One of the anxieties in relation to ‘treatment as
prevention’ is that it may discourage people with HIV from using condoms and
other prevention methods. However, a meta-analysis has found no increase in risk taking
in people who are taking antiretroviral treatment, compared to other people
with HIV. In fact, people on treatment had less unprotected sex and fewer
sexually transmitted infections.
The study by Joseph Doyle and colleagues was presented to
the 7th International AIDS Society Conference on HIV Pathogenesis,
Treatment and Prevention in Kuala Lumpur this week.
One important caveat is that the researchers examined
studies from all parts of the world and at any time since the introduction of
antiretroviral therapy, with only some of them gathering data in recent years. However,
understandings of the meanings and benefits of taking HIV treatment are
changing. No studies related to people specifically prescribed antiretrovirals
for prevention purposes.
The researchers identified all previous studies which met a
predetermined criteria and pooled their results. Relevant studies were of
HIV-positive adults, with some taking antiretroviral therapy and some not,
providing information on unprotected sex, diagnoses of sexually transmitted
infections or unsafe injecting. The methodology of the Cochrane Collaboration
Fifty-five different studies provided data on self-reports
of unprotected sex or inconsistent condom use, with over 30,000 participants.
The pooled data showed that people on treatment were 28% less likely to report
unprotected sex than people not taking treatment (odds ratio 0.72, 95%
confidence interval 0.63 – 0.81). However, there was considerable heterogeneity
in these results – the findings varied considerably from study to study.
Moreover, people taking treatment were less likely to report
unprotected sex with a person of unknown or negative HIV status (odds ratio
0.57, 95% confidence interval 0.45 – 0.71).
Eleven studies with around 16,000 participants had
information on diagnoses on sexually transmitted infections. Again, the results
suggested that people on treatment were less likely to acquire an infection
(odds ratio 0.58, 95% confidence interval 0.33 – 1.01), although this was not
quite statistically significant.
These results were again quite heterogeneous, but
essentially because of a single study with very different results to the others. The
researchers felt justified in excluding this one from a further analysis. With
this study removed, the results became statistically significant (odds ratio
0.48, 95% confidence interval 0.38 – 0.61).
Only four studies, with 1600 participants, provided
information on unsafe injecting practices (lending, borrowing or re-use). This
analysis showed that people on treatment were neither more nor less likely to
have unsafe practices (odds ratio 0.90, 95% confidence interval 0.60 – 1.35).
The researchers say that the lower levels of risk behaviour
reported by people on treatment should be interpreted cautiously, as this data
cannot tell us anything about the causal relationships.
While it is possible that the counselling and support
associated with engagement with healthcare help individuals to limit their risk
taking, it is equally possible that the causation could run the other way – people
who have more stability in their lives or who are more risk averse may be more
likely to go on treatment.
But the data remains reassuring. “Strategies to scale up use
of treatment in the context of care are unlikely to adversely affect risk-taking
behaviour,” the authors conclude.