AIDS incidence rates over the period investigated. From 1985 to 1999, comparison of the tendencies (by age) of the period with the birth cohort revealed opposing tendencies in individuals older than 29 years and in the youngest age groups (0 to 14 years). From 2000 to 2009, a strong age effect can be observed in both sexes. Consistent changes in period tendency curves suggest the occurrence of period effects. A reduction in the intensity of the risk of AIDS can be observed after 2000–2004.

Highlights

The long average incubation time from human immunodeficiency virus (HIV) infection to AIDS makes it difficult to estimate the recent tendencies of HIV from AIDS incidence data
Materials and methods Information of reported cases of AIDS of residents of Rio de Janeiro by sex, age, and year of diagnosis recorded over the 25-year period from January 1, 1985 to December 31, 2009 was obtained from the Notifiable Disease Information System (SINAN/DATASUS) of the Brazilian Ministry of Health
This study revealed that gender, age, birth cohort, and period effects are important factors for explaining AIDS incidence rates in Brazil

Summary

Introduction

The long average incubation time from HIV infection to AIDS makes it difficult to estimate the recent tendencies of HIV from AIDS incidence data. The treatment coverage of antiretroviral therapy has expanded. Just over 8 million people in low- and middle-income countries were receiving treatment in 2011, with coverage reaching 54% (range 50–60%). It is estimated that 15 million people may be receiving treatment by 2015 [3]. Since 1999, the number of new infections has fallen by 19%. New HIV infections are declining in many of the countries most affected by the epidemic. Since 2004, more than 27,000 new HIV infections have been diagnosed and reported each year, resulting in a cumulative total number of over 370,000 HIV infections reported since the beginning of epidemic [8]

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