The Context of HIV Risk Among Drug Users and Their Sexual Partners

seropositivity and reported NMPD use were reported in both cohorts,
with users of all categories except barbiturates (downers) showing odds
ratios with 95 percent confidence intervals greater than 1 for prevalent
HIV infection. These odds ratios ranged from 1.6 (CI=1.3-2.0) for any
NMPD use in the MACS cohort to 2.0 (CI=l.2-3.2) for marijuana use
and 2.9 (CI=1.9-4.5) for popper use among the Boston Partners Study
(Seage et al. 1992).
Association of NMPD Use with Sexual Partners and Prevalence of
HIV Infection. All three of these studies have demonstrated an increased
likelihood of HIV infection among those men reporting the use of certain
NMPDs or combinations. Since the likelihood of becoming HIV infected
is highly dependent on the numbers of partners with whom unprotected
intercourse is engaged in, these analyses have controlled for either the
numbers of sexual partners or specific practices. When this is done, it is
consistently observed that the use of poppers and/or insufflated cocaine
are associated with increased prevalence of HIV infection beyond that
expected on the basis of numbers of partners or potential anal exposures.
The investigators in the Boston Partners Study reported a particularly
strong effect on risk of HIV infection among men who reported always
using poppers whenever engaging in RAS. These men, who comprised
approximately 10 percent of the study group, were almost 34 times more
likely to be HIV infected than men with no history of unprotected RAS or
popper use, and three times more likely to be HIV infected than men who
only sometimes combined unprotected RAS and poppers. These and
other findings (summarized below) have led to the suggestion by Seage
and colleagues that the use of certain NMPDs, most notably poppers,
during UAI may actually increase the likelihood of HIV infection for any
given exposure (Seage et al. 1992). This possibility and possible
biological mechanisms for such an interaction are discussed below.
Association of Prior Change in NMPD Use and Changes in High-
Risk Sexual Behavior and Incidence of HIV Infection. Among men
in the Chicago MACS/CCS cohort, those who reported the initiation of
popper use were significantly more likely to lapse to unprotected RAS
during the same 6-month period (Ostrow et al. 1993). Of particular
interest in terms of potential mechanisms was the finding that the
association was specific for lapsing and was not evident in the reverse
direction (e.g., men giving up popper use did not exhibit greater
propensity to move from unprotected to protected anal intercourse), and
was only observed for receptive (not insertive) anal sex with
nonmonogamous partners. While not accounting for all or most of the
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