Life & Family | Family

(Hint: It´s later than you think)

by Carlos Polo | Source: Population Research Institute

The age atwhich teenagers begin to engage in sexual activity is a critical variable forthose who would make public policy in the health field. Early onset of sexualactivity is associated with higher rates of sexually transmitted infections(STIs), teen pregnancy, depression, suicide, and other adverse consequences.

However, just how todetermine this age can be difficult to determine, and some commonly usedcalculations can lead to grossly erroneous results, as a groundbreaking studyby Dr. Jokin de Irala has now demonstrated.

Dr. Irala carried out amulti-national survey of 7,011 adolescents of both genders from private andpublic schools in Peru, El Salvador and Spain to gather data on the age offirst sexual intercourse. In his study, which used a significantly largersampling of adolescents than similar surveys, De Irala calculated the age atfirst sexual intercourse using both of the methods commonly relied upon: “themean age at first sexual intercourse” and “proportions having already had sexat given ages.”

It turns out that thesecond formula—the proportions having already had sex at given ages—shows thatmost adolescents are chaste for far longer than the sex educators, and themedia, would have us believe.

“Average age at firstintercourse, obtained from published epidemiological studies about sexuality,are often presented by the media in such a way that ignores the real meaning ofthe data. Those who rely upon the media for information, such as the generalpopulation and the young people themselves, can be misled,” De Irala states.

What Dr. Irala isreferring to is the claim, frequently repeated by the mass media, that “themean age at first sexual intercourse is 15 years old.” This claim frequentlysurfaces in the debates on how to prevent AIDS, when it is invariably assertedthat the majority of adolescents at 15 years old have engaged in sexualactivity. But this is simply not true. The majority are, the data show, stillchaste at that age.

Of course, if publichealth officials believe that middle school-aged children are having sex, theywill begin to push all kinds of programs in the schools that will have theperverse effect of encouraging children who are not sexually active to becomeso. This will have an adverse effect on the health of adolescents. In the caseof AIDS, it could even be fatal.

Why is “mean age atfirst sexual intercourse” misleading?

It is misleading becauseit collapses the data into a single number. When someone reads that “the meanage at first sexual intercourse is 15 years old,” they assume that the greatmajority of adolescents have had sexual intercourse at 15 years old. But thisis simply not true. When you look at the complete data, as Dr. Irala has done,you realize that proportion of adolescents 15 years of age who have already hadsex is only 20 percent!

The most common mistakemade in the other studies that Dr. Irala examined is using only the individuals who havealready had sexual intercourse at a given age to determine the meanage at first sexual intercourse. This approach results in a number that onlydescribes the sexually active part of the population of adolescents. But if youconsider the entire universe of adolescents—both those sexually active andthose who are not—the results are very, very different.

De Irala's studydemonstrates this very clearly. In the three countries he examined, “the meanage at first sexual intercourse” is about 15 years old. But now look at Table 1below, the calculation of the “proportions having already had sex at givenages.” Sexually active adolescents under the age of 18 are actually in theminority!

Age	Percentage sexually active at this age
	El Salvador	Peru	Spain
13	6.7	4.4	-
14	13.8	9.6	-
15	20.9	17.0	-
16	26.6	21.4	21.7
17	32.0	29.4	34.8
18	38.0	40.0	62.9
19	45.5	-	78.0
20	-	-	79.5

In a personal interview,Jokin de Irala explained to PRI how even an expert can fail to appreciate how “medianage of first sexual intercourse” greatly exaggerates the percentage who aresexually active at given ages. “Even most social scientists fail to appreciatethis problem,” he told us. “This slanting of the data should now be recognizedfor what it is, and this approach abandoned, by any researcher who wants tocarry out a reliable investigation into adolescent sexual behavior,” he added.

Public healthorganizations like HHS, USAID, UNAIDS, HRRS, etc., need to rethink theirassumptions about the proportion of adolescents who are sexually active.Believing—wrongly—that the majority of adolescents are sexually active at 15years old, they impose condom distribution schemes and sex education courses onkids at ever younger ages.

At the same time theyrefuse to consider abstinence as a viable sexual behavior because they arealready convinced that “the majority does it.” If these public health organizationsrecognized that in reality only 20% of 15-year-olds are sexually active,perhaps their priority would shift to strengthening the decision of the other80% of adolescents to not have sex. (Or perhaps they wouldn't, since the goalof at least some of those who work in these organizations is to convinceinnocent children to have sex as early and as often as possible.)

Responsible public policymakers need to know that only a fraction of 15-year-olds are sexually active.They need to know that it is counterproductive, even dangerous, to distributecondoms and contraceptives to all adolescents. They need to know that suchprograms only produce more adolescents having sex in circumstances that putthem at emotional, physical, and moral risk.

Source: De Irala J, OsorioA, Carlos S, Ruiz-Canela M, López-del Burgo C. “Mean age of first sex: Do theyknow what we mean?” Arch Sex Behav 2011. DOI 10.1007/s10508-011-9779-4