Although extensive changes in risk behaviors have been documented among men who have sex with men (MSM), large randomized clinical trials in which the study outcome is HIV infection -- the most direct measure of an intervention's effect -- have not been conducted. The EXPLORE study is the first randomized trial conducted among MSM in the United States designed to test the efficacy of a behavioral intervention in preventing acquisition of HIV by using HIV infection as the endpoint. The authors describe risk prevalence rates at baseline among the study's large multisite cohort of MSM in an attempt to identify risk behaviors that may be continuing the HIV epidemic. Furthermore, data are presented on relationships of specific HIV risk behaviors to the following known risk factors: type and number of sexual partners and alcohol and drug use.
From January 1999 to February 2001, HIV-negative MSM were recruited in six U.S. cities: Boston, Chicago, Denver, New York, San Francisco and Seattle. Men were considered eligible if they were age 16 or older and reported having engaged in anal sex with one or more men during the past year. Among the 4,862 individuals screened, 4,716 (97.0 percent) were found to be negative for HIV antibodies and eligible for study participation; 4,295 (91.1 percent) enrolled.
Information on sexual behaviors during the previous six months with partners of each serostatus type (negative, positive, and unknown) was collected. The median number of male sex partners reported during the six months before screening was seven. Just over 42 percent reported having had 10 or more male partners during that period. About half the men reported that they were involved in a primary relationship with a male sex partner. Among the three different partner serostatus classifications, the largest proportion of men reported having partners of unknown status.
With regard to specific sexual risk, 45.2 percent of the men reported engaging in unprotected receptive oral sex with ejaculation, 48.0 percent reported engaging in unprotected receptive anal sex, and 54.9 percent reported engaging in unprotected insertive anal sex. One-fifth (21.2 percent) of the men reported engaging in all three behaviors.
For alcohol and drug use, 26.2 percent of the men reported drinking alcohol at least three days per week, and 10.6 percent were heavy drinkers (i.e., they consumed at least four drinks per day or consumed an amount equal to six drinks per occasion). Marijuana was the noninjection drug most likely to be used (46.3 percent of men), followed by poppers (amyl nitrates) (36.6 percent); hallucinogens, including ecstasy (24.0 percent; cocaine (19.3 percent); and amphetamines (12.9 percent). Ten percent of the men reported recent injection drug use.
Almost 13 percent of the men reported having had a specific STD in the six months before they enrolled in the study. The STD most frequently reported was chlamydia (4.2 percent), followed by gonorrhea (3.3 percent), genital or rectal warts (3.1 percent), and anogenital herpes (2.6 percent). Nonspecific STD symptoms were reported by 10.6 percent of the men.
The researchers found that drug and alcohol use were significantly associated with unprotected sex. The EXPLORE baseline data indicate that men with multiple partners of unknown and positive status were engaging in just as much unprotected anal sex as were men with only one primary partner. EXPLORE also showed that men with multiple partners positive for HIV antibodies were more likely to report unprotected receptive anal sex.
These data support the need to understand the relationship status and known or perceived serostatus of potential partners before counseling MSM about sexual risk. Interventions targeted at MSM also need to directly address use of alcohol and drugs. Of particular concern is the high proportion of participants who reported drug use and engaging in unprotected anal sex with partners of unknown serostatus -- the sexual behavior with the highest risk. Thus, "the EXPLORE baseline data, in conjunction with information on the ongoing resurgence of STDs, increased HIV incidence rates, and changes in risk behaviors among MSM in many U.S. cities, emphasize the continued need for effective behavioral strategies designed to prevent HIV infection among MSM."
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This article was provided by CDC National Prevention Information Network.
It is a part of the publication CDC HIV/Hepatitis/STD/TB Prevention News Update.