PrEP could reduce condom use by some gay men

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A substantial proportion of gay men say they would reduce their condom use if pre-exposure prophylaxis (PrEP) proves to be effective, US investigators report in the online edition of the Journal of Acquired Immune Deficiency Syndromes.

The investigators found that the availability of 80% effective PrEP could reduce inhibitions about unprotected sex. Their results also showed that it could lead men to view unprotected sex as having an acceptable level of risk.

“A better understanding of the emergent issues inherent in the provision of PrEP will allow for the development of both individual-level interventions supporting PrEP users and community-level interventions designed to increases awareness and acceptability of PrEP”, comment the investigators.



Amyl, butyl or isobutyl nitrite, are recreational drugs sniffed during sex to both intensify the experience and relax anal sphincter muscles.


Confounding exists if the true association between one factor (Factor A) and an outcome is obscured because there is a second factor (Factor B) which is associated with both Factor A and the outcome. Confounding is often a problem in observational studies when the characteristics of people in one group differ from the characteristics of people in another group. When confounding factors are known they can be measured and controlled for (see ‘multivariable analysis’), but some confounding factors are likely to be unknown or unmeasured. This can lead to biased results. Confounding is not usually a problem in randomised controlled trials. 

risky behaviour

In HIV, refers to any behaviour or action that increases an individual’s probability of acquiring or transmitting HIV, such as having unprotected sex, having multiple partners or sharing drug injection equipment.

PrEP involves the treatment of HIV-negative individuals with antiretroviral drugs to prevent infection with HIV. Laboratory and animal tests have had promising results. A number of clinical trials using PrEP are currently underway and some results are expected shortly.

There is considerable optimism about the impact PrEP could have on the transmission of HIV. However, some have cautioned that the availability of a biomedical method of prevention could lead some individuals to become less reliant on condom use and partner reduction to avoid HIV. It has been suggested that an increase in risky sexual behaviour could undermine the potential benefits of PrEP.

Two psychological mechanisms could lead to PrEP increasing sexual risk taking. The first is “behavioural disinhibition”. This means that individuals who desire unprotected sex would view PrEP as a substitute for behavioural control, or condom use.

It is also possible that PrEP could lead to “risk compensation”. Some individuals may consider that PrEP reduces the risk of HIV transmission to such an extent that they are willing to have unprotected sex when taking PrEP.

Little research has been undertaken into the potential impact of PrEP on sexual behaviour. Therefore investigators in New York designed a study involving 180 substance-using HIV-negative gay men who had had at least one recent episode of unprotected anal sex.

They completed a questionnaire about their use of club drugs (cocaine, ketamine, ecstasy, methamphetamine, GHB or poppers), sexual risk behaviour, and attitudes towards PrEP. The men also answered questions to assess behavioural disinhibition and risk compensation.

Researchers measured risk perception on a five-point scale using seven questions to assess the extent to which condom use was dependent on the participant's perception of risk in each individual sexual encounter.

The men had a mean age of 29 and were racially diverse. Only a minority of men (42%) had been to college, and 40% had an annual income below $20,000. The men reported a median of three high-risk sex acts in the previous 30 days, a median of two occurred when using club drugs.

Only 23% of the men had ever heard of PrEP. Three men reported ever having used PrEP. Two men said that they used it before having unprotected sex with a man of unknown HIV status; the third man indicated that he took PrEP because he knew his partner was HIV-positive.

A clear majority of men (69%) said that they would be likely to use PrEP if it was shown to be at least 80% effective.

Individuals who reported six or more risky sex acts in the previous 30 days were significantly (OR = 2.71; 95% CI, 1.15-6.40) more likely to report that they would use PrEP than those who reported fewer episodes of unprotected sex.

There was a clear relationship between a willingness to use PrEP and both prior sexual disinhibition (OR = 1.85; 95% CI, 1.24-2.75) and a reduced perception of risk (OR = 1.76; 95% CI, 1.08-2.87).

Of the men who said that they would be willing to use PrEP, 36% reported that its availability was likely to reduce their use of condoms.

Individuals who reported that PrEP would reduce their condom use were more likely to have a college degree (OR = 2.56; 95% CI, 1.19-5.47).

Dependency on club drugs was also associated with reporting that the availability of PrEP would reduce condom use.

The investigators also found evidence that reducing condom use because of PrEP was associated with both disinhibiton (OR = 1.76; 95% CI, 1.10-2.82) and risk compensation (OR = 2.48; 95% CI, 1.34-4.62).

After adjusting their results for potentially confounding factors, the investigators found that disinhibition (OR = 1.24; 95% CI, 1.05-1.45) and risk compensation (OR = 2.30; 95% CI, 1.15-4.6) remained significantly associated with PrEP availability and reduced condom use.

“Our findings underscore the importance of combining PrEP availability with behavioural interventions that target specific psychosocial factors…that are most relevant to high-risk populations”, comment the investigators.

They conclude, “PrEP has the potential to make an extraordinary contribution to the fight against HIV, but its implications for risk perception and behaviour must be fully acknowledged and understood.”


Golub SA et al. Preexposure prophylaxis and predicted condom use among high-risk men who have sex with men. J Acquir Immune Defic Syndr, advance online publication, 2010.