Female and male differences in AIDS diagnosis rates among people who inject drugs in large U.S. metro areas from 1993 to 2007

Abstract

Purpose

We estimated female and male incident AIDS diagnosis rates (IARs) among people who inject drugs (PWID) in U.S. metropolitan statistical areas (MSAs) over time to assess whether declines in IARs varied by sex after combination antiretroviral therapy (cART) dissemination.

Methods

We compared IARs and 95% confidence intervals for female and male PWID in 95 of the most populous MSAs. To stabilize estimates, we aggregated data across three-year periods, selecting a period immediately preceding cART (1993–1995) and the most recent after the introduction of cART for which data were available (2005–2007). We assessed disparities by comparing IAR 95% confidence intervals for overlap, female-to-male risk ratios, and disparity change scores.

Results

IARs declined an average of 58% for female PWID and 67% for male PWID between the pre-cART and cART periods. Among female PWID, IARs were significantly lower in the later period relative to the pre-cART period in 48% of MSAs. Among male PWID, IARs were significantly lower over time in 86% of MSAs.

Conclusions

IARs among female PWID in large U.S. MSAs have declined more slowly than among male PWID. This suggests a need for increased targeting of prevention and treatment programs and for research on MSA level conditions that may drive differences in declining AIDS rates among female and male PWID.

Introduction

After the introduction of combination antiretroviral therapy (cART), there was a substantial reduction in the number of AIDS diagnoses in the United States, particularly among people who inject drugs (PWID) [1]; however, national trajectories of change in AIDS diagnoses have not been the same for female and male PWID [1], [2]. In 1995, PWID represented seven percent of persons diagnosed with AIDS among females and 19% among males [2]. In 2011, 20% of new AIDS diagnoses among females were injection related, whereas only 10% of AIDS diagnoses among males were from PWID [1]. During this time, we have estimated that PWID prevalence per 10,000 adult population in large U.S. metropolitan statistical areas (MSAs) also fell from 157 in the period from 1993 to 1995 to 133 in the period from 2005 to 2007 among males, and from 82 to 75 among females [3]. These data raise questions about changes in epidemiologic patterns of AIDS among female PWID and how these patterns may vary across geographic areas.

This article focuses on differences between female and male PWID in incident AIDS diagnosis rates (IARs) across MSAs. Analysis at the MSA level provides a useful lens through which to understand the historical and social factors that drive HIV burden in different locales. Several articles have found differences in HIV prevalence and AIDS mortality among PWID across MSAs, and this variation has been linked to MSA-level factors [4], [5], [6]. Previous research has also demonstrated that racial and/or ethnic disparities in AIDS diagnoses among PWID varied significantly across MSAs [7]. Although there is ample evidence demonstrating the success of cART in reducing morbidity and mortality in the United States [8], [9], the diffusion of cART and other important services may not have been uniform across MSAs and may have reached male and female injectors at different times. Disparities in the availability of cART and HIV care, as well as its accessibility to female PWID, may have resulted in significant sex differences in AIDS diagnoses across MSAs among injectors. In this article, we assess changes in IARs among female and male PWID across large MSAs between a pre-cART period (1993–1995) and a period well after cART was available (2005–2007).