May 3rd 2005

Early sexual intercourse, condom use and sexually transmitted diseases

1998/99 to 2000/01 and 2003

An estimated 12% of boys and 13% of girls have had sexual intercourse by ages 14 or 15, according to a new study based on data that the teenagers reported to a national survey.

Using data from the National Longitudinal Survey of Children and Youth (NLSCY), the study found that characteristics associated with early sexual activity differed for boys and girls.

A separate study, also based on self-reported data, found that many young people may be putting their health at risk by having sex without a condom.

This second report is based on data from the 2003 Canadian Community Health Survey (CCHS). It examines sexual activity, number of partners and condom use among 15- to 24-year-olds, as well as their likelihood of reporting having been diagnosed with sexually transmitted diseases (STDs), now also referred to as "sexually transmitted infections."

In 2003, an estimated 28% of 15- to 17-year-olds reported having had sexual intercourse at least once in their lives. By ages 20 to 24, the proportion was 80%. One-third of sexually active 15- to 24-year-olds reported that they had had more than one sexual partner in the previous year.

In addition, about 3 in 10 young people who had sex with multiple partners in the past year had not used a condom the last time they had intercourse.

Multiple partners, condom use related to age

Young men were more likely than young women to report having had more than one sexual partner during the previous year. As well, 15- to 24-year-olds who had had intercourse by age 13 were significantly more likely to have had two or more sexual partners in the past year than were those whose first experience happened when they were older.

Sex without a condom was more common at older ages. Nearly 44% of sexually active 20- to 24-year-olds reported sex without a condom, compared with 33% of those aged 18 to 19, and 22% of those aged 15 to 17.

It is possible that those in the older age group are more likely to be in a long-term relationship with one partner, and so perceive condom use as less of a concern.


Note to readers

The study on early sexual intercourse is based on data from the 1996/97, 1998/99 and 2000/01 National Longitudinal Survey of Children and Youth (NLSCY). It uses a sample of 3,212 youths who were aged 14 or 15 in 1998/99 or 2000/01.

A second study, on sexual intercourse, condom use and sexually transmitted diseases among older teens and young adults, is based on data from the 2003 Canadian Community Health Survey. It uses a sample of 18,084 youths aged 15 to 24 in 2003.

Some data limitations should be noted. For example, the term "sexual intercourse" was not defined in the survey questions. What one respondent considers "sexual intercourse" may differ from another's interpretation. Also, the answers that survey respondents give to questions about matters such as sexual activity, smoking or drinking may not accurately reflect their behaviour.


When the impact of other factors that might influence condom use (such as current age, age at first intercourse, marital status) was taken into account, young women in Quebec and New Brunswick emerged as being more likely to engage in sex without condoms than their counterparts in Ontario.

STD risk linked to age

According to CCHS data, 4% of 15- to 24-year-olds who had had sex at least once reported having been diagnosed with a STD. The true figure is likely higher than reported because of a possible lack of symptoms or awareness.

Young adults aged 20 to 24 were significantly more likely than 15- to 17-year-olds to have been diagnosed with an STD. This is probably because the older group has had more years of being sexually active.

Similarly, early age at first intercourse also increased the risk. Those who had had sexual intercourse by age 13 were more than twice as likely to report an STD than were those who had waited until they were older.

Factors differ for boys and girls

The factors related to early sexual intercourse differed for girls and boys, according to NLSCY data.

The odds of early intercourse among girls were high for those who, at ages 12 or 13, had reached puberty or were not overweight.

Also, girls whose self-concept was weak at ages 12 or 13 were more likely than those with a strong self-concept to have had sexual intercourse by 14 or 15. The opposite was true for boys.

An association between smoking and early sexual intercourse was strong for both sexes, even when the impact of the other factors was taken into account. At ages 12 or 13, 26% of boys and 31% of girls reported that they had tried smoking cigarettes. Within two years, over one-quarter of this group reported that they had had intercourse.

As well, for girls, having tried drinking by ages 12 or 13 was associated with reporting having had intercourse by ages 14 or 15.

Drinking was not associated with early sexual activity in boys. However, significantly high proportions of boys who had a poor relationship with their parents at ages 12 or 13, or who were in a low-income family, reported having had sex by ages 14 or 15.

Young girls in the eastern provinces and Quebec were more likely to report being sexually active than were those in Ontario.

Definitions, data sources and methods: survey number 3225.

The articles "Early sexual intercourse" and "Sex, condoms and STDs among young people" are available in the May 2005 issue of Health Reports, Vol. 16, no. 3 (82-003-XIE, $17/$48; 82-003-XPE, $22/$63).

For more information about the article "Early sexual intercourse," contact Didier Garriguet (613-951-7187; didier.garriguet@statcan.ca), Health Statistics Division. For more information about the article "Sex, condoms and STDs among young people," contact Michelle Rotermann (613-951-3166; michelle.rotermann@statcan.ca), Health Statistics Division.

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