Friday May 18, 2012
In an article from the upcoming June issue of the American Journal of Public Health, two scientists from UNC Chapel Hill analyzed data from the National Longitudinal Study of Adolescent Health to see how and when today's teenagers begin to experiment with sex. The study, which collected data from almost 14,000 teenagers, is one of only a few large surveys to examine not just vaginal intercourse but other types of sexual activity.
The researchers found that, by the age of 18, 67.4 percent of teens had experienced oral sex, 75.2 percent had experienced vaginal intercourse, and 10.7 percent had experienced anal sex. The researchers also explored what type of sex each teenager tried first. They were hoping to answer questions such as whether teens see oral sex as a safer alternative to intercourse and thus decide to experiment with it before exploring other things. However, what they found was somewhat surprising. While 14.7 percent of the teens did have oral sex before they had intercourse, 33.3 percent had vaginal intercourse first, and 32.6 did both at the same age. That suggested that, for most teens, oral sex probably isn't used as a way to delay other sexual activities.
Interestingly, if not surprisingly, the researchers also found that there were some significant racial and ethnic differences in the ways that teens initiated and experimented with sexual activity. For example, 62 percent of Black teens had vaginal intercourse first, compared to 26 percent of White teens and 38 percent of Hispanic teens. However, White teens were significantly more likely to have had oral sex than Asians, Hispanics, or Blacks.
Wednesday May 16, 2012
According to a paper published last week in The Lancet: Oncology 16 percent of cancers are caused by infection with a virus - meaning there are more than two million new cancer diagnoses attributable to infection each year. This number varies from country to country - in Sub-Saharan Africa almost one third of cancers have a viral origin - but no matter how you look at things this represents a fundamental change in the public conception of cancer. It's still a condition where cells are growing out of control, but now we know that many of them have a trigger.
Although it might not sound like it at first, this is actually good news. Two of the most common triggers - hepatitis B and HPV - are preventable by vaccine. A third, Helicobacter pylori, can be treated with antibiotics. This means that there are real, tangible ways for doctors to reduce the impact of cancer on human health.
Monday May 14, 2012
Last week, the FDA approved the use of
Truvada for
pre-exposure prophylaxis in groups who are at high risk for contracting
HIV through sexual contact - gay and bisexual men and the domestic partners of HIV infected individuals. As I've
said before, I have extremely mixed feelings about the concept of pre-exposure prophylaxis. I'm worried that people may use it as an excuse to forgo practicing
safe sex. I'm concerned that misuse might lead to a problem of drug resistance. It bothers me that people might change the way they think about protecting themselves from HIV.
Still, I think that the approval is probably a good thing, for one specific reason. Some people are already using the drug off-label for PrEP. At least this way, maybe their doctors will be monitoring them. With any luck, that might even include doing a better job of providing regular HIV testing.
Friday May 11, 2012
The
HPV vaccine is one of the most important sexual health discoveries of the past few decades. Being able to prevent
HPV-related cancers should be a triumph of science, but uptake of the vaccine has never been great. Unfortunately, in recent years, it seems like some measures of vaccinations have only been getting worse. An early view article just published in the journal
Cancer has shown that, in the years between 2006 and 2009, the number of young women completing the full vaccination schedule actually went steadily down.
With the exception of the subgroup of women over the age of 27, who were paying for the shot out of their pockets and as such presumably highly motivated to seek protection, the number of women who managed to get all three shots dropped by more than 20 percent over the study period. Ironically, during the same period doctors actually started to do a better job of getting young girls to begin the vaccine series, there just was less follow through. That's a shame because a single shot is not enough. The HPV vaccine is a three shot series not (just) because the vaccine companies want to make money, but because it takes multiple, correctly timed, exposures to the vaccine to maximize the benefits.
