WEDNESDAY, Jan. 16, 2002 (HealthDayNews) -- If you knew the odds of getting AIDS for each kind of sexual act, would you change your behavior?
Federal epidemiologists say they hope you would, which is why they estimate the risk levels for various sexual practices in a new study that appears in the January issue of the journal Sexually Transmitted Diseases.
However, one expert warns that relying on the numbers could spell trouble and knowing your partner's HIV status is probably the best protection against AIDS.
"Very few people . . . engage in only one type of sex," says Frank Edward Myers III, an epidemiologist with Scripps Mercy Hospital in San Diego who has studied AIDS. Even if a person's sex life is limited, he says, the research doesn't consider many variables.
However, study co-author Dr. Thomas Peterman says the report is just a starting point.
"The overarching main message is that there are a variety of ways that you can reduce your risk," says Peterman, who studies sexually transmitted diseases at the Centers for Disease Control and Prevention.
Peterman and his colleagues set out to figure out how different sexual activities affect the odds that someone will get AIDS, especially considering that many people have adopted so-called "safe" practices. "The question is how much impact that has had on their risk," he says.
The researchers examined the prevalence of HIV and AIDS (an estimated 20,000 people are infected in the U.S. each year), the risks of condom failure (estimated at 5 percent), and the accuracy of HIV tests. They assumed that 10 percent of homosexual men are HIV positive, and 1 percent of heterosexuals are.
Using a mathematical formula, they came up with a list of odds for various types of heterosexual sexual acts when compared to receiving oral sex, considered to be of very low risk.
The researchers say performing oral sex is twice as risky as receiving oral sex. When compared to receiving oral sex, insertive vaginal sex is 10 times more risky, insertive anal sex 13 times more dangerous, receptive vaginal sex 20 times more hazardous, and receptive anal sex 100 times more perilous.
The researchers also estimated that not wearing a condom is 20 times as risky as using one.
The researchers estimated that the risk of getting AIDS is one in 2,000, per act, for men who have receptive anal sex with men whose HIV status is not known to them. The risk fell to between one and 2.5 per 100,000 if the gay male took one safe-sex precaution, such as wearing a condom or making sure a partner tested negative for HIV. Gay men should clearly take more than one step to reduce their risk of being infected, Peterman says.
Condoms aren't the only key to safer sex, he adds: "It's pretty clear that you're better off testing your partner than you are ignoring (HIV) status and using a condom."
Myers says the odds analysis relies on some studies that are flawed because it's difficult to get accurate information about human sexual behavior and determine exactly how AIDS was transmitted to those who are infected.
For women, he says, sex may be riskier during pregnancy and menstruation. Lack of lubrication may raise risk levels, as may swallowing semen during oral sex, he says.
The study should not be taken literally, he says, but instead be considered a "general barometer" of sexual risks.
What To Do
Learn about HIV tests and what they mean from this fact sheet from the San Francisco AIDS Foundation .
From infection to the full-blown disease, AIDS usually follows a specific pattern in patients. Learn about what happens and when from Boston University.
