A mean age for youthful sex

Carolyn Moynihan
24 Jun 2011
Reproduced with Permission

"Young people are having sex for the first time at younger and younger ages." "The average age at which American (British, Swedish, Australian...) adolescents begin sexual activity is 15 (16, 17…)." "HIV/AIDS education needs to take place at correspondingly young ages.."

How many times do we read statements like this in news stories and studies? And how informative are they, really? A letter published online in the Archives of Sexual Behaviour recently suggests that references to "average age" or "mean age" in studies about adolescent sexual behaviour can be quite misleading.

In a study of adolescents in Europe, for example, one reads that "compared with previous generations, young people (16-20 year-olds) were having intercourse for the first time at an earlier age, on average at 16.5 years of age". (Avery & Lazdane, 2008) A superficial reading could suggest that "most young people" are sexually active at that age, although the statement does not, in fact, tell us how many are sexually active.

It seems that researchers focussed on epidemics of HIV/AIDS and STIs are so keen to catch adolescents before they have any risk of contracting these diseases that they are at risk themselves of creating false impressions. And, one might add, pushing back the age for sex education into early childhood.

Jokin de Irala and colleagues at the University of Navarra, Spain, say in their letter that it is time to clear up the confusion generated not only amongst journalists but even amongst public health policy makers and health education managers -- not to mention young people themselves.

The task is not difficult; it requires that researchers report the proportion of the age group which is sexually initiated, not just the average age at which that occurred. When that is done, the big picture looks very different. De Irala and colleagues are doing an international study of high school students -- Project YOURLIFE -- that illustrates the point.

In what appears to be a ground-breaking study, they used data from questionnaires answered by 7011 students in El Salvador, Peru and Spain, and compared the actual percentages of young people who were sexually active at different ages with mean and median ages.

The researchers found that in each of the three sites, the majority of young people whose ages were close to any of the three measures of "mean age of first sexual intercourse" were not sexually active. For example, mean ages of first sex in El Salvador, Peru and Spain were 15, 14 and 16 years respectively whereas the proportion of youth from ages close to those means that were sexually active was 21 per cent, 9.6 per cent and 22 per cent respectively. (See table published with the letter.)

The authors of the letter comment:

"The extensive use of mean age of sexual initiation in the scientific literature and consequently in the media suggests that the potential for misleading interpretations is not being adequately taken into account. Studies that use mean age of sexual initiation usually use age ranges that do not take into account those who have first sex at older ages or who never have had sex at all. This essentially biases the interpretation of such means."

In conclusion they point out that greater precision in communicating facts about adolescent sex "can be of crucial help to health policy makers and health education managers who are trying to convey the importance of delaying sexual initiation among youth.

"We therefore encourage the use of the percentage of youth, at different ages, who have already initiated sexual relationships instead of the use of averages. This will reduce confusion, help avoid erroneous interpretations, and provide a much needed additional source of support to young people, all of which in time gives such public health policies a better chance of succeeding."

Amen to that.