Moderating effect of pre-exposure prophylaxis use on the association between sexual behavior and perceived risk of HIV among Brazilian gay, bisexual, and other men who have sex with men: a cross-sectional study (Preprint)

Abstract

Gay, bisexual, and other men who have sex with men (MSM) with higher perceived risk of HIV are more aware of and willing to use pre-exposure prophylaxis (PrEP). PrEP is an effective HIV prevention strategy, but there is a lack of data on how PrEP use might moderate the relationship between sexual behavior and perceived risk of HIV. Moreover, most studies have measured perceived risk of HIV via a single question.

We estimated the moderating effect of PrEP use on the relationship between sexual behavior and perceived risk of HIV, measured with the 8-item Perceived Risk of HIV Scale (PRHS), among Brazilian MSM.

A cross-sectional, online survey was completed by Brazilian Hornet app users >18 years old between February-March 2020. This analysis includes data from cisgender men who reported sex with men in the previous six months. We evaluated the moderating effect of current PrEP use on the relationship between sexual behavior, measured via the HIV Incidence Risk Index for MSM (HIRI-MSM), and perceived risk of HIV, measured by the PRHS. Higher HIRI-MSM (range 0-45) and PRHS scores (range 10-40) indicate greater behavioral risk and perceived risk of HIV, respectively. Both were standardized to z-scores for use in multivariable linear regression models.

Among 4,344 cisgender MSM, 448 (10.3%) were currently taking PrEP. Current PrEP users had a higher mean HIRI-MSM score (21.0 vs. 13.2, p<0.001) and a lower mean PRHS score (24.6 vs. 25.9, p<0.001) compared to those not taking PrEP. In the multivariable model, greater HIRI-MSM scores significantly predicted increased PRHS scores (β=0.28 [95%CI 0.25 to 0.32], p<0.001). PrEP use moderated the association between HIRI-MSM and PRHS score (interaction term β=-0.32 [95%CI -0.40 to -0.23], p<0.001), such that higher HIRI-MSM score did not predict higher PRHS score among current PrEP users.

Our results suggest current PrEP users have confidence in PrEP’s effectiveness as an HIV prevention strategy. PrEP’s effectiveness, its positive psychological impact, and the frequent HIV testing and interaction with health services required of PrEP users may jointly influence the relationship between sexual behavior and perceived risk of HIV among PrEP users.