Kids aren't having sex at younger and younger ages. Africans do not typically have more sexual partners than people in the West, even though HIV/AIDS has spread rapidly on their continent. Married people have more sex than the single—and marriage is not always a good defense against STDs.

All of these are findings of the first comprehensive global study of sexual behavior, published in <i>The Lancet</i> last week. The study's authors, led by Kaye Wellings of the London School of Hygiene and Tropical Medicine, reviewed survey data from 59 countries that had been collected since 1996 by researchers in medicine, public health, and social sciences. Wherever possible, Wellings and her team then compared the recent data to survey results collected over the previous two decades.

The conclusions? The study suggests that globally there has been less change in sexual behavior in recent decades than is often assumed. More people are having pre-marital sex, the authors say, but much of this is attributable to the rise in average marriage ages around the world. Although there are significant regional differences—the median age at which middle-aged men in Indonesia lost their virginity, for example, is 24.5 years—almost everywhere men and women lose their virginity when they are aged 15 – 19.

 Researchers note the surprising lack of clear link between sexual behavior and sexual health. High rates of sexually transmitted diseases, like AIDS, are not strongly associated with promiscuous populations. Instead, factors like education and condom use may keep the relatively promiscuous Westerners in better health than poorer counterparts.

What it means: This is the first time anyone has set out to do a large-scale study of sexual behavior all over the world. As a result, the study has great value not just in debunking myths about sex, but also in shaping sexual-health policy. The researchers note, however, that the data vary greatly from country to country. They caution that it is simply not possible to develop a sexual-health program that would fit every community. They stress that policy should focus on what they see as the underlying determinants of sexual health—poverty, mobility, and gender equality—not just individuals' sexual choices.

However, there are significant problems with the study's data. The study's authors say there are limited sources available from the Middle East and parts of Asia. Globally, men reported many more sexual partners than women—which suggests a tendency for women to under-report the number of people they sleep with or for to men over-report, or both. (Other explanations for the discrepancy, researchers suggest, is that women who sleep with many men, like sex-trade workers, are underrepresented in sexual-behavior surveys.) Still, the global study of sexual health goes a long way towards busting myths and providing information on which to base public-health interventions.

From the Archive:

Jun. 21, 2006: The "Promiscuity" Vaccine
Jun. 15, 2006: Where'd You Learn That?